Inside the engine, carefully...
Inside the engine, carefully planned modifications were made to control oil drainback in an effort to keep oil off the rotating assembly. The cam tunnel was closed off at the bottom and oil directed forward, while the lifter valley was modified to only allow oil return via the front cover.
Other tricks in the short-block were aimed at strategically controlling the oil with the required wet sump oiling system. Plates were fabricated to close off the bottom of the cam tunnel, preventing the oil in that area from draining onto the crankshaft. A drainage provision was machined into the cam tunnel below the bearings to allow the oil to drain to the front of the engine. Likewise, the drainbacks at the upper portions of the engine were blocked off at the rear of the block, and all the oil was directed to the front of the engine. A plate was built to bolt onto the front main cap, which compartmentalized the oil return away from the crank. Everything was routed so that the returning oil would not get anywhere near the crank. As Chris says: “The oil control allows you to have less oil in the pan, and of course, the crank can spin a lot easier if it doesn’t have to spin through oil. You will definitely see less oil thrown on the cylinder wall, especially with the long stroke crankshaft.”
Heads, Induction, and Cam
Of the key components that define this engine combination, the CHI 3V Cleveland heads played a major role. Chris tells us: “The CHI head is not the only production-style head, but given the ability to flow 400 cfm on the intake side with that small of a port and intake valve, then it is just what we want to run. There are better cylinder heads out there, but they are not strictly production-style heads. As far as modifications, we sized them for a certain rpm. To make power at a certain rpm, we had an idea of where the port needed to be sized. The ports were actually epoxied to shrink the port. At first we ran them as-cast, and then kept adding epoxy until the overall power score began to decline. With that experience, we can get closer considering the cam selection right off the bat. We learned a lot over the years, especially in light of the requirements of the competition and the wide operating range required. We actually had a smaller intake valve in the head earlier in the development, but later found the bigger valve added power to the top end without hurting the bottom end numbers.”
Sizing the intake ports to...
Sizing the intake ports to the rpm range was just as important as the overall flow. The SAM team experimented on the dyno to zero-in on the optimal port size by progressively filling the intake port floor with epoxy to reduce the volume.
The CHI package features a corresponding intake manifold, in this case a Dominator-flanged single-plane unit. Chris detailed the intake mods: “Since our combination was fuel injected, we didn’t have to do a lot of runner tuning, since we could do that on the EFI. The manifold was ported and epoxied to match the heads, and that’s about it. It is just a nice-looking manifold.” To feed the intake, a Holley EFI system using a 2¼-inch Dominator throttle body was selected. Chris tells us that his experience with the Holley system came about as a result of a dyno test done at the school using the Holley EFI: “I was very impressed with the usability of the Holley EFI. The system was much simpler even for a novice than some of the other systems out there. I liked the fact that the fuel tables were in lb/hr, rather than in VE, making it easier to transition from a carb to the EFI system.” All of the porting development on the intake manifold, as well as the cylinder heads, was performed in-house at the School of Automotive Machinists.
At the front main cap, a baffle...
At the front main cap, a baffle was fabricated to separate the returning oil from the rotating assembly, effectively creating a closed return system. Any gain in windage reduction equals free horsepower.
Interestingly, going by conventional...
Interestingly, going by conventional theory, smaller intake valves were initially used in an effort to maximize low-rpm performance. Eventually, the team found that up-sizing the intake valve to 2.19 inches added top end power with no corresponding loss at the bottom of the rev range.
The cylinder head of choice...
The cylinder head of choice was the Cleveland-style CHI 3V unit. In terms of efficient flow versus port cross-section, these heads work extremely well. All of the cylinder head modification development work was performed at the School of Automotive Machinists.