Pontiac Race Engine - Vintage Brawn

With all of the aftermarket engine parts that have been released over the past few years, HPP has been flush with announcements, overviews, buildups, and tests featuring many of the these new goodies. But for this excursion into Pontiac power, we are taking a more traditional direction.

Those of you who are familiar with Jim Taylor Engine Service know that Jim enjoys building street and race powerplants that use as much of what the factory gave us as possible, and the choice of components for this race engine reflects that sentiment. Here it's the combination of the parts that are key in both making power and maintaining durability.

To that end, Taylor gathered some special factory pieces like a four-bolt main '70 455 block because "the '70 blocks seem to have less core shift than later blocks," he says. Next up was a 428 nodular-iron crank with its 4.00-inch stroke and a set of rare Ram Air-IV heads.

Why a 428 crank in a 455 block? According to Taylor there are a few reasons. "The rod/stroke ratio is better, but there is more to it than that. The loading is different with the 4.00-inch stroke of the 428 versus the 455's 4.210-inch stroke because of the crank's offset--meaning the connecting rod journal is closer to the centerline of the crank. As a result, the engine revs more quickly, seems to be easier on bearings, and just is more efficient. You do get more torque with the 455, but it's not enough of a difference to offset the 428 crank's advantages, especially in a light drag car."

Another aspect to the combination is a longer-than-stock connecting rod that Jim says simply makes for a more favorable rod-stroke ratio that ultimately results in more power.

The Ram Air-IV heads can be worked to flow 300 cfm, and Jim says that 300-306 cfm is what he considers to be safe. "At this level, the customer won't have to worry about water in the ports or other failures," he said. Taylor also related that at 300 cfm and with 320-fps velocity, 440 engines have the potential to produce up to 720 horses.

For the intake ports, Jim described the porting procedure thusly, "The roof is lifted to straighten the port as much as possible, and the cross-sectional area at the pushrod bulge is unified. The port floor is lifted with epoxy about the same amount as the roof was lifted. In the valve pocket, the bowl area is made as concentric as possible. Then the short-turn radius is widened and contoured with a specific radius."

"On the exhaust side, the short-turn radius is widened, and the bowl under the valve seat is enlarged but not bigger than the valve seat area--and that's about it."

However, Taylor warned that the 300-cfm intake flow must be maintained through the intake tract and equalized. To that end, the Victor Dominator intake received a Dittmer turtle and was welded and then ported. "Any unmodified cast manifold, when attached to the head, will have a different affect on each port it feeds. The objective is to have all of the intake valves see the same volume at the same velocity each time the valve opens. This is known as flow balancing. Flow balance and flow charge are major contributors to high-horsepower-to-cubic-inch ratios," Jim shared.

With the intake manifold on the head, flow is 303 cfm and with a header on the head, exhaust flow is 215 cfm. This results in a 70-percent exhaust-to-intake flow ratio. Though 75 to 80 percent has been accepted as optimum over the years, Taylor has found that his engines can make just as much power at this level.

There are plenty more aspects and parts to discuss, but the rest is best done in the captions. All totaled, this combination is worth 659 horsepower and over 600 lb-ft of torque on the dyno. Since Pontiac blocks have been known to split up the middle over 700 hp, at 659 there is a durability cushion built in, and there are bragging rights for getting there with a factory-issue block/crank/head combo.

Taylor builds this combination for a multitude of racers. Since the first engine that we dyno'd was already close to completion when we first saw it, some of the photos here are from a twin that is currently going together, but the recipe is the same. Obviously, this will not be a nut-and-bolt buildup story, but rather a discussion of the more interesting aspects of the engine with dyno results to back-up Taylor's build philosophy.

