Ls1 Engine Build - My First Stroker Part 4
Our project Trans Am's homebuilt 383 LS1 roars to life - will we have ourselves one helluva hot street/strip ride?
From the February, 2009 issue of GM High-Tech Performance
The time has finally come: ever since we began this LS1 stroker build in our August 2006 issue, we've been forcing readers to hold their collective breaths; the completion of our hands-on, home-grown engine still months away. With a bulletproof Lunati rotating assembly, bumpy-yet-streetable Lunati Voodoo cam, and high-flow 11-degree heads from ET Performance, we've held high hopes for this garage-built mill. These expectations have extended both to performance output, as well as our ability to successfully demonstrate how a driven do-it-yourselfer can save some dough and reap a bunch of satisfaction by assembling a hi-po Gen III with his own two hands.
When we left you last time, we'd bolted this new 383-inch motor into our 2001 Trans Am and were just about to hit the starter. We've done that, and having completed a thorough break-in, went ahead and got some dyno and preliminary track results for you. We've also added up the dollars spent on this project, and have done some research in an attempt to draw some comparisons to other options for stroking your ride. All of that information will appear below; but first, in the do-it-yourself spirit of this story series, we'd feel the job wasn't complete if we didn't give you a few final hints and tips for engine startup, break-in, and tuning. After all, our target audience has been readers who may be looking to tackle their very first engine build--these issues all go along with the territory. In the spirit of following the path that typical do-it-yourselfers may trod, read on!
Not one to show its full hand,...
Not one to show its full hand, our stroked LS1 chooses to reveal only some of the power that's on tap. While features like our MSD coils, Speed Inc. fuel rails, and not-currently-active ZEX nitrous system make it clear that this is no showroom stocker, there's no outward way to tell that this engine sports anything more than 346 cubes. Also noteworthy is that we've retained the air pump system, air conditioning, and evaporative emissions controls--not the prettiest stuff in the world to have under your hood, but street friendly nonetheless.
Keeping a close eye on the...
Keeping a close eye on the engine oil is important not only to make sure that the crankcase stays filled, but to inspect the oil for color and smell. For example, coolant entering the crankcase will usually cause the oil to appear milky. The LS1 engine is known to occasionally have this happen when equipped with an MLS-style head gasket, but these leak issues usually only occur when the block or cylinder head deck is not properly prepped. Fortunately, our machine shop and head manufacturer did good jobs with these respective surface finishes, and no such problems were experienced.
FIRE IT UP--WITH CARE
With any newly installed engine, there's bound to be one or two issues to resolve right off the bat--and they might surface before the engine is even fired. Care must be taken that any problem be identified and dealt with immediately, lest you risk damage to your engine--or yourself. So before you bump the starter motor, be sure to:
* Take one last look that oil, coolant, and other fluid levels are topped off.
* Turn on the ignition; look for any arced wires, and listen for anything suspicious.
* Cycle the fuel pump a few times to build pressure in the fuel rails; check for any leaks. Both sight and smell are key here. (If you've just installed an aftermarket fuel rail system, don't be surprised if some of your AN fittings need to be tightened a bit more.)
* Have a fire extinguisher and battery disconnect wrench close at hand--you can never be too safe!
The moments just before a new motor is first fired are possibly the most nerve-racking in any engine build; but if you've taken the time to do things right, chances are excellent that you'll be home free. With the above final items checked, turn the starter--so long as basic provisions like fuel injector size have been addressed in the PCM tune (we'll get to all that momentarily), the engine should start up and run immediately. Watch that oil pressure comes up within the first few seconds--this is absolutely essential. (If it doesn't, stop and find out what's wrong!)
Pulling out spark plugs can...
Pulling out spark plugs can be a relative pain--especially on a Fourth Gen F-car like ours--but it's a necessary part of making sure an engine is running healthy. It's important to remove and inspect the spark plugs after some miles have been accumulated on a new motor, as they can be an excellent indicator of engine health. For example, an overly black or sooty plug can indicate an overly rich condition or a problem with your ignition system. Also, abnormal plug deposits or discoloration can be indicative of contact with coolant and a head gasket problem.
With the motor running, don't just start driving around, as you're not quite in the clear yet. As the engine starts to warm up, continue to watch for fuel or other fluid leaks--metal and fluid changes that occur with rising temperature mean problems that don't show themselves immediately could quickly and without warning cover the garage floor with liquid. As soon as the coolant reaches full temperature (indicating that the thermostat has opened), turn the engine off and let it cool to the point where you can open the radiator cap. Top off the coolant as needed; this may need to be done a few times. Also during this initial engine run time, listen for anything mechanical that sounds strange, like lifters that haven't been able to pump themselves up; it never hurts to shut things down and wait a few moments for oil to dribble into where it needs to be rather than run a lifter dry and risk damaging it.
Our initial startup experience was relatively trouble-free, other than a mysteriously dropping coolant level, which turned out to be due to a bad radiator cap. No abnormal noises were heard emanating from under the hood, and we immediately noticed that our 383 exhibited a lopey idle that definitely did not sound stock. So much for a sleeper! We also took note that with our high-volume SLP oil pump circulating the lifeblood of the engine, plenty of oil pressure was at hand--always a good sign in a brand-new engine. Having passed these initial checks, all systems are go--we're ready to start driving and getting this engine broken in!
Your new stroker might be...
Your new stroker might be capable of 7,000 rpm or more, but don't even think about trying to achieve that during the first few miles of driving. Thanks to advents like rollerized valvetrains and improvements in engine oil formulations, engine break-in procedures are far less elaborate than in the past--but you'll still have to use some restraint and take it easy on the throttle for the first miles of driving.
THE BIG BREAK-IN
OK, so it runs--good work! But your big-cube engine isn't quite ready to impress your buddies on joy rides, much less hit the local drag strip--and we're not just talking about making sure the tune is dialed-in (more on that momentarily). Anyone who knows the least bit about automobiles has heard the shpiel that new engines need to be "broken in." Going through this procedure ensures optimum power output and long component life, but what exactly is going on here, and what's important to know for the Gen III?
During the first several hundred miles of operation, the metal parts of the engine "mate" to each other. While advances in technology mean that engine parts are manufactured to more exacting tolerances than ever before, the microscopic uniqueness of any one piece of metal that comes off of the assembly line or out of a machinist's cylinder honing machine continues to endure. Think of this mating like the last step in machining: all surfaces that contact one another "wear" or "finish" each other to the point they'll operate at for the rest of the life of the engine. We want this initial wear-in to occur, but if we try to get it to happen too fast, the engine parts will instead wear out prematurely.As far as GM small-block engines go, allowing flat-tappet lifters to properly mate with the camshaft lobes was a huge concern back in the day. This necessitated special lubricants, and also required the engine to be spun above a minimum rpm for the moments following initial start up. Happily, those days are ancient history, and thanks in part to this advance, no elaborate, "ceremonial" break-in is required for an LS1-based engine. But our beloved V-8s still have important parts like bearings--and most significantly, piston rings--that require a wear-in period to operate properly.
