396 Stroker Motor - Air Induction - Pumping Up, Part 2

This month, we continue our 396 stroker build-up for our 1988 Firebird Formula project car--dubbed Magnum TPI. Those following along will remember that we covered the short-block build-up of our 396 at Strope Speed Shop in the September issue of GMHTP. In that installment, we documented Aaron Strope's careful machine work and assembly using a Cola forged 3.875-inch crank and Lunati internals (Pro Mod forged rods, custom 4032 alloy pistons, chromoly rings, bearings, wrist pins and locks). To strengthen the bottom end, we also threw in a set of billet main caps from Pro Gram Engineering and used Royal Purple synthetic assembly lube at all stages.

With a strong bottom end like this, we aren't about to put junk breathing components on top. A stroker small-block needs to breath big-block numbers, or else it will fall flat on its face. Flying seemingly in the face of big power are two other requirements heaped on top: excellent street manners and the ability to pass the strict New Jersey IM240 emission inspection program. If that isn't enough, we would really like to run 11s with pump gas, but we may have to settle for very low 12s. Phew!

Third-gen TPI fans out there already know that making power with a factory TPI is like squeezing water from a stone, so we realized early on that it was folly to even try. Several of you have been quite emphatic on the various internet message boards about us trying the ACCEL SuperRam manifold, with the rest of you urging us to use the TPIS MiniRam. Both are excellent pieces, but we decided to fall on the side of big torque (the MiniRam tends to excel at the upper end of the power band where race cars inhabit). Not that a stroker motor would have any trouble making torque with a MiniRam, it's just that our camshaft selection and planned street gearing favored the torquier SuperRam.

Clearly, we weren't blazing a new trail. Many others over the past seven or eight years have gone before us to point the way, all we had to do was read the burnout marks on the asphalt. Turns out, many of those tracks were aided by cylinder heads from Air Flow Research. Our previous cylinder head flow test (see "Just The Facts," Sept. 2000) revealed that AFR have clearly done their homework, so we ordered a set of emission-legal AFR 190 heads, but with a twist. Needing a larger port, but wanting to live within the letter of the law, we had AFR perform a competition CNC port job, which enlarged the intake port volume to 195 cc.

AFR's 190 head is a direct bolt-on, requiring no special intake manifolds, valvetrain hardware or headers. Rick Sperling of AFR told us that the exhaust ports are raised .125 inch which in most cases is not enough to cause problems with header fitment. Exhaust port volume is increased to 70cc, and the cross section changes from a "D" shape to a square, which accommodates the exhaust flow to a set of 13/4-inch headers (like our SLP units) just perfectly.

After Strope Speed Shop received our tweaked AFR 190s, Aaron Strope massaged them further while porting the SuperRam's runners and plenum area. The result was an intake port that flowed 279 cfm at .500-inch lift without the use of a radiused inlet fixture (see airflow data sidebar). If we calculate a conservative 3 percent flow increase with a radiused inlet, we pass our target airflow by 2 cfm and at .050-inch less lift! Even better, the intake port volume now measures only 198cc after Strope's additional port work. These are heads that are clearly capable of getting us where we want to go.

One of the cornerstones of engine building is the principle that the better the cylinder head, the fewer compromises have to be made in the camshaft. This is a vast oversimplification, but it serves to point out that for our street motor, the only way to achieve our stated goals is to put the most resources into the cylinder heads. In this department we didn't skimp, spending a total of $2724 including all our port work at Stropes ($1924 for the CNC-ported heads and $800 for additional porting and shimming the spring heights). Naturally, if you're willing to settle for less performance or if you can perform much of the work yourself, you'll do better on the price, but this was one area we were unwilling to sacrifice. Perhaps of all the gear we chose, we wrangled with the cylinder heads the most, not on the grounds of performance, but on the grounds of cost. We know many third-genners out there can't afford heads like these, but it's impossible to achieve serious performance without a good set of heads (our last fiasco ought to be proof enough of this). If you only take away one lesson from this story, let this be it!

Excellent cylinder heads sure made camshaft selection a lot easier. For this, we turned to the Competition Cams tech hotline. We fed Comp all our data, including our projected compression ratio and goals of streetability and emissions, and they developed a custom cam profile specifically for our SuperRammed 396 stroker. The split-pattern hydraulic roller cam they suggested specs out to 224*/230* at .050-inch lift while valve lift tops out at .536 inch on the intake and .544 inch on the exhaust (with a 1.6:1 ratio Pro Magnum stainless steel rocker). We also ordered a .10-under double-roller timing set for align-bored blocks, hardened pushrods, anti pump-up hydraulic roller lifters and a hydraulic roller conversion kit which supplied new lifter link bars, a lifter retainer assembly and fresh camshaft thrust plate.

