1988 Pontiac Firebird Formula 396 Short Block Engine Install - Pumping Up, Part 1
Project Magnum TPI Gets A New Lease On Life WithA 396 Short-Block From Strope Speed Shop.
From the August, 2009 issue of GM High-Tech Performance
By Johnny Hunkins
The basis for any high-horsepower...
The basis for any high-horsepower street car is a good short-block assembly. Our 396 stroker small-block was built by the experts at Strope Speed Shop in Washington, PA. Fuel-injected GMs--and Chevrolet small-blocks in particular--are their specialty.
The basis of our bulletproof...
The basis of our bulletproof 396 cubic-inch stroker was a reciprocating assembly from Lunati (consisting of 5.85-inch 4340 forged Pro Mod rods, custom 4032 forged pistons with .927-inch floating wrist pins, a Pro series plasma moly file-fit ring set, main bearings and rod bearings) and a forged steel 3.875-inch stroker crank from Cola.
Our Cola forged crank (part...
Our Cola forged crank (part No. COLA38753B1, $900) can take a lot more than we're going to dish out for now, but it's nice to know that if we want to add a blower, turbo or nitrous down the road we've got something we can use. The one-piece rear main seal is unique to '86-up small-blocks and features better sealing than it's earlier two-piece counterpart. Note the gun-drilled rod journals--this allows the rotating assembly to balance with considerably less weight, and less weight means better acceleration.
Here is the culprit which...
Here is the culprit which caused us to cut short our plans to add a blower to our stock short-block. These four rod bearing shells show a catastrophic wear pattern (pointed out by the tip of the pen). The small-block Chevy prioritizes oiling from the rear bearings forward; these bearings came off the front two rods which are at the end of the oiling chain.
The Lunati 4032 forging is...
The Lunati 4032 forging is a high-silicon design which is great for the street enthusiast. (A forging is much stronger than any cast or hypereutectic design because the crystalline structure is aligned during the forging process.) Its high-silicon content minimizes expansion, reduces cold piston slap and mitigates oil consumption.
Using a profiled rod like...
Using a profiled rod like the Lunati Pro Mod piece is a good investment on a stroker motor. The contoured shoulders and caps make clearancing the block easier and leave more meat on the block. The guys at Strope also report that the Pro Mod's I-beam construction has proven to be just as strong as a more expensive H-beam rod.
Our Lunati piston features...
Our Lunati piston features a wrist pin which intersects with the oil ring package. To preserve the integrity of the oil rings, Lunati uses a groove lock spacer to bridge the gap left by the wrist pin hole. A locking tab faces down inside the wrist pin hole, keeping it from rotating the gap over the hole.
This comparison of the stock...
This comparison of the stock piston/rod combo (left) with the Lunati stroker piston/rod combo shows the difference in compression height (the distance between the wrist pin and the crown of the piston). The longer stroke means we've gone from a compression height of 1.56 inches (stock) to 1.213 inches, a reduction of .347 inches. We've lost some meat, but by going to a forging we've gained all our strength back and then some. We've also lost a lot of reciprocating weight which translates into free power. Also note that our Lunati rod is longer by .15 inch.
The .1975 added inches of...
The .1975 added inches of rod throw on our Cola crank (bottom) doesn't look like much (that's .395 extra inches of stroke), but it yields 46 more cubic inches with a .030-inch overbore.
After removing and disassembling...
After removing and disassembling our 350 TPI motor, the bare block was taken to the machine shop. After being hot tanked, our new Pro Gram Engineering billet caps were cut to fit the block (called setting the air gap) and the block was drilled and tapped for the splayed caps. The block was then align bored and honed with the new caps in place.
Our block was then bored .030-inches...
Our block was then bored .030-inches over. For final honing, a BHJ torque plate was torqued down with the same example of ROL gasket we'll be using for final assembly. This simulates the stress on the bore with the cylinder head torqued down. All bore distortions are removed in this process--this improves ring seal and power considerably.
Those who follow the exploits of our third-gen Firebird project car can be forgiven for wondering why we're changing directions as of this month. After all, isn't it our motto that when building a project car you should set your goals, make a plan and stick with it? When we initially got our 1988 Firebird Formula 350, we started modifying the Tuned Port 350 engine like many of you would: first the cheap and free stuff, then some easy bolt-ons, culminating most recently with a cam, ported heads, and a ported TPI manifold (see "Getting Serious," November 2000).