So, how to go about this? We spoke to Mark Chacon, Lunati's East Coast Regional Rep., about his thoughts on this issue. "As motors are breaking in, and in regards to piston ring seal, they want a constantly changing engine rpm environment. This is why city driving is generally the optimal condition for any motor break-in. The worst thing that you can do with a new engine is to put it together, fire it up, and then head down the interstate with the cruise control on. While a little bit of freeway driving is OK, certainly for the first 500 to 1,000 miles I would try to avoid long trips or periods where you're operating at a constant engine speed," says Chacon.
OK, so staying at any one engine speed is bad, but this isn't to say you can go take your new engine to six grand the first time out. On the contrary, restraint must be used to keep engine speeds and loads reasonably in check. "Don't go out there and just hammer through the gears all the time; you need to be a little more conservative about how you drive the vehicle. A varied range of rpm usage, combined with keeping it easy on the motor, allows the face on the ring to do a better job of seating to the cylinder wall," says Chacon.
The type of fluid used during break-in is also important. You may have heard that synthetics are "too good" to use during the first miles on a new engine, and this is true. The main reason for this is the piston rings, which as we have said need time to seat to the cylinder walls properly; if they don't, horsepower and efficiency will be left on the table thanks to reduced cylinder pressures. Mark Chacon elaborates: "The ring face must have ample time to break in to the cylinder wall finish, and running a conventional oil for the first 1,500 miles or so will aid this. Ring seal needs to be firmly established before synthetic is introduced into the motor, and one of the reasons the factory LS1 has such a heck of a time with ring seal to begin with, in my view, is that many come from the factory with synthetic oil in them. Once you put synthetic in, what you've got is what you've got, and the rings may never really wear to the cylinder walls. Of course, feel free to eventually switch to synthetic because of its better properties, but make sure the rings have seated fully first; short of using a cylinder leakdown tester, mileage accumulation is the only way to tell whether this has occurred."
As engine parts wear in, more small metal particles are being cast off into the engine oil than would usually be expected. Therefore, keeping the engine oil clean during the break-in period is essential. In furtherance of this, be sure to use a high quality, high capacity filter that can capture very fine particles. As to fluid change intervals, a good rule of thumb from Lunati is to drop the oil after 100 miles to get the initial bearing cast-off material out of the system. Then, change the oil after 500 miles, and again after 1,500 miles have accumulated, from which point forward you can follow manufacturer-recommended change intervals and swap to synthetic oil if desired. Stick to these simple driving and engine oil maintenance tips during the break-in period, and you will help your stroked LS1 live a long, happy life under your GM performance car's hood.
Royal Purple's Extreme Performance...
Royal Purple's Extreme Performance and Racing (XPR) 10W40 is a proven formulation for the ultimate in engine protection and horsepower. This lubricant uses the company's Synerlec additive technology along with other ingredients to reduce engine wear by up to a claimed 80 percent versus other racing oils. Also available in viscosities ranging from 0W10 all the way to 20W50, a quart of XPR can be had for a suggested $13.45.
OIL: YOUR ENGINE'S LIFEBLOOD
We've already discussed the importance of accelerated engine oil change intervals and the use of conventional oil during an engine's first miles. What we have not covered is the viscosity of engine oil to use, as well as the advantages of eventually swapping to a synthetic oil.
Oil viscosity--or more commonly, "weight"--is an important fluid characteristic that needs to match up with a particular engine's physical needs. In the interest of not getting too technical on this subject, let's just say that the controlling factor in oil viscosity selection is how the engine's bearing clearances have been established. Recall from the first installment of this build our sidebar on "The Lunati Friction Package," where we went through and explained the reasoning behind Lunati's bearing clearances being set somewhat greater than GM does from the factory: basically, Lunati engineers prefer higher viscosity oil because of its inherent protection in severe situations. Because of this, our 383 stroker will need oil a good bit thicker than the 5W-30 that GM recommends for the LS1. Lunati's Mark Chacon instructed us that at least a 10W40 should be used to ensure the minimum 10 psi per 1,000 rpm oil pressure, with a 20W50 or similar heavier weight oil optional as well.
That said, why swap to synthetic oil after break-in? The short answer is that it offers more protection via the likes of reduced friction, corrosion, and wear. But not all synthetics are created equal. Texas-based Royal Purple, Ltd. is one of the leading manufacturers of premier high-performance lubricants for both consumer and industrial applications. Unlike some other companies that manufacture engine oil, Royal Purple's resources and talents are not diluted by expenditure of time and money on other petroleum products like fuel, enabling the company to focus exclusively on developing lubricants that outperform other synthetic or mineral-based oils. We spoke to Royal Purple's Jared Martin on the advantages of synthetic oils in general, as well as those of the company's "XPR" line of oil that we've chosen for our 383 LS1.
"First, it may be good to clear up a common misconception about the origin of synthetic base oils," says Martin. "Despite the common thinking that they are completely man-made--evoking visions of a mad scientist creating a Frankenstein fluid out of exotic materials--the most widely used synthetic base oil in automotive applications is actually derived from crude oil, just like mineral base (conventional) oils. The huge difference is in how the two are refined. Synthetic base oils are completely broken down, stripped of virtually all impurities, and then are essentially pieced back together, hence their man-made or synthetic nomenclature."
"This costly refining process yields significantly greater performance than conventional oils in a number of ways," continues Martin. "Because synthetic base oils have a long-chain, uniform molecular structure, they have higher viscosity indices (VIs) as compared to mineral base oils. The higher the index, the less change in viscosity over a given temperature span. In addition, synthetic base oils naturally possess lower pour points due to their purity and molecular structure. The contaminants found in mineral base oils (wax, paraffin, silicone, etc.) are removed, thereby increasing resistance to the effects of heat, yielding far greater oxidation resistance. Also, the inconsistency in molecular size and shape of mineral base oils significantly reduces their shear stability; and synthetic base oils have a higher specific heat, meaning they carry and dissipate heat more efficiently."
"While synthetic base oils do provide performance benefits over mineral base oils, keep in mind that base oil is a mere starting point. Engine oils are typically made up of 15 percent to 25 percent additives, which are used to tweak performance. Because additives essentially define the performance of a finished product, it could be said that a well-formulated mineral-base oil may outperform a poorly-formulated synthetic. However, if equal or greater focus is placed on the additive formulation when used in a quality synthetic base oil, the lubricant can reach a whole new level. Such is the case with Royal Purple and our Synerlec additive technology. Synerlec amplifies many of the inherent benefits of the synthetic base oil, particularly film strength and oxidation resistance, both of which have been found to be multiple times that of even other synthetics of the same viscosity," says Martin.