A set of C&A zero gap rings were employed to increase the efficiency of the combustion process by not allowing the charge to get past the rings through the traditional gaps. Jim explained, "On the intake stroke, the cylinder will actually pull a little more mixture in. On the compression stroke, it will seal better, and on exhaust stroke, there will be better evacuation than with gapped rings. Crank case pressure is also reduced."	Here we can see that the block has been grooved around the cylinder bores to accept O-rings. This is another measure to keep the combustion in the chambers and cylinders and to not have it escape via the head gaskets.	The trick Moroso eight-quart oil pan not only holds more crude for the engine, but it also features an internal baffle to keep the oil at the pickup under deceleration. Taylor related, "The pan configuration is great regarding the accessibility for the starter and headers. With the amount of oil it holds, you can run a full quart low, still have seven quarts, and be guaranteed that the crank won't touch the oil reserve and reduce power.
A Crane 8620 billet solid roller cam, ground to TFX specs, is the brain of the operation with 272/278-degrees duration at .050 and .670/.670 net lift at the valves. Jim's thoughts on the cam, "It gives us about 100 hp per 1,000 rpm, and that's where we wanted to be. The engine doesn't need a lot of rpm, so it will live and make good power and torque."	Taylor was able to get his hands on a blueprint for the Ram Air-IV head. With it, he discovered that the intake port openings were exactly the same size as the Fel-Pro intake gasket and Mr. Gasket 503 gasket, which are used to start the port-match.	Here we see quite a difference in the size of a stock D-port intake port and the modified Ram Air-IV port. Notice via the notches how much smaller the D-port gasket is. For the modified R/A-IV 300-cfm intake port, a Nunzi gasket (shown under the D-port gasket) is used.
The stock R/A-IV chamber shown here features 66cc volume. Though not shown, the race heads have the aforementioned bowl work done and feature 15/30/60-degree angles on the intake seats and the basic 45-degree angle cut into the exhaust seat.	Ferrea stainless one-piece valves are 5.200 inches long to fit the R/A IV heads with the familiar 2.11/1.77 head diameters. But they also feature undercut stems to improve flow and swirl polishing.	Here Mark Erney lowers a Ram Air-IV head onto the block over the ARP studs. A Clark copper head gasket works with the O-rings to keep the cylinder pressure contained.
Here you can see the Comp Cams valve springs and the Crower 1.65 roller rockers. Also note the Nunzi rocker stud girdle that reduces flex of the studs under the high valve-spring pressures. Another big benefit of the stud girdle is that it has a set screw for each Posi-lock so no single one can back off because of its design.	The carb is an out-of-the-box Holley HP 1050 Dominator, but the Edelbrock Victor Dominator intake has been reworked to flow to the potential of the heads. Between the carb and intake is a half-inch seven-layer maple spacer to stop heat transfer to the carburetor.	The distributor is an original Pontiac piece with a bronze gear installed and an MSD Cap-A-Dapt. It works in conjunction with a MSD crank trigger, ACCEL 300+ wires, and a MSD 7AL and coil to maintain timing accuracy.
Here is the nearly completed engine. You can also get a good look at the crank trigger.	These are the custom headers that were welded up by Mark Erney and used in the dyno testing. They are almost equal-length units that feature a 2.00-inch primary diameter, 34-inch long primary tubes, and a 3 1/2-inch collector. Why not equal length? Jim explains, "They were as close as we could get. The problem with Pontiacs and round ports is the huge crossmember under the engine. So to avoid a 90-degree turn, we had to position the number 1 and 2 primaries in front of the crossmember and then turn them under the car to fit the early GTOs. They still worked very well."	In the dyno room, the engine was warmed up to get the oil and water to the proper temperature. C12 108-octane VP Racing fuel was used. Initial pulls were made at 35-degrees timing with #96 jets in place. An oxygen sensor and EGT probe, along with the engine's brake-specific fuel-consumption curve, are used to determine the proper mixture.
Shop owner and dyno master Fred Bitner adjusts the air intake over the carb between pulls.	Here's command central for the dyno. We pried Fred's hands off of it for a second by telling him the air intake over the carb needed adjusting.	The dyno cell is cramped and usually quite warm after a pull. Regardless, Taylor (left) Mark Bitner (middle), and Mark Erney (right) continue to tune the engine to get peak power.

THE BEST DYNO PULL

After adjusting jetting and timing and making six pulls through the course of the day, the best pulls was achieved with #96 jets in the Holley and 35-degrees total timing, which is what the engine started with (for example, a pull with 37-degree timing and #94 jets dropped horsepower by 10 because of a lean condition). Notice that the pull began past the torque peak. This is because the dyno brake couldn't hold the engine at a lower rpm.