One other key feature that we designed into Magnum TPI's 396 is a complete Evans cooling system. This consists of Evans NPG coolant, a high-flow Evans coolant pump (don't call it a water pump, there's no water!), an Evans radiator and larger coolant hoses. While most cars will benefit from using just the coolant alone, we wanted the maximum benefit in the hope that this will turn into extra power when the calibration is completed. This expectation is not unfounded: similar engines to ours have seen as much as 20 additional horsepower from increased octane tolerance and better thermal efficiency. We'll go into the theory in Part 3, but suffice it to say that Evans' customers have noted significant gains in fuel-injected applications and we think this high-tech solution is completely appropriate for both this application and our readers.

Using our Mr. Gasket Desktop Dyno simulator, we plugged in our engine specs including cylinder head flow numbers and our cam timing from our Competition Cams cam card. According to other users, the one area Desktop Dyno doesn't seem to model very well is the SuperRam intake. SuperRam proponents tell us Desktop Dyno falls far short in its torque estimate and that we should see another 40 or 50 lb.-ft. at peak torque. Even with this attenuating factor, the simulation projected 470 hp at 6000 rpm and 480 lb.-ft. at 4000 rpm using the "tuned port" induction model with small headers and mufflers. Providing we see the missing torque in the real engine, we should easily go 12-ohs with the proper gearing and torque converter.

The optimal programming will probably push Magnum TPI into the 11s, thanks to a new Gen VII DFI with wide-band tuning control. For the time being however, we're soldiering on with the stock ECM and a custom computer chip. It will be interesting to see just how much power the new DFI will be worth over an expertly-programmed PROM chip with a stock ECM and mass air flow meter. All that's coming up in the January and March 2002 issues of GMHTP, so keep your eye peeled here for details. For now, let's watch Aaron Strope perform the top-end assembly of our new 396 at Strope Speed Shop.