For this project, Royal Purple recommended its Extreme Performance and Racing (XPR) line of engine oils, which is a new marketing twist on an existing and proven formulation. Previously referred to simply as the "Racing" line, Royal Purple has renamed this line of oils to better project the products' viability in high performance street applications. "This LS1 stroker build is an ideal candidate for such a product," says Jared Martin. "The XPR line differs from our other products primarily in that our Royal Purple SAE engine oils are API/ILSAC licensed for OEM warranty approval, and this licensing process limits us on what we can do with certain additives to tweak performance. In contrast, the XPR line is designed specifically for customers that have no warranty--or have already voided it 100 other ways--and are looking for maximum performance! While it's true that thanks to our Synerlec technology (which is not API/ILSAC regulated) our SAE oils already outperform most other "racing" oils, the XPR line redefines the class. I usually recommend stepping up to the XPR line when a customer has either installed a power adder, stepped up the boost on a factory blower or turbo car, or has made internal engine modifications. Such is exactly the case with GMHTP's project LS1 stroker."
When Jared first mentioned the fact that the XPR line of oils is not approved for use in new vehicles under warranty (you won't find the API approval starburst on an XPR bottle), I was a bit skeptical of its suitability for a street driven vehicle. However, I was assured that what this approval process all comes down to is an emissions issue, and not even a proven one at that. "The main two elements the API is concerned with are zinc and phosphorous, which are used to form the compound zinc dialkyl dithio phosphate, commonly referred to as ZDDP," says Martin. "These have been the cornerstone of anti-wear technology since additives began being used in lubricants. What the API and EPA are concerned with is the potential effect of phosphorous on emission control devices like oxygen sensors and catalytic converters. It is speculated that higher degrees of phosphorous will lead to an early demise of these devices, though I have yet to see conclusive evidence of this. So rather than placing the burden on the manufacturers of these emission control devices to better withstand the effects of these elements, the regulatory agencies instead choose to reduce the upper limitation of these elements in engine oil. While I'm not at liberty to get too deep into what separates the Royal Purple SAE and XPR oils, I can say that due to our Synerlec technology it has very little to do with the ZDDP issue. Rest assured that foregoing any API licensing with our XPR line gives us the ability to design a lubricant from the ground up, enabling us to make a better product."
While engine mileage was insufficient to enable us to install this oil prior to our dyno and track testing, we'll be doing so at the next oil change--endowing our 383 Gen III with long life and more power.
Maintaining all fluid levels...
Maintaining all fluid levels is an essential task, as you especially don't want to run your brand-new engine low on coolant and possibly overheat it. Also, air bubbles will take a bit of time to find their way out, requiring at least a couple of top-offs. This liquid is also a window to your engine's health: coolant discoloration could be a sign of a head gasket problem (such as combustion gases entering water passages). Also, a continuing drop in fluid level here or in the surge tank could mean that coolant is escaping through a leak in the system. This leak could be the result of something as innocent as a damaged radiator cap (as in our case--whew!), or as sinister as a poorly sealing head gasket dumping coolant into the oil system.
TUNE AND TEST
But wait; we just got ahead of ourselves. The observant reader might realize that we've glossed over a critical area--one that must be addressed whenever an engine is anything more than mildly modded. He or she would probably ask, "Hold on... is my new stroker motor really going to run with a stock computer?" The answer, roughly, is no. With a heavily modified engine like this one--more cubes, big-lift cam, high-flow heads, etc.--stock or near-stock fuel and ignition maps simply won't cut it. Though the engine will likely start and run on a factory tune (assuming stock fuel injectors are being used), parameters would likely be so far off that even if the car were able to be driven, it would probably be a bad idea even for break-in purposes. Therefore, the home engine installer will need to make a choice with regard to tuning. The first option is to completely learn a PCM tuning program and construct all engine maps from the ground up--a daunting task. Another is to get a local shop to perform a full custom tune, which is viable, provided you have a trustworthy and affordable tuner in the area. The final route is to take the middle road.
Middle road, you say? This third option, which is the one we have chosen to pursue (at least for the time being), involves having the PCM flashed with a customized mail-order calibration. Though often this will not result in a dead-on tune, the enthusiast can use what limited tuning abilities he or she might have to dial it in using commercially available scanning and tuning software. See the sidebar on the Thunder Racing tuning we chose for this build, and follow along below as we take steps to evaluate the suitability of this calibration, as well as make fine adjustments to match it more closely to our vehicle. Although we won't purport to supply all-encompassing analysis and instruction on how to tune your vehicle (as PCM adjustments are, by and large, beyond the scope of this story), we'll fill you in on a few tips and tricks to help you evaluate whether you can handle such a task yourself or would rather leave it completely to the pros.
Application-specific PCM tuning...
Application-specific PCM tuning really can be had at an affordable price, and getting a hold of it is a simple matter of packing up your PCM and shipping it to Thunder Racing's Baton Rouge headquarters. Based on the information you provide on the company's Custom Tune Worksheet, which contains detailed questions to answer about your vehicle's modifications, the knowledgeable techs will devise and flash a full custom tune into your PCM, and send it back your way. It's that simple!
THUNDER RACING: PUTTING YOU ON THE MAP
Louisiana-based Thunder Racing is one of the country's larger retailers of aftermarket parts for late model domestic performance vehicles. These folks carry virtually any part from any manufacturer that you'd want for your late-model GM ride, including most of what we've used in this engine build. Thunder obviously knows its customers like to buy go-fast goodies, and so its computer tuning service is the perfect complement to the company's extensive retail product line.
Available for virtually any 1994-later GM V8-powered ride, Thunder sells basic tuning for mild mods, which includes adjustments to the rev limiter, shift points, speedometer recalibration, torque management deletion, and performance fuel and timing curves, among other things. This service can be had for $150. If your ride steps beyond what this basic tuning service can address, don't fret: Thunder offers a custom tuning service for vehicles with more serious hop-ups. Designed for heavily-modded engines with goodies like an aftermarket cam and heads, the custom tuning service (which goes for $450) includes all of the features of the basic service, but adds highly customized spark and fuel tables tailored to a customer's specific combination of parts-optimizing power and drivability. This is the service we've selected for this project.
Though the company's personnel are extremely experienced in their tuning capabilities, having tuned many vehicles on its in-house dynamometer, Thunder's Geoff Skinner had some honest commentary for us regarding not only his capabilities, but the capabilities of mail order tuning in general. "Some mail-order tuners claim to be able to wave a magic wand and send off a perfect tune to a customer for every possible engine combination," says Skinner. "While we're able to get at least 90 percent close to an ideal tune for engines with known parts combos that we've also built in-house in the past, the huge variety of aftermarket parts available on the market means that being able to get a completely perfect tune in every single scenario for everyone is simply not possible. The simple fact is that every car is different, even two cars that have the exact same aftermarket parts installed on them. So a good portion of the time, our custom tuning service will not be an end-all solution, but we can at the very least get you in the ballpark of your ideal PCM calibration."
