The headers on Jon Kaase’s 409ci Mod motor that won the 2013 Amsoil Engine Masters Competition probably drew more attention than the final horsepower numbers. A multi-time winner of the Engine Masters, Kaase took advantage of a change in rules that allowed 4-valve engines and built up a fresh entry based on a 2000 Cobra R platform. Since the rules emphasize a broad torque and horsepower range — not just peak numbers — Kaase developed a unique header arrangement to twist as much torque as possible in the lower rpm range. EngineLabs caught up with Kaase at the PRI Show and asked for more details.
“With the Engine Masters, the exhaust is so important because the engine spends more its time below peak torque than above it,” explains Kaase. “Once you get to peak torque and above, you can change a lot of things — and it really doesn’t change the power much. When you get to peak torque, it’s pretty efficient. You could change the header 10 inches and it barely shows, but down low it makes a big difference.”
Kaase started with a Ford Motorsport block and resleeved it to handle a 3.720-inch bore. He then threw in a 4.700-inch stroke crank to get past the 400ci minimum for the competition.
“I put as much stroke as ever been put in [Ford Modular engine],’ says Kaase. “The big stroke does help the low-end power. Usually if you have a small bore it hurts the breathing of the head, but it’s a 4-valve. The icing on the cake is that the 4-valve doesn’t need much camshaft — about 20 degrees smaller than 2-valve. And when you use a smaller cam it helps the bottom end, too.”
The headers were inspired by a set of exhaust pipes Kaase saw on a custom Buell motorcycle built by Brian Fuller.
“I saw four exhaust pipes and thought it was a V4,” remembers Kaase, who uponn closer inspection noticed it was one pipe for each exhaust valve, and those two pipes met in a Y. “That got me to thinking about it.
“There’s a 4,000-rpm spread in the competition,” continues Kaase. “At some point you’re on the wrong side of the header wave. The pulse is likely working against you because it’s arriving at the wrong time when it comes back up the pipe.”
At first, Kaase tried a long and short primary tube for each cylinder.
“It’s all trial and error. I had one collector here, and then way back there, and then 4-into-1 collectors” he says, pointing all around the engine. “It was okay at peak torque and above but down low it was terrible.”
Kaase started shortening up the pipes with two collectors, then he attempted a Tri-Y design that started boosting the low-end numbers.
“But it still had a hole in the torque curve where if you drew it out there would be a sag around 3,600 rpm,” says Kaase.
Kaase then made extensions between the two sets of Ys. He might have gone longer but there were limitations due to the size of the dyno cell.
Sharp-eyed observers will note that the header arrangements are different for each side of the engine.
“The reason is the firing order,” explains Kaase. “You don’t want two cylinders firing back-to-back in the same group.”
In the first round of competition, Kaase’s engine hit 720 horsepower and 666 lb-ft torque. In the final round, peak numbers were 721 horsepower with 675 lb-ft. But again, the focus was on broad torque numbers.
“Those headers really did help us score down low and we really didn’t give up anything up high,” says Kaase. “At one point it made 630 lb-ft at 3,200 rpm. That’s a lot of torque at 3,200 for a 409-cubic-inch engine.”