We ordered an OE hydraulic roller rebuild kit from Comp (part No. 08-1000) which includes new factory items like a camshaft thrust plate, thrust plate bolts, lifter link bars and lifter retainer assembly (also called a spider). On an older motor like ours, it's a good idea to replace these items which get worn out after a while. The new thrust plate bolts were dabbed with Lock-tite and torqued to 96 inch-lbs. When installing the timing set (part No. 3100-10, .010 under for align-bored blocks) put the number 1 piston at TDC and align the sprockets' index dots across from each other.	Comp Cams grinds all their computer-controlled hydraulic roller cams with 4* advance, so Aaron is installing the cam straight up. However, you should never take anyone's word for it; always verify the cam spec by degreeing in the cam. It's a small inconvenience but may save you lots of trouble down the line. Here Aaron is adjusting the degree wheel to show "zero" on cylinder No. 1 TDC. To zero the wheel, adjust it so that it reads the same number of degrees when the No. 1 piston bottoms out on the stop when the crank is turned in both directions.	We found our intake lobe was actually ground with a 109* lobe center angle, that's one more degree advanced than advertised (a four degree advance would put it at 110*). We weren't too concerned about this as it should only lower our torque peak by 100 rpm--not enough to make a noticeable difference. The rest of the valve opening and closing events were right on with the cam card, so we moved on without changing the cam position. Once the cam is degreed, the cam bolts can be removed individually and retorqued (20 ft.-lbs.) with Lock-tite.
We chose to use an ATI damper (part No. 917780) for our 396 because it meets SFI spec 18-1 (required for cars running 10.99 or quicker) and because it will extend the lifetime of our bearings and provide a smoother accelerating, more powerful engine. Stock dampers typical only work up to about 4500 rpm. At higher rpm OEM dampers stop dampening and the bearings really get hammered from the combustion pulses. A good damper like the ATI works all the way up to 10,000 rpm and can be worth an extra 10 hp on a motor like ours. Our particular damper is made for motors with a stroke longer than 3.75 inch; longer stroke cranks have more mass to control and this requires additional material in the internal damper ring.	Aaron finished up the bottom end by installing the rear seal adapter ('86 and newer only) and the stock oil pan (which was cleaned and repainted prior to installation). Strope used an Ultra-Seal one-piece oil pan gasket set which includes serrated fasteners (part No. 6561). Aaron says he likes the Ultra-Seal gasket because it has steel crush sleeves lining each of the bolt holes. These prevent the gasket from squishing out or being over-torqued (either of these problems can lead to leakage). Torque the smaller rail bolts to 100 inch-lbs. and the corner bolts to 15 ft.-lbs.	Up top in the lifter valley Aaron installs the new Comp Cams anti-pump up hydraulic roller lifters (part No. 875-16). These are good for higher rpm use (up to about 6700 rpm) and prevent the lifters from pumping up and floating the valves. We expect to see 5700 to 5800 rpm; that's about 1000 rpm higher than the stock TPI motor. In this view you can see the rest of the Comp Cams hydraulic rebuild kit (spider and link bars) we mentioned earlier.
Imagine that, another trick tool from Powerhouse Products--this one measures the installed height of the valve springs. Aaron Strope is setting up our ported AFR 190 heads with a 1.900-inch installed height which provides 120 lbs. of seat pressure and roughly 360 lbs. at our target .550-inch lift. First Aaron obtains the height measurement without shims using the same retainer and keepers that will be used in that valve. He then calculates the necessary shim thickness to obtain the proper installed height for that valve.	Strope Speed Shop has built a unique porting station that features extensive bottom lighting. This allows Aaron Strope to better visualize the port shape as he develops it. One of the keys to building power on a street engine is to maximize airflow through a minimal port cross-section or port volume. Anybody can hog out a port for increased flow, but to do so without increasing the port volume is where the challenge--and the horsepower--lies.	When you start out with a great port shape like the CNC-ported AFR 190, it's a lot easier to make good power. Our choice of AFR heads was driven by our desire to keep Magnum TPI emission-legal (the AFR 190 has provisions for EGR) and by the excellent results we obtained in our head flow comparison test back in the September 2000 issue. AFR offers a 195 and a 210 version, but neither has provision for EGR. To get around this, Rick Sperling at AFR ran a pair of their emission-legal 190 heads through the CNC machine with a 195 cc competition port program, thus giving us the airflow of their larger race head in a street-legal application.
Strope used the AFR CNC job as a starting point for additional porting to achieve the desired flow target. This isn't something you want to do yourself unless you've had a lot of experience (which usually means messing up a lot of heads before getting it right). Aaron used a die grinder with an aluminum helix burr, followed by a sand roll to smooth the port shape. The valve job on the 2.02/1.60 stainless valves was left as it came from AFR, but Aaron did shim the springs and check them for coil bind.	After porting the heads and intake, Bill Strope Jr. took our pieces to Extrude Hone's facility in Irwin, PA to have them checked on a flow bench. The porting work performed by Aaron met our airflow goal with no problem, which took a load off our mind. Due to time constraints, no radiused fixtures (on the intake) or flow extensions (on the exhaust) were used by the Extrude Hone staff--much to our dismay. Even without a radiused inlet, the intake port flowed 279.4 cfm at .500-inch lift, a figure that would be 3 to 5 percent higher had a proper clay radius or a Brezinsky fixture been used. We estimate the true intake port flow to be somewhere between 287 and 293 cfm, well over our 285 cfm goal with our 195 cc port.	Using a graduated burette, Aaron Strope measured the combustion chamber volume at 64.25 cc, that's pretty darned close to the 64 cc spec we requested from AFR. The piston clearance volume measured 4.5 cc, about a 1.5 cc larger than we expected. We believe this is due to a minor discrepancy in counting the crevice volume above the rings. When we plug into the formula ROL's head gasket clearance volume of 10.1 cc and our cylinder swept volume of 791.16 cc, we get a compression ratio of 11.03:1. That's a bit shy of our 11.6:1 target, but--with gas prices going up--it gives us a little bit more octane tolerance and that's fine with us.