That said, would the PCM tune Thunder provided for our 383 LS1 prove adequate? You'll see in the main text how pleasantly surprised we were at how well our vehicle drove and performed--not wanting to leave well enough alone, however, we decided to try and evaluate and further dial in this tune. I'll also show you some of the things I learned in playing with our EFILive tuning software (unlike some other GMHTP staffers, this author is not an expert tuner), as well as pointers from Thunder Racing and buddies more knowledgeable than I. See the main text for this information.
Innovate Motorsports sells...
Innovate Motorsports sells its LC-1 Wideband Controller kit under PN 3769 ($199.99). This will get you everything you see here: the controller, detailed instructions, software, a Bosch oxygen sensor, weld-in bung and plug, and all necessary wiring and cables for a trouble-free, permanent hookup that stays on board and interfaces with your laptop computer as needed. FYI, other wideband systems are available that can be swapped between vehicles, or that include AFR gauges to mount inside the cockpit.
OXYGEN SENSORS: GOIN' WIDE
PCM tuning is not a task for the faint of heart, and that's why there are so many shops available around the country who can help you out. But when trying to do at least some of it yourself, the single most important tool you can add to your arsenal when dialing in the computer calibration on your newly stroked ride (other than the tuning software itself) is a wideband oxygen sensor. By being able to monitor the engine's air-fuel ratio in real time, tuning status and changes can be accurately evaluated. Now, it's true that all vehicles sold today come with oxygen sensors already on board--but almost without exception, they're "narrow band" units that can only accurately read AFRs near stoichiometric 14.7:1. Full throttle AFRs need to be significantly richer than this for optimum power and safety, and only a wideband can accurately monitor these. From helping verify that a typical enthusiast is in the ballpark with a mail order tune, to assisting more experienced persons in customizing fuel and spark maps from the ground up, tuning simply can't properly be done without a wideband.
For the novice and expert alike, the absolute best way to evaluate and adjust PCM parameters is to use a chassis dynamometer to put the vehicle through its paces. As fate would have it, most of us don't have dynos in our garages; so unfortunately money will most often need to be spent renting one out. And while it's true that many dyno shops already have wideband O2s hooked into their equipment, chances are you'll want to use a scan tool to acquire some information via street logging before spending dough on a per-pull dyno roller romp.
Follow along as we install an Innovate Motorsports LC-1 wideband on our project Firebird. The LC-1 can be used both as a standalone product--with real-time readouts being displayed by the provided LogWorks software--or in conjunction with tuning software such as EFILive. We'll be hooking up for the latter option, but take note that even when so wired (which configuration differs only slightly from standard wiring), the unit's multiple outputs mean that the Innovate LC-1 can still be used as a standalone product simultaneously--a convenient feature.
TUNING: DIALIN' IN
We'll admit it: we were a bit apprehensive about how well someone could tune a vehicle from well over 1,000 miles away without having ever even seen it--particularly a heavily modded car such as ours. After weeks upon weeks of engine assembly and installation, the success of the entire project still hinged upon proper PCM calibration. A poorly tuned engine yields a poorly-running and poorly-performing vehicle--and I'll be the first to admit, even though tuning was coming from folks as reputable as those at Thunder Racing, I was a little worried.
But I'm happy to report that, all things considered, Thunder did a great job on our tune. It was a pleasure to find how well our Trans Am ran and drove; throttle response was excellent, no noticeable burbles were present in the powerband, and fuel mileage was decent (though of course off from stock a couple mpg thanks to our big cubes). Before we knew it, we were cruising local car shows and turning heads, unable to resist the urge to open our QTP electric cutout and let onlookers better hear the lopey idle provided by our Lunati cam and the deep rumble of our 383.
Very few drivability issues emerged during our first few miles on the road, and we'll hit the highlights of them and how they were dealt with in the photo captions. Along with talking to Thunder Racing for help and insight, I also had a GMHTP contributor experienced with EFILive tuning have a look at the maps; based upon the readings seen using EFILive's Scan Tool and our Innovate LC-1 wideband, these folks were able to point me in the right direction with respect to some minor tune adjustments. Check out the photo captions for more information. (And note in the accompanying screenshots we're only showing a portion of each screen for clarity.)
COST: THE BIG PERSPECTIVE
Alright--before getting to any results, let's talk money. Remember that we've gone through the trouble of building our own 383 Gen III from the ground up with the dual purposes of saving some cash and being able to say the phrase, "I did it all myself." The inestimable satisfaction of a job well done aside, was it really all worth the wallet hit? That is, what did we actually end up spending dollar-wise, and how does this weigh against buying a comparative complete engine and having the work done by a professional shop?
As much as we'd like to be able to give an absolute dollar value in savings, this isn't as easy as it might first seem. In fact, it's not possible to draw direct apples-to-apples comparisons for many reasons, a few of which are as follows. First, nobody sells a complete engine using the same parts that we've incorporated into this build, so an actual assessment of savings simply in assembly costs would be an exercise in pure speculation. Second, it's highly unlikely that a typical shop will install an engine that someone else has partially or completely built, meaning any separation of engine build costs from engine installation labor costs is artificial at best. Not to mention, all of the prices we've quoted in this build series are MSRP, meaning a lot of the parts we've used can probably be had for substantially less money from large retail suppliers. Perhaps worst of all, the total package we've brought together entails many components, some of which people would consider parts of a complete crate engine, others a part of a long-block, and some neither--people's definitions of these terms simply differ.
If you shop around, you'll find that you can buy a stroked LS1 for under $8,000 from some places--but this price generally doesn't even include the likes of an intake manifold, engine covers, throttle body--and often not even rocker arms. Considering that all of these items are included in what we've put together here, it means that the $8,000 number is pretty low. A more realistic assessment of the average comparably equipped engine would, by our count, probably be close to $12,000 (see "25 Hot EFI Crate Motors," April 2006). And then you're not even paying for installation, which as we've already mentioned is a complicating factor; though you might get fortunate and be able to have this done for a bit over $1,000 at a local shop, even this price would most likely only be for a very basic direct swap.
In our research, we did find a few sources that offered the kind of complete engine build and installation we've performed here. In doing some local shopping around in particular, the lowest overall price we found for a similar 383-inch engine with a good set of cylinder heads, cam, and big intake--installed and all--was well over $11,000.00. Look to some of the big-name, more-nationally known folks, and you're probably looking at a minimum of $15,000.00 for an installed stroker engine package--and that's likely with only ported stock (not aftermarket) heads and intake.