Our next plan for the engine was to push the bolt-on theme even farther with a Vortech S-trim supercharger kit and fuel system upgrades. But as fate would have it, days before the blower kit was supposed to arrive, we were greeted with the wonderful sound of rod knock. In case you're wondering, the sound of rod knock is not a good portent for adding another, oh, hundred rearwheel horsepower via a blower kit.
Behind schedule and faced with repeated driveability problems (see "Fine Mess," August 2001), we thought we were finally seeing the light at the end of the tunnel. Well, that "light" turned out to be a train. Our original goal of building a semi-affordable "bolt-on" car was going down faster than the Titanic. The idea was nice; many third-gen owners are on a budget and prefer to spend at a moderate pace when making upgrades. It's not that budget-minded enthusiasts like to go any slower than their rich counterparts, it just takes a little longer and sometimes takes a more tortuous route. (The word "tortuous" definitely applies to us!)
Perhaps if we were more virtuous, we would've located another used stock engine or perform a stock rebuild of the existing engine. We thought about it, but decided against either option. To make a long story short, we opted to go with a naturally-aspirated 396 cubic-inch stroker with bullet-proof parts and superior induction. (For the full story on why we chose a naturally-aspirated stroker, you can log on to www.gmhightechperformance.com.)
The decision to build a stroker engine is fairly straightforward, the really hard part is selecting the right parts for the short-block, induction, ignition and engine management. As fun as it is to pick parts out of a catalog, more often than not, this can lead to disastrous results if you don't know what you're doing. And while most people like to think they know what's going on (us included), they really know just enough to get into trouble. For this reason, we asked the good folks at Strope Speed Shop (Washington, PA) to help select our parts and assemble our engine.
Having seen many of Strope's previous projects, we had a good idea that they were in tune with what we wanted. As the parts selection proceeded, we discovered that Bill Strope Sr. and his son Aaron were very meticulous. Our busy schedule offered plenty of opportunity for us to forget about the many minor needs of the project, but Bill and Aaron were on the ball with regular communication via fax and e-mail. They made sure that every part was ordered properly and every "T" was crossed. By the time we were ready for our short-block photo shoot, there was no stone left unturned. Of all the positive things we can say about Strope, the logistics and planning impressed us the most--a big factor for us given the long travel distance involved.
As we alluded to earlier, Strope specializes in building really hot fuel-injected street-legal GM machinery. In short, building this kind of stuff is not a side project, but the main deal. When we told them we wanted a stroker, they already knew what to do. The short version is that we wanted a street-legal naturally-aspirated EFI motor with a wide powerband that would be capable of pushing us into the high 11s. To get that, Aaron Strope recommended that we go with the biggest small-block practical with the cylinder case we already had.
Aaron says, "There's really nothing special about the number 396, it's just not any more expensive to build than a 383. The side benefit is that a 396 has a little bit more bottom end than a 383. When you go bigger, you get to the point of no return. If you go to a 409 you won't make that much more power because you can't use a SuperRam and you don't have a street motor any more. You can't really go up on the bore with a stock block, so you have to go with a bigger stroke and you need to do a ton more clearancing on the bottom end. The 396 is really the right size for a stock-block stroker." (We'll cover the induction in more detail in part 2, but it bears repeating that the SuperRam was a key breathing component for our stated goals. It doesn't make any difference how big the holes below the deck are if what's on top can't supply the air.)
To obtain 396 inches, Strope retained the original block, opting to machine it to handle the added bore and stroke. The stroke, in this case, came from a bulletproof Cola forged crankshaft with a 3.875-inch stroke. "This was our first time using a Cola crank, and the forging and the machine work looked really good," says Aaron Strope. "The fillets looked good and they did a nice job contouring the counterweights. They also radiused the oil holes and they lightened the throws by drilling the 1 and 4 rod journals.
"I was really impressed with the spec sheet--they measure each crank by hand and write it on this sheet. They also check the stroke with a computer. This makes my job as an assembler pretty easy. I think we'll be buying Cola cranks in the future for some upcoming projects. We weren't that happy with the packaging, however. The crank seemed pretty unprotected in its cardboard box, but it arrived just fine from UPS."
