School of Automotive Machinists 435ci Cleveland Ford Motor - Horsepower Evolution

As one of the premier performance engine tech schools in the country, the exercise of building an engine and competing in the Challenge presents a unique opportunity for the School of Automotive Machinists. Of course, the event is a proving ground for the collective talent of the organization, but more than that, competing allows students to gain direct hands-on experience in a highly competitive venue. As team leader and instructor Chris Bennett tells us: “It was 100 percent a class project; everything in it was overseen by myself and other instructors, but all of the critical parts of the engine were done by the students, from the machining to the assembly.”

The build started with a World Products Man O’ War iron block, configured with a long-stroke combination, featuring a bore of 4.065 inches and a 4.185-inch stroke. Bennett explains: “We wanted to get the piston speed up at lower rpm, so we went with the longer stroke. The goal was to get the air speed up in the manifold and decrease the reversion.” The components inside were selected with long-term durability and quality in mind. The custom Winberg crank features profiled counterweights and extra-small Honda-sized rod journals. Bulletproof Manley 6.000-inch rods with the corresponding 1.888-inch journal dimension complete the assembly. Commenting on the small journals, Chris says: “It cuts the surface area down, and it decreases friction. It also reduces the weight at the rod and the counterweight, and improves the crankcase clearance with the longer stoke.

Custom Wiseco pistons seal the bores, and these were built with several tricks. When the engine was built, gas ports were not legal in the class, however, the ring setup included an extra .030-inch spacer, which contain grooves that effectively mimic the use of lateral gas ports cut into the pistons. The ring package features very narrow-section .325/.325/2mm rings from Total Seal. Chris explained the reasoning behind the narrow rings: “The rings were another frictional reduction. The narrow rings conform to the cylinder better than a wider ring, however, the tune-up becomes more critical. When you have that thin of a ring, it can pinch the ring land a lot easier; the ring land becomes more delicate at that point.”

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.”

Another component that received extensive testing was the header. Here testing included everything from a “tri-Y” setup, differing lengths in the primary tubes, and several collector types. In terms of spotting trends, Chris tells us the changes were subtle: “The individual changes were so small that you would just look at the graphs and see where the power curve was affected, and then check the bottom line average power numbers. Often, the generally accepted theories did not pan out. For instance, we found a shorter primary made more power all the way down to 2,500 rpm, so we shortened them up. The primary tube size we used was 1⅞ inches all the way down to a 3-inch collector. On the collectors, the merge made more power everywhere than the open collector, and here the choke point of the collector proved to be a critical area.”

Much of the testing and subsequent modifications that went into developing this engine were prepared for the 2010 AMSOIL Engine Masters Challenge, however the team withdrew without running due to a failure of the oiling system. The oil pump would not prime to build pressure while cranking, and the team decided it wasn’t worth risking the possibility of destroying the engine. A chance for a reprieve came in the 2011 event, where the engine was mildly reworked to meet the rules, with the previous discussed combination. The SAM’s outstanding engine-building effort was validated as soon as the engine worked through its first set of qualifying pulls in the Street Division, taking First Place in qualifying, developing as much as 686 peak horsepower in the process. The point was driven home as the engine completed final eliminations to secure the Division Championship in Street. The success of the SAM engine in competition proves that building competitive horsepower is truly an ongoing process of development.

Ford 435ci Cleveland