So since true comparisons are so difficult, let's do a rundown part-by-part to see where we're at with our particular build. We'll show what we've bought, whether it was a necessity for the build (or was more of a "luxury" option), and give some possible alternatives along the way for the truly budget-minded. See our prior "My First Stroker" installments for detailed part numbers and specifications on all of these items.
Let's first add up the parts needed to make the typical "long-block" you'd be able to find from your usual engine builder. Though long-blocks are, again, sold in differing configurations, we'll go with your most typical: fully complete engine internals and valvetrain, oil pump included, but no engine covers included:
|LONG-BLOCK PARTS: |
|Block (freshen existing)||$277.20 |
|Rotating assembly (Lunati)||$3,800.00 |
|Main studs (ARP)||$240.02 |
|Side main bolts (ARP)||$29.50 |
|Cylinder heads (ETP)||$2,399.95 |
|Head studs (ARP)||$372.83 |
|Head gaskets (Cometic)||$153.20 |
|Camshaft (Lunati)||$310.00 |
|Lifters (Lunati)||$410.00 |
|Pushrods (Manley)||$140.00 |
|Rocker Arms (Jesel)||$1,525.00 |
|Oil Pump / Timing Chain (SLP)||$339.95 |
|TOTAL LONG-BLOCK PARTS||$9,997.65 |
As far as we can tell, this figure ends up being toward the higher end of the price spectrum for a comparatively equipped long-block--so at first glance, it may look as if our efforts were fruitless. But take a closer look at what we've done here, and we think you'll appreciate that there really are savings. In Lunati, we've got one of the strongest rotating assemblies on the market. Sitting atop our block are a sweet set of 11-degree aftermarket heads, whereas many engine builders use ported GM units. We've got the same shaft rocker arm system proven at endurance races throughout the world. And we have bulletproof main and head fasteners from ARP, where others often use OEM replacement stuff. If one were to make a few phone calls and specify these or similar top-tier options with some engine builders, we can almost guarantee that you'd be looking at substantially more than $10,000 for any given long-block. But if you're not looking for the kind of bulletproof setup we've ended up with, certainly as much as a few thousand bucks could be cut off of our dollar figure--just be aware that this will almost certainly come along with an incremental decrease in engine reliability.
Now, to put together a long-block such as ours, you'll of course need some of the specialized tools you've seen as this build progressed, and this cost can't be ignored. But keep in mind that nearly all of these tools can be reused in future engine builds or similar undertakings, so it's questionable whether they should really be considered part of the overall cost of the engine. Also, don't forget that many of them can likely be borrowed from local machine shops or your auto-enthusiast buds. But even assuming your social popularity is poor and you don't have any such contacts--and that you've already got yourself an array of sockets and a couple of good torque wrenches--here are all the tools you'll definitely need to buy to assemble an LS1 long-block (all items are from Powerhouse except as noted):
|LONG-BLOCK TOOL |
|Crank Turning Socket ||$44.95 |
|Dial Caliper ||$44.95 |
|Dial Bore Gauge ||$99.00 |
|Piston Ring Filing Tool ||$65.00 |
|Piston Ring Squaring Tool||$24.00 |
|Piston Ring Compressor||$28.00 |
|Connecting Rod Vise||$89.95 |
|Rod Bolt Stretch Gauge||$119.95 |
|Degree Wheel||$16.00 |
|Head Bolt Clean-Out Tap (ARP)||$51.34 |
|TOTAL LONG-BLOCK TOOLS||$583.14 |
This brings our total long-block "assembly" cost to just over $10,580 (with a few dollars left out for miscellaneous assembly lubricants, sealants and solvents--items that cost less than $50 total and that we'll add into final figure below). And remember, we'd be shocked if you didn't reuse at least some of these tools on future engine builds or other projects around the garage.Actually spec'ing out how much we've spent in terms of a "crate engine" is far more difficult. Generally, this term defines a complete, turnkey engine that's meant to be dropped into an older GM ride that never had an LS1--or perhaps not even EFI. At a minimum, a crate motor most often includes additional parts like an intake manifold, throttle body, engine covers, and a harmonic damper. As applied to a mill destined for installation under the hood of an F-body or Vette, buying an engine so equipped saves the trouble of reinstalling many of these items--but it also means stuff like your existing engine covers or perhaps even the big-bore intake you installed last year might be duplicated. Unless you can auction off your used parts for decent coin, this translates to a waste of money. Adding more confusion into the mix, other times the crate engine term is applied to engines that include what might otherwise be called engine accessories, like ignition coils, fuel rails, and a water pump.
Since our project focused on a stroker build for your typical already-LS1-equipped ride, we're not going to add this complexity into the equation; we'll only include below what we ended up actually buying and leave it up to the reader to cross-reference these items with what might be needed (or desired) for a stroker swap into his or her own ride. That said, let's add up the parts we considered "necessary" for our particular build (this mostly means those parts that it would have been a bad idea to reuse from stock in terms of reliability), as well as those we didn't technically need, but are "nice to have" and will add to our performance potential nonetheless.
|"NECESSARY" STROKER PARTS: |
|Harmonic Balancer (SLP)||$236.85 |
|Gaskets (2) - Water Pump (GM)||$9.68 |
|Gaskets (2) - Valve Cover (GM)||$36.90 |
|Gasket - Rear Cover (GM)||$21.61 |
|Gasket - Front Cover (GM)||$21.61 |
|Gasket - Oil Pan (GM)||$33.91 |
|Gaskets (4) - Air Bleed Pipe (GM)||$19.80 |
|Grommets - Knock Sensors (GM)||$3.41 |
|Crankshaft Seal, Front Cover (GM)||$21.06 |
|Crankshaft Seal, Rear Cover (GM)||$18.63 |
|Engine Block Rear Oil Galley Plug (GM)||$5.92 |
|Valve Cover Breather (Speed Inc.)||$44.95 |
|TOTAL "NECESSARY" PARTS:||$474.33 |
|"NICE TO HAVE" STROKER PARTS: |
|90mm Intake (Top shell only - FAST)||$549.95 |
|90mm Throttle Body (Holley)||$475.00 |
|90mm Throttle Body Seal (FAST)||$9.27 |
|Ignition Coils (MSD)||$578.60 |
|Spark Plug Wires (MSD)||$59.30 |
|Thermostat, 160-degree (SLP)||$56.60 |
|High-Flow Fuel Rails (Speed Inc.)||$139.99 |
|Fuel Rail Installation Kit (Speed Inc.)||$99.99 |
|TOTAL "NICE TO HAVE" PARTS:||$1,968.70 |
A few quick notes on the above: recall that it's best to borrow the alignment tools for the front and rear engine covers and oil pan since they're so expensive (in fact, they actually aren't absolutely necessary, but they're still a very good idea). Also, Wheel to Wheel Powertrain will install new crank seals in your existing front and rear cover for $139, so figure this in when pondering over gasket prices and install tools.