The Cola crank is one of the few in the industry to be offered with a one-piece rear main seal. Even though all OEM small-blocks made after 1986 came with a one-piece rear main, most crank manufacturers build the older two-piece design, citing the preponderance of race cars still using the older design. Late-model owners, however, are reluctant to retrofit the older design due to its poor sealing and frequent maintenance. Cola actually offers two styles: standard, and lightweight. The lightweight version (which we chose) features gun-drilled rod journals for greater power.
For reciprocating components, Strope chose Lunati. Among those parts were Pro Mod forged 5.85-inch rods. "Lunati stuff is really good quality," states Aaron. "We've used it before and it's really tough to find a good rod like the Pro Mod at this price. It's got a profiled contour which allows you to clearance the block easier, it's lighter and it maintains the same strength as a more expensive H-beam rod."
Lunati Pro Mod rods were teamed with a set of custom forged 4032 pistons. To get the desired zero-deck clearance with the 3.875-inch stroke, Strope specified a 1.213-inch compression height. This places the .927-inch wrist pin with our 5.85-inch rod just inside the oil control ring pack. To shore up the oil pack, Lunati uses a special bridge ring with a locking tab that faces down in the wrist pin bore. It's a rather elegant solution to a weak area in the piston. Strope also specified a 4.030-inch bore and dual valve reliefs (totaling 4cc) to produce a final compression ratio (with the intended 64cc AFR heads) of 11.69:1.
"The 4032 Lunati piston forging allows you to use a tighter piston-to-wall clearance and that makes the engine quieter," states Aaron Strope. "A race-series forging would have a lot of piston slap because it would have almost twice the piston-to-wall clearance. In terms of strength, the 4032 alloy is nearly as strong as a 2618 race piston. What little the 4032 gives up in strength, it gains in dimensional stability. I think it's the strongest truly streetable piston you can get."
With a sizable investment in the rotating assembly, it only makes sense to keep it all in place when things get frenetic. Consequently, Strope was absolutely insistent on the use of Pro Gram Engineering billet main caps. These four-bolt splayed pieces replace the stock cast-iron two-bolt caps and require the block to receive extra machining steps. The Pro Gram caps are not only far stronger than the stock ones, they also shore up the webbing by having an extra pair of splayed bolts on each of the interior caps.
While we were at it, we also ordered the 2-bolt billet front cap for extra strength. (Pro Gram also offers a billet rear thrust bearing cap which is excellent for power-adder cars, but Strope felt the stock rear cap was already sufficient.) We were happy to discover that Pro Gram offers their splayed conversion kit specifically for late-model applications where the stock oil pan and dipstick must be retained. This saved us a bundle because we didn't have to upgrade to a custom oil pan--an otherwise unnecessary expenditure for a low-rpm street application.
Last, but certainly not least, is the importance of a high-quality, high-tensile strength fastener. Once again, Strope was adamant, and insisted on using Automotive Racing Products' studs with 6-point nuts (for the inner cap fasteners) and 12-point bolts (for the outer splayed caps). We will also be using ARP fasteners for the remainder of the engine build-up including head bolts, oil pump drive, oil pump stud kit, balancer bolt, flex plate bolts, and torque converter bolts. As you can tell, we don't plan on stuff moving around much once we torque it down!
There's a lot more coming in the issues ahead. Next time we'll follow up with camshaft, valvetrain, oiling and induction. We'll look more closely at our horsepower and airflow goals and reveal our strategy for leapfrogging into the 11s.
For more info on the Magnum TPI 396 short-block, log on to www. gmhightechperformance.com. There's a lot more than meets the eye!
Cola crankshaft, part No. COLA38753B1 $900
Lunati Pro Mod connecting rods, part No. LAB1 $699
Lunati custom forged 4032 alloy pistons $599
Lunati ring set, part No. P14035 $99.95
Lunati rod bearings, part No. CR848HP $59.95
Lunati main bearings, part No. MB5142HP $59.95
Pro Gram Engineering main caps, part No. SB350C12 $239.95
Pro Gram Engineering front main cap, part No. SB350F $79.95
ARP 12-pt. main bolts (outer), part No. 234-5201 $136.95
ARP main studs (inner), part No. 134-5401 $43.48
machine work (block & balancing) $900
We wanted a zero-deck block...
