It’s about trends, but engine building changes and one has to keep up with that. I have a blind spot there.
For example, I don’t care what you do for cam timing and exhaust and intake tuning there is no way you can take 400 plus inches and shove it through a 1.600 exhaust valve and not have what I consider a ton of exhaust duration.
And that includes killing the r/s ratio, regardless of what the rod length doesn’t matter crowd says. It does matter (actually it’s not the length of the rod that matters but rather the ratio of the length of the rod relative to the stroke).
To that end, you need math that considers bore and stroke, bore/stroke ratio, rod/stroke ratio and other seemingly minute details.
If you go to
speedtalk.com and go to the engine forum you’ll see at the top of the page there is a post that says a few Horsepower Chain books left. It’s worth every penny.
You can use that math and it will get you real close. Closer than anything else I’ve found.