This brings us to the best estimate of our total stroker "crate motor" price, including all necessary and nice to have parts: $13,023 and some change. Adding in our few primarily cosmetic add-ons gives a modest increase over this:
|"LUXURY" STROKER PARTS: |
|Cam Retainer Bolts (ARP)||$8.20 |
|Rear Cover Bolts - Stainless (ARP)||$27.60 |
|Front Cover Bolts - Stainless (ARP)||$29.27 |
|Engine Mount Bolts - Stainless (ARP)||$22.50 |
|Coil Bracket Bolts - Stainless (ARP)||$68.56 |
|Water Pump Bolts - Stainless (ARP)||$36.25 |
|TOTAL "LUXURY" PARTS:||$192.38 |
Finally, to give a more realistic showing of how much it'll really cost to swap a stroker into your ride, we'll need to include miscellaneous stuff like fluids (coolant, oil, etc.), thread sealer, spark plugs, belts, clutch and flywheel bolts, a pilot bearing, and other miscellaneous last-minute stuff you may or may not need--and may already have lying around. Rather than listing every last one of these little items, we'll just say we spent in the neighborhood of $200 on them. Throwing another $450.00 or so on top of this for our mail-order tuning and $199.99 for our wideband, we'll even add in the $700 or so for a scanning and tuning tool like EFILive (which we had already--you may or may not; and don't forget such an item can be used to tune multiple vehicles).
So our absolute grand total--soup to nuts--comes to $14,765, give or take a few dollars. It's a good chunk of change; but remember, this price is for an installed, tuned (and further custom tuneable) engine package that is all-inclusive of some of the strongest and highest-quality components you can buy, and reflects the additional cost of more than a few parts that weren't actually necessary for the build. Recalling the prices we researched and reported above for an installed engine package, we're within the same price range, even if it's toward the upper end of it.
All that said, a couple of conclusions should be clear in the mind of the reader. First, the vast majority of engine builders and installers aren't ripping people off by any stretch of the imagination. It's a competitive market, and there are a lot of good deals out there when it comes to stroked LS1 engines, be it a long-block or a fully installed package; to make power costs money, and when you come down to it, there's no way around it. But more importantly, we hope we've shown that the avid enthusiast who likes to get his or her hands greasy can build an engine in the garage--and that by performing such an assembly at home and doing a lot of careful research, he or she can get some better-quality and higher-power-potential parts under the hood for an equivalent or lower price than the professionals offer their services for.
THE REAL BOTTOM LINE: PERFORMANCE!
OK great, we've just built our own engine, and we did it while saving at least a little cash and simultaneously building in strength--and hopefully, horsepower--we may not have been able to afford otherwise. So what kind of performance results did we end up with? After a full break-in, we were ready to find out!First off, know that we're not turning the nitrous on just yet--we need to evaluate whether we have adequate fueling and what kind of tune changes we'll need, if any, for when the spray is engaged. (Ideally, we'd like to retard spark automatically when the nitrous is flowing rather than having to run a "de-tuned" calibration at all times. We hope to be installing products for this purpose in upcoming issues.)
This fact noted, check out the accompanying dyno charts for how our impressive torque curves and power numbers compare to our totals from our internally-stock LS1 engine, using both our Thunder Racing tune as well as our slightly-modified calibration. You'll note how power begins to fall off after peaking at around 6,200 rpm--higher than our stock engine's 5,500 peak, to be sure, but still a bit lower than might be expected. Let's keep in mind, however, that this 383 LS1 is a "small bore/long stroke" engine, with the 4-inch crank throw being large compared to the 3.903-inch bore. An engine with such characteristics often results in a downward "shift" in the powerband versus an equivalent displacement engine with a shorter stroke (and bigger bore). Also, we likely would have experienced an even higher power peak at a greater rpm had we gone with 225cc ETP heads in lieu of the 215cc units--but torque in the midrange may have suffered.
So you can see that we've gained nearly 100 hp and 75 lb-ft at the tires over our internally-stock LS1's dyno reading from immediately prior to the stroker installation. Admittedly, our 346-inch LS1's tune was running retarded timing to accommodate our nitrous shot, so horsepower and torque numbers would have been higher had we been using closer spark advance to what we are currently (18.5 degrees then versus 26.5 now). Still, it's probably safe to say that we've picked up around 100 hp at the engine, bringing crank totals to the neighborhood of 535 hp and 523 lb-ft SAE.
Also intriguing is the fact that although we performed slight adjustments to fuel and timing over Thunder's maps, torque and hp remained nearly identical. Apparently, the nearly 1 point leaner AFR we achieved was offset by the 1 to 1.5 degrees of timing we took out of the map. Though we're still at a slightly rich, mid-to-high 12s on the AFR with this tune, my lack of tuning experience told me to keep things as-is rather than risk leaning out further or adding a bit of spark advance only to achieve knock. I'll likely wait for a professional tuner to get his hands on the car before attempting to unlock any more horses (my guess: possibly as much as 20 rwhp is still on the table), or perhaps I'll brave the PE table a bit more myself on the next trip to the dyno.
As to strip testing, we didn't have a magazine-only track session available between the time of engine completion and the deadline for this story to go to print. I considered it an injustice, however, the keep readers waiting through this entire motor build series, only to end up without a single drag strip slip (as most of our readers are, admittedly, drag racers). This noble cause in mind, I braved a late August open test and tune night at Englishtown, New Jersey. Here, I was greeted by hundreds of racers (many of whom managed to spill fluids all over the racing surface and put a hold on racing for what seemed like hours at a time) and a grand total of three (3) strip passes. Despite my years of relatively successful racing of stick-shift GMs, somehow two of these runs resulted in my missing Third gear. On the one full run I did achieve, I was still a good bit off in the driving department, with a lackluster start and some of the slowest granny-shifts I have ever performed (images of Rick Jensen saying, "You're an embarrassment to GM High-Tech Performance," raced through my head). Never one to shroud his failures, I'll quote you the timeslip value anyway: 12.55 at 115.5, with a 2.15 60-ft.
Since I've gone through the trouble of giving you a drag result, do me one favor: please don't consider this a true showing of this car's potential by any measure. The same excuse has been used time and time again by pretty much everyone who has ever traversed the quarter-mile, but it's never been so true as it is here--with the right driving and decent weather, 11s are almost certain to be had as-is with this combination (or damn close to it). With the right gearing and tires, perhaps low 11s or even 10s... but notwithstanding all the extra gas, photo equipment, and Pirelli street radials adorning the car that August night, 12.55 is still the best ever ET for this vehicle--including the stock engine on laughing gas. Rest assured, we'll update you as improved drag strip times become available.
