Weingartner 407ci Small-Block Chevy - Teacher’s Pet

Weingartner designed his ports with the goal to have relatively high average airflow velocity, without any tight pinch points that would choke it. He was able to do this by raising the runners and making them fairly wide, but not too tall. “They’re something like 1.37 inches wide by 1.880 tall.” Almost the exact opposite of a cathedral-port LS head. “I tried doing it tall and thin, like 1.228 wide and carrying it all the way through and like 2.200 high but it always liked it wider and shorter than taller and narrower. Kinda goes against that LS thing.” The only downfall to this design was the requirement to use offset lifters and rocker arms.

One of the things he really liked about the Brodix heads was that they had a big, deep bowl area under the valve. A theory that many head porters share is that the deep bowl lets the cylinder get a first big gulp of air as the valve is opening and velocity is building up in the runner. As the intake valve is just starting to open, there is a critical time when the exhaust valve is still slightly open (overlap is just starting) and the pressure remaining in the combustion chamber can be higher than in the intake runner. What that means is some of that exhaust can go up the intake tract (reversion). Not a good thing as it contaminates the nice, clean air in the intake manifold with nasty exhaust. After a few crankshaft degrees of this, the mass and sound pressure waves of the exhaust begin to pull the intake air back down into the chamber (scavenging). So what do we learn from this session? Class? Class? Anyone? Bueller? We want to hurt low-lift reverse intake flow, and we want higher lift flow to be good. One way to do this, which is what Weingartner did, is to use a 50-degree intake valve job angle. A large throat diameter, 91 percent of the intake valve in this case, also helps out.

On the exhaust side, Weingartner ran a traditional 45-degree valve job. This tends to work well with short-duration cams as they open late in the cycle. Opening late is good for holding the pressure of combustion in as long as possible, but they still need to get the exhaust out as quickly as possible once they do crack open. In other words, high low-lift flow numbers are good for exhaust in this case. It seems anathema (trying to impress the teacher here with big words) to want to open the exhaust valve while the piston is still going down on the combustion stroke. It is important to remember though that if we wait until the piston starts coming up before opening the valve, the piston will have to push all that exhaust out. Pushing means pumping losses. The goal then is to balance how much you are going to gain in reducing pumping losses against how much you are going to lose by opening the exhaust valve while combustion is still pushing the piston down. A tight balancing act.

When deciding how to balance that tightrope, Weingartner called Chris Mays at COMP Cams for input on the bumpstick. “The cam specs were 243/247 [intake/exhaust] on a 104 lobe separation with the TK lobes for high rocker ratios. The lobe itself is tiny, ’cause it’s a 1.85 rocker to get that .650-inch lift [max per EMC rules]. But it’s pretty damn aggressive.” The tight lobe separation was picked to get the most benefit from that overlap scavenging and to be able to place the valve opening and closing points where they would work for the best average torque and horsepower. The downfall of running it tight is that it kills the manifold vacuum signal at low rpm and idle so it is tough to run like that with power brakes or any vacuum-operated accessories in a street car.

Though the engine was destined for his own car (look for an update on quarter-mile performance) this beast first had to go back to school. To the University of Northwestern Ohio (UNOH) that is, where the Engine Masters Challenge was held. A virtually unlimited supply of eager young students was on hand to hook Weingartner’s engine to one of UNOH’s DTS/SuperFlow engine dynos. A fresh tank of VP100 fuel was set up to feed the engine and they threw 12 V to his trusty PerTronix ignition system to bring the engine to life. Poor Weingartner looked as nervous as a young boy sent to the principal’s office, but everything changed when the dyno operator hit the GO button, and she fired up. Weingartner jumped out of his seat and screamed “Hell yeah!” Everyone laughed, but he didn’t care if it made 1 hp or 1,000. He met his goal. The schoolteacher from Oklahoma stood up there with the engine that he built and just smiled as big as the plains when he saw that dyno needle climb to a staggering 616 hp. He’d done it all right. Now he really had something to brag about come “show and tell.”