Coatings were used extensively throughout the TPIS Challenge entry. Here, Witt sprays the
We topped the block with Air Flow Research (AFR) heads, which we received in CNC-finished form. We didn't want to make any major mods to the heads, since AFR has done a great job of designing and finishing them-we wanted to work with them as-is since they are so good out of the box. Thanks to Tony Mamo at AFR for his advice and guidance on our game plan. The heads ship with 240cc intake ports, 2.165-inch intake, and 1.60-inch exhaust valves, and they flow very well as-delivered. We felt we could determine the capabilities of the heads, and then build the rest of the engine around them to maximize efficiency. They were flowed on the in-house bench at TPIS (so all previous flow data and results accumulated on the same bench could be used for relative comparison) and the plan evolved from there.
Once we completed flow testing, we settled on the 383ci displacement level as one the heads were fully capable of feeding. Team leader Myron Cottrell says: "I wanted to keep displacement under control. It would have been easy to stroke the engine out to over 420 cubes and produce some big numbers, but we had to focus on efficiency here. The valves needed to be completely unshrouded, but it's easier to get horsepower-per-cubic inch efficiency from lower displacements, and we knew there would be a size limitation on the exhaust pipe diameter. This meant all the competitors would be breathing through the same diameter exhaust pipes, so a smaller displacement engine should have some advantage over a larger one breathing through the same pipe in this rpm range. [3,000-7,000 rpm-ed.] The 383 displacement would be able to make good torque, and with the single-plane intake manifolds we were considering, we knew it could make good power right up to the 7,000-rpm ceiling."
After the piston tops got their ceramic coating, the piston skirts got a graphite-based co
The TPIS team also knew they'd be running the ultrastable race-proven Jesel 1.7:1 rocker assemblies. We shared our airflow and target displacement figures with Cam Motion and also with COMP Cams, and respectfully accepted their input and suggestions on potential profiles to test. Four camshafts were soon on their way to the shop.
The intake manifold was the next major component to choose. We considered all the factory-type (front-fed) and traditional (top-fed four-barrel type) intakes that were commercially available and legal for use in the competition. We decided that the four-barrel style would be best, and ended up testing several different types before settling on the Edelbrock Super Victor. We learned that the longer the runners were, the greater the power and torque potential existed in the
target EMC rpm range of 3,000-7,000 rpm. This greater-length theory extended right up into the throttle body, as our testing showed greater returns from taller examples. TPIS manufactures several different throttle bodies for use in these configurations (mounted like four-barrel carbs on EFI applications) and the tallest one delivered the best results. In fact, the 102mm "tall" TPIS throttle body was some 20 lb-ft better in testing than a standard-height unit (up to 5,000 rpm).
We also tested a wide range of exhaust headers. TPIS manufactures several excellent long-tube designs that we felt would work well in the Challenge competition, including their late-model Pontiac GTO and Cadillac CTS-V offerings in stainless steel. Previous testing had shown them to be great performers over a wide rpm range, but a check into the EMC rules showed the previous callout for a chassis assignment for the headers was no longer required. This opened the door to other designs, and we acquired a couple sets of headers from American Racing Headers to test. This proved to be a good move, as we found power in American Racing's 1.750-inch/1.825-inch stepped diameter, 26-inch-long primary pipe Corvette headers with 18-inch-long collectors.
Speaking of rings, here are the trick Total Seal .032-inch low-friction competition parts.
The 3.625-inch stroke Callies crank is not only beautiful, but carries minimal weight too.
A close-up peek at the crank shows the counterweights, the oil shedding coating (to help k