We wanted a zero-deck block for our 11.6:1 compression ratio and flat-top Lunati pistons. The Cola crank and Lunati rotating assembly are mocked up in the block with the bearings and a measurement is taken to find out how far the piston is below deck. (Most factory assemblies are .025 below the deck surface, or "in the hole.") In our case, the pistons were found to be .023-inch below deck. The deck was then shaved 23 thousandths to obtain a zero-deck surface.
Prior to balancing, the individual...
Prior to balancing, the individual weights of each part are obtained (rods, pistons, pins, locks, rings, bearings, and the thin film of oil on the rod bearings), and equivalent bobweights are placed on the crank throws. Here the crank is being spun by a computer balancer which will determine how much weight should be either added or removed from the crankshaft counterweights. This will allow a neutral-balance flexplate and balancer to be used which cuts down on harmonic vibration and stress at higher engine speed.
Here, the crankshaft counterweight...
Here, the crankshaft counterweight is being drilled so that a slug of Mallory metal can be added. Mallory alloy is approximately twice as dense as forged steel so not much is needed to create a neutral balance.
After the block was machined,...
After the block was machined, Aaron Strope used an ABS block clearancing bar to clearance the bores for the extra stroke. The ABS block-clearancing tool (which comes with a Dewalt industrial die grinder) is more cost-effective than a Bridgeport or CNC process but produces the same great result. Now is also a good time to deburr the rough casting on the outside of the block and in all rough-cast areas.
After all machining and clearancing...
After all machining and clearancing is performed, Aaron thoroughly washes the block to remove all metal particles from the nooks and crannies. This includes using a series of bottle brushes in all the oil galley holes. This process was repeated on several occasions when clearancing--an iterative process--was performed.
Prior to engine assembly,...
Prior to engine assembly, Strope paints the lifter valley and area under the timing cover with Glyptal, an electronic insulator coating. Glyptal also sheds oil very well and holds up to heat, making it an excellent coating for this use. When this was completed, Strope masked the block and gave it a few coats of gloss red to match the car.
Here Aaron Strope measures...
Here Aaron Strope measures piston skirt-to-cylinder clearance. Our Lunati 4032 forgings don't require as much clearance as a full-race 2618 alloy piston. Ideally, Aaron likes to see between 3 and 4 thousands clearance with this alloy.
It's important to check the...
It's important to check the rod clearance for each cylinder prior to ring installation and final assembly. There should be a minimum of 60 thousandths clearance between the rotating assembly and cylinder bores, pan rails and cam journals. (There are technically seven places where interference can happen for each rod. With 8 pistons that's 56 possible trouble spots!) Aaron says the cam clearance issue is the most compelling reason for using a small base-circle cam like the one we're planning. It's important to check clearances with the piston and rod assigned to that bore--you can get into trouble if you use the same assembly on each cylinder.
For rod side clearance Aaron...
For rod side clearance Aaron likes to see sixteen thousandths, but 14 to 20 thousandths is acceptable. Each set of rods needs to be checked with an accurate feeler gauge. We were dead-on with the side clearance at 16 thousandths.
Crank end play is critical--too...
Crank end play is critical--too tight and the thrust bearing will burn up and create extra friction, too loose and the crank will move longitudinally and cause the rods to bind on their journals. The acceptable range is 3 to 8 thousandths, but Aaron prefers it to be on the tight side of this range. Our Cola crank was around 2.5 thousandths, a tad too tight even for Aaron. The binding was cured later on when it was discovered the thrust bearing diameter (No. 5 main) was too tight and a thousandths-over bearing was substituted. The larger thrust bearing produced a 4.5 thousandths end play.
On main bearings 1 - 4, we...
On main bearings 1 - 4, we were shooting for 2.5 thousandths bearing clearance and on bearing number 5 (the thrust bearing) we wanted 3.5 thousandths. More clearance is required for No. 5 because it feeds oil to bearings 1 - 4 as well as all the rods. When installing main bearings, make sure you pay attention to placing the upper and lower halves in the right location. Failure to do so will cut all lubrication to the main bearings.
Getting the main bearing clearance...
Getting the main bearing clearance is achieved by subtracting the outside journal dimension from the larger inside dimension. We ordered our Lunati bearings in standard, one thousandths under, and one thousandths over dimensions. This allowed us to measure the clearances and adjust the bearings for optimal oil clearance. Aaron ended up using the standard bearing in No. 1, and one thousandths over for 2 through 5. Keep in mind that whenever you change the No. 5 bearing (the thrust bearing) you must go back and check crank end play.
Rod bearing clearance should...
Rod bearing clearance should all be 2.5 thousandths. As with the main bearing caps, the rod caps should be torqued to spec before measuring. Rods should be torqued on a rod vice so that the caps are square to the rods. Rod bearings should be installed with the chamfered side facing the journal radius. Rod bearings are also marked upper ("U") and lower ("L") indicating which halves goes on the rod and the cap.
To obtain the rod clearance...
To obtain the rod clearance the outside rod diameter is subtracted from the inside rod diameter (shown). As with measuring the outside main journal diameter, the outside rod journal diameter should be checked in a location away from the fillet radius and oiling holes.
The top and second rings must...
The top and second rings must be file fit in a ring filer and checked inside the bore periodically during fitment. The ring filer ensures that the ring end is filed perpendicular to the plane of the ring. It also makes the gap completely even from the piston to the bore.
The Lunati ring set uses a...
The Lunati ring set uses a moly top ring and a ductile iron second ring. For naturally-aspirated street applications, Aaron suggests using a top ring gap equal to 4.5 thousandths per inch of bore, and on the second ring 4 thousandths per inch of bore. (Our 396 got 18 thousandths on the top ring and 16 thousandths on the second ring). For nitrous, blower or turbo applications where combustion chamber temps are higher, more gap is preferable--5.5 to 6 thousandths per inch of bore on the top ring and 4.5 thousandths per inch on the second ring. Race engines with more compression--and thus more heat--should also get more end gap. The extra gap allows the ring and cylinder wall to expand more before binding occurs.
Once file fit, Aaron installed...
Once file fit, Aaron installed the Lunati rings with this handy ring fitter which prevents damage to the rings during installation. The top and second ring are clocked 180*--the oil rings and the wrist pin bridge ring also have specific clocking requirements. Regardless of your ring manufacturer, pay close attention to the recommended ring clocking, or else your power, ring wear and oil consumption may be less than expected.
Our Pro Gram Engineering...
Our Pro Gram Engineering billet main cap kit is designed specifically for use in street applications where a stock oil pan and dipstick is used. We also opted for the billet front main cap which gives us more strength, but is not splayed like mains 2 through 4. Pro Gram also makes a billet one-piece-seal rear cap which is great for supercharged, turbocharged and nitrous applications. We opted to use ARP studs along the center and ARP bolts for the splayed outers. Aaron torqued the main caps from the center and worked outward; center studs to 30 ft.-lbs., outer splayed bolts to 30 ft.-lbs., center studs to 70 ft.-lbs., and finally outer splayed bolts to 65 ft.-lbs. Note that these torque values are only good with moly assembly lube. Assembly with motor oil will raise torque requirements significantly.
We used a good moly assembly...
We used a good moly assembly lube throughout our engine build-up--in this case synthetic bearing assembly lube from Royal Purple. This aids engine break-in by providing crucial lubrication during the first few seconds of engine operation before oil reaches the bearings. A synthetic also provides a higher film strength which is also critical at start-up. Here Aaron applies assembly lube to the rod bearing prior to installation in the engine.
By now, each piston/rod assembly...
By now, each piston/rod assembly has been assigned to a specific bore and its bearings and rings have been sized and oriented for that specific bore. (i.e. now's not the time to turn the thing upside down or move it to another bore!) Here Aaron taps the piston assembly into the bore using a tapered ring compressor and a piston knocker, both from Powerhouse Products.
After hand-tightening the...
After hand-tightening the rod bolts, insert a feeler gauge between the rods (both sides of the block) to align the cap while being torqued. This shim is nearly the same thickness as the rod side clearance value, but may be a bit less with assembly lube in place. The rod caps should be torqued in 10 ft.-lb. increments up to 60 ft.-lbs. using moly assembly lube.
Pro Gram Engineering
P.O. Box 472
Automotive Racing Products
1863 Eastman Ave.
Holley Performance Products (Lunati)
1801 Russellville Rd.
P.O. Box 10360
Cola Crankshafts Inc.
19122 South Santa Fe Ave.
Royal Purple Motor Oil
23763 Royal Purple Lane
STROPE SPEED SHOP
190 East Murtland Ave.