We used ROL Pro-Torque head gaskets (part No. HG31000HT) which feature a Grafoil facing material. This aids sealing even under low torque conditions when head bolts may have relaxed, helping to prevent head gasket failure. A stainless steel fire ring provides resistance to high combustion temperatures and a silicone outer coating provides better cold sealing during start-up and warm-up.	For fasteners, Aaron used an ARP 12-point bolt kit (part No. 234-3701) which are rated up to 195,000 psi tensile strength. Here Aaron torques the ARP bolts in a stepped sequence of 20 ft.-lbs., 40 ft.-lbs, and then twice at 75 ft.-lbs. Aaron used ARP Thread Sealer which has a Teflon sealer and moly lubricant to produce the proper clamping load on the gasket for the rated torque reading. Note the sequence diagram which Aaron uses for reference.	We decided to step up to a set of 1.6 Pro Magnum rockers from Comp Cams. These replaced our Magnum roller tipped investment cast pieces we previously had. The extra strength will be needed with the extra rpm capability and increased valve spring pressure of the bigger camshaft. When adjusting a hydraulic roller rocker at zero lash, the lifter should be on the base circle of the cam lobe and the nut should be tightened until the slack is completely out of the pushrod (to check the pushrod, rotate it between your thumb and finger). Aaron then preloads the nut by an additional 180* and tightens the recessed poly-lock. Note that we did have to clearance the supports inside the factory valve covers in order to clear the larger rocker arms.
Before installing the intake manifold, it's important to trim the intake gasket even with the intake port wall on all four sides (we're using ROL gaskets, part No. MS101B). Any part of the gasket that protrudes into the airflow stream will disrupt flow and hurt horsepower, so it's effort well spent.	After running a bead of silicone RTV along each end on the manifold valley, Aaron carefully placed the intake manifold down on the intake gaskets. The intake bolts are then torqued to 35 ft.-lbs.	We replaced the old 22 lb./hr. factory injectors with new ACCEL 26 lb./hr. injectors (set of eight, part No. 150826). This increase in size will satisfy the demand of 500 naturally-aspirated horsepower while staying lean enough at idle to pass the emission test. We also ditched our old adjustable fuel pressure regulator which was found to have a broken diaphragm screw and a corroded diaphragm spring. Our new unit from ACCEL (part No. 74750) also has an adjustment screw that is easier to access once installed.
Installing the SuperRam runners isn't as easy as it looks in this photo. Aaron Strope and technician Roger Creech spent about an hour prepping the runners prior to installing them. This consisted of enlarging the bolt holes, massaging the Allen head fasteners (some needed to be cut slightly or the heads narrowed for clearance), and removing some of the rocker arms to get at the lower runner bolts. Note that the EGR valve and sensor pigtail has already been swapped over from our old manifold.	The key to making big power with pump gas is our use of Evans Cooling System components throughout. This Evan coolant pump (part No. EP3122R) is designed for reverse rotation serpentine drive small-blocks like ours. One of its key features is a high-volume pump vane, which is required to move the maximum amount of coolant. We also plan on using larger-than-stock diameter upper and lower hoses, Evans NPG coolant, a high-capacity Evans radiator and a small-diameter (overdriven) Evans pump pulley. Note that the coolant pump is actually cast iron but we have painted it with aluminum paint to match the rest of the engine.	Lots of work went into putting on the box half of the SuperRam intake. There are 16 small screws that must be installed from the bottom and many of the bolt holes don't line up! Just take your time and work the screws in one at a time--don't tighten any of them until they're all installed. It may be necessary to loosen some of the runners at the base to match the holes up (that's one of the reasons why the valve covers are still off). You can see from this view the beautiful port work Aaron Strope did on the SuperRam runners.
We weren't too happy with the quality of the SuperRam lid, but we've heard plenty of comments from others along the same lines so we weren't that surprised. The problem is that the casting is nowhere close to being flat and that causes massive vacuum leaks. We know we'll need to spend plenty of time with this later on when the motor goes into Magnum TPI--we'll probably have to use lots of RTV and/or extra gaskets. Some SuperRam users opt to fabricate their own lid from flat aluminum stock--a good idea we think.	After 13 years, we think the stock HEI distributor has had it. We obtained an ACCEL Billetech HEI distributor to replace it (part No. 60109) which will go nicely with our existing ACCEL Super Coil and our new ACCEL 300+ ignition system. We suspect that our old distributor was giving us problems at higher rpm due to a rotor phasing problem. This should help cure that problem, among other things. If we decide to take advantage of the sequential injector control in the Gen VII DFI, we may have to change over to an MSD dual-sync distributor later on and get rid of the HEI ignition entirely.	While our engine was out of the car, the crew at Strope's cleaned 13 years of crud out of the engine bay and then spray bombed it in preparation for the new engine. We want the rest of the car to look as good as the engine and now is the best time to take care of this little detail. We can't wait to see the SuperRam 396 between those fenders.