Scottj-Interesting thread we got going here , ya think? Don't know Don Terrill is but I will pickup his book. Don't think I will agree with much he has to say though or in the very least it may recap what I " think " I know. I'll see.
The weight of the rotatating assembly on the bottom end is but a one factor that determines how a engine accelerates a car. I've seen it repeated over and over again and this is the #1 oversimplification I see when guys want engines built. The overwhelming limiting factor to how a engine revs is the valvetrain or the topside of the engine. Other factors play limited roles like rod angles, friction reducing coatings, non skirted pistons, dykes rings, head port design and so on.
The top end problem is what has doomed the Chrysler hemi (old style) to a non competitive status in the last few years with gas engines. Valvetrain was just to complcated. Carried