A closeup view of the controller...
A closeup view of the controller box shows some notable details. On one end is the plug for the oxygen sensor to attach to (left). Coming off the opposite end are two thin serial in/out cables, which allow programming and monitoring of the system, as well as a thicker cable, which is shielded and contains the batch of wires that need to be hooked primarily to the vehicle. As you can see, the unit is sealed and weatherproof, so it can be mounted either inside or outside of the cockpit (zip ties are the preferred mounting method).
The ends of the controller's...
The ends of the controller's cables look as follows. In the upper right of the photo we see the serial in/out ports, to which connect either the provided 2.5mm male terminal plug and/or the provided 2.5mm stereo to DB-9 cable (the other end of which hooks to your laptop computer). As to the seven wires emerging from the thick shielded cable, they'll be tapped in as follows: red to an ignition-switched 12V source; blue (the sensor heater ground) will go to the chassis; black is the calibration wire that we'll be wiring to ground through a momentary switch and LED; white and green are system and analog grounds and will wire to our EFILive FlashScan cable; and yellow is the analog output and will also wire to our EFILive cable, providing EFILive with a voltage signal that will be translated into AFR. (The brown wire is a second analog output and won't be used in this application.)
Before wiring anything, let's...
Before wiring anything, let's install the hard parts. Innovate insists that the system's oxygen sensor be located prior to the catalytic converter on vehicles so equipped, as the company says the gas-altering nature of catalysts can alter the air-fuel ratio reading seen by the sensor. Not wanting to drill our headers, we opted to go right into our Dynatech cat housing with the sensor, and made the appropriate size hole using a drill press.
After ensuring the hole drilled...
After ensuring the hole drilled is of adequate diameter (lay the bung over the hole and make sure no exhaust pipe metal is visible when looking through it), it's time to weld. Insert an appropriately sized bolt while doing this so that the bung stays centered over the hole; absolutely do not weld with the O2 installed into the bung! Tack the bung in place first, then check that the actual sensor screws in; verify and continue.
With the bung welded in place,...
With the bung welded in place, the metal is allowed to cool before screwing the sensor in. Here we're looking into the inlet of the cat, which on this vehicle bolts directly to the header collector. As you can see, the sensor is now optimally placed to read the exhaust gas mixture just before it flows through the ceramic interior of the catalytic converter. Satisfied with our sensor placement and installation, the cat is then bolted in place in the exhaust system.
The LC-1 controller box is...
The LC-1 controller box is strapped securely to the underside of the transmission crossmember. On a Fourth Gen F-body, we found that it'd be easiest to interface with the vehicle's electrical system--and provide convenient hookups for a laptop--if the unit's cables were run directly into the vehicle's interior. The cables are so routed through a hole in the shifter boot, and are run carefully along transmission on their way so that they don't hit the spinning driveshaft or rub against anything that gets too hot.
Now it's a simple matter of...
Now it's a simple matter of plugging the wideband sensor into the LC-1 box, and the install underneath the vehicle is complete. Note that one must orient the sensor's placement about the exhaust pipe such that it falls between the 10 and 2 o'clock positions (to protect it from condensation that can form in the exhaust); happily, our cat was clock-able to allow this.
Inside the car, it's time...
Inside the car, it's time to get the LC-1 wires we've poked up through the shifter boot hooked up. A pre-existing spaghetti mess of electrical wires under the console works our nitrous system and electric exhaust cutout--we tap into these wires and grounds as needed for the aforementioned volt sources. You can also see we've got the LC-1's green and white wires (combining into black) as well as its yellow wire connected to an EFILive-provided orange screw terminal, which will snap into EFILive's FlashScan interface cable. (We're glossing over some details here, but Innovate has a helpful tutorial on the company web site about wiring to EFILive.)
The aforementioned orange...
The aforementioned orange screw terminal pops into our EFILive FlashScan V1 Interface Cable "black box", which has built-in analog to digital converters and will provide interpreted voltage signals to the EFILive scan tool software. We'll note that when the LC-1 box is first powered, it'll need to calibrate the sensor's heater controller, as well as perform a "free air" calibration. These two operations will give the LC-1 information on how to properly warm up the sensor as well as tell it the oxygen content in the atmosphere, giving a baseline to reference to. It's important that every wire be hooked up before this calibration, including both plugging this terminal in here as well as connecting the FlashScan cable to the OBDII port under the vehicle's dash.
To begin the calibration process,...
To begin the calibration process, the oxygen sensor must be unplugged from the LC-1 box underneath the car, powered for a few seconds, then turned off--this will reset the system. Plug the sensor back into the LC-1 box, and turn the ignition back on, at which time the LED you've wired in will flash in various ways for a few minutes while it performs these calibrations. Free air calibrations should be performed periodically (normally once a year), and rather than getting under the car and unplugging the sensor, you'll just need to press the momentary button I've got my hand on here--the heater calibration (which necessitates unplugging the actual sensor) need only be done once.
With the provided serial cable...
With the provided serial cable connected temporarily from the laptop to the serial out port of the LC-1, Innovate's provided LM Programmer software is used to program the LC-1's analog output with the correct voltage-versus-AFR curve to work with EFILive. Again, this information is provided in Innovate's tutorials. We'll also note that the LM Programmer software can be used for other functions, like setting the sensitivity of the analog output voltage. Because the LC-1's wideband sensor is so accurate, it can recognize individual pockets of exhaust gas as the cylinders pulse, and depending on the refresh rate of the data you are logging, this can cause the AFR reading to fluctuate somewhat artificially. It might be necessary to program the LC-1 such that the output voltage is averaged--for example, over the prior 0.3 seconds.
CONCLUSIONWith 383 super-reliable inches now under the hood of our Trans Am, the future is bright for this project car. Mods like a lower-ratio axle assembly, significant chassis bolt-ons, stickier rubber, and the like are all in the planning stages. But for the moment, it truly is one helluva stock-suspended, stroked F-bod, as the extra cubes have definitely forever transformed this Firebird for the better. Without a doubt, it drives and sounds like a totally new car.
That said, was the engine swap really all worth it? When we first began, we came out and stated that we wanted to "halve the cash" by building a stroked LS1 ourselves. Sadly, this statement simply didn't pan out. But as stated earlier, we were able to build in reliability and power potential we couldn't well have shelled out for otherwise; heck, this sucker isn't going to come apart unless the block itself gives up, and we will be throwing some nitrous at it presently to prove the point. Had we selected some real bargain-basement parts for the build, perhaps we could have met our goal as initially stated--but for a daily street driver that we plan on having see a bunch of recreational drag and road racing, that simply wouldn't have made any sense.
But we're forgetting to factor in the other half of the equation here: the satisfaction of a job well done. Like so many things in life, it's priceless. How many LS1 owners do you know can actually attest to building their car's motor themselves? Not many. Hopefully, that number will grow as the vehicles these engines came in become more affordable and owners are less afraid to tear into their hard-earned rides with their own two hands. I think we've shown--without a doubt--that to undertake and complete a full-on motor build such as this is within reach for a mechanically skilled, patient do-it-yourselfer. Having done it myself, I can tell you that the pride I now take in this car has gone up several notches, and nobody can put a price tag on that.
So I suppose the moral of the story should be this: if you're looking to bump up the cubes on your Corvette, F-car, or other Gen III-equipped GM, shop around. Based on your intended use, carefully weigh whether buying your own parts and bolting together your own motor will be worth your time and effort, as there are admittedly some decent deals on assembled and installed engines out there. But I can tell you this: I learned a heck of a lot of information about the LS1 during this build, and despite a few setbacks and delays along the way, enjoyed virtually the entire process. Had I let someone else turn the wrenches on my stroker, there's no way I could possibly have gotten as much out of it--and feel as much satisfaction as I do now rolling in my irreplaceable, 383ci WS-6 Trans Am.
With calibration complete,...
With calibration complete, the wideband is just about ready to start providing AFR readings to the EFILive Scan Tool software installed on our laptop. As you can see, not much has been added to the standard setup one would use while scanning or tuning with EFILive--just an extra orange plug sticking into the FlashScan interface cable.
EFILive's Scan Tool software...
EFILive's Scan Tool software comes ready to read an Innovate LC-1, and getting at the signal coming into the FlashScan V1 Interface Cable is as simple as selecting the "AFR_LC11" PID. With this parameter selected, we can incorporate the LC-1's readout into our EFILive dashboard. EFILive has excellent tutorials showing how to do this, and it's very straightforward.
With the LC-1 signal now a...
With the LC-1 signal now a part of our dashboard, the AFR reading seen by Innovate's wideband (shown here as the 4th parameter down, in light blue) can be viewed and logged simultaneously with any engine parameter--including rpm, MAP, knock retard, and so on--giving us very telling information about engine operation and helping immensely in diagnosing and changing PCM tuning. Pretty sweet!
Though the Trans Am started...
Though the Trans Am started and idled flawlessly the majority of the time, one slight hiccup we noticed was that when the A/C was switched on, the idle speed would drop slightly, causing a little more shake to the engine and tranny than we'd like. Fixing this was a simple matter of opening up the EFILive tuning tool and adjusting the "Desired Idle Speeds" table, which were increased by 75 rpm for the "In-Gear A/C On" column (the "In PN" columns only affect an A4 vehicle, hence the zeros here). No more annoying shake, though some is always present in a cammed motor of course.
In logging using EFILive's...
In logging using EFILive's scan tool, we noted that the long term fuel trims were a little excessive. Some amount of trimming is normal while in closed-loop mode; the PCM is constantly monitoring the air-fuel mixture using the onboard narrowband O2s, and automatically adjusting fuel injector opening times in order to achieve near a stoichiometric 14.7:1 AFR. Though several tables work together to mathematically come up with the command to send to the fuel injectors, one of the main ones is the "Injector Flow Rate" table. An inspection here and running of some numbers revealed slight differences between the table values and our actual fuel injector specifications (which flow 630 cc/hr at 43.5 psi), so numbers in the table were fine-tuned accordingly.
Another table that has a substantial...
Another table that has a substantial effect on the operation of the fuel injectors is the "Injector Pulse Width Voltage Adjust" table. Considered a more advanced table that won't often need to be messed with while doing basic tuning, a look at this can tell whether your fuel injectors are getting too big of a "boost" as alternator voltage increases, possibly resulting in commanding a too-rich condition--and resulting in large fuel trimming.
In terms of full-throttle...
In terms of full-throttle operation, our Innovate wideband indicated AFR's richer than we'd like to see. While the Injector Flow Rate table has an influence here as well, the primary table that controls fueling of this type is known as the "PE Modifier Based on RPM" table. Crunching the numbers, we noted that this table was currently commanding a full-throttle AFR in the neighborhood of 12.1 to 1. We swapped the values out across the board to command a more horsepower-friendly 12.8 to 1 (= 14.7 x 0.87, which is the value we placed in the table cells).
The final "major" change made...
The final "major" change made to our tune was with regard to ignition timing. EFILive's Scan Tool indicated up to a full 28 degrees of spark advance being utilized, but in a conservative decision to try and avoid any chance of detonation as we leaned out the AFR, we opted to retard timing slightly. Changes to the actual 3D color plot were imperceptible, as we basically took about a degree and a half out across most of the board--you can see the final curve here. (Note the extremely high spark advance values at very low rpm--the engine never actually runs at these rpm, so they have no effect except to reduce the visual appeal of the map).
So we've built and installed...
So we've built and installed our own badass, big-stroke LS1. But how much green did we actually blow on this sucker, and how does this compare to other options out there for upping cubes in one's EFI GM ride?
For dyno testing we looked...
For dyno testing we looked once again to Crazy Horse Racing's DynoJet 248H. Though this shop has a definite Mustang focus (as the name suggests), fellow citizens of NJ will be happy to know that these folks also now are in the business of building and installing stroked LS1 engines into hi-po GMs.
With our Thunder Racing tune...
With our Thunder Racing tune loaded into the PCM, our 383-equipped WS-6 spun the dyno rollers hard enough to yield 436.8 hp and 427.0 lb-ft, SAE corrected. This graph is overlayed with our best N/A pull on our stock engine with bolt-ons--indicating that we've already added nearly 100 rwhp! Note the relatively rich AFR, which dips below 12:1 in some places.
After flashing the PCM with...
After flashing the PCM with our adjustments to the fuel injector, spark advance, and PE tables, the Trans Am buckled down again and gave us a mild output increase, bringing totals to an SAE 438.8 hp and 429.2 lb-ft (which come out to 449.2 horses and 439.4 lb-ft if using a standard correction factor in lieu of SAE, if you're curious). Notice that now the AFR is a good bit leaner and hovers in the higher 12s, though we're still richer than we were with our 346-inch LS1.
As things stand, we pretty...
As things stand, we pretty much met the minimums of what we expected in terms of horsepower, noting that more is on the table as further tuning is performed and synthetic fluid is used. This build has not been an all-out dyno and track effort, keep in mind; the point was always to stay streetable and build strong. Nearly 440 rwhp and 430 lb-ft is nothing to be ashamed of, and is almost exactly the same output as the already-legendary LS7 (try pricing one of these suckers out for an engine swap, by the way--it's up there!). But for now, our tune is very safe--just as it should be for a daily-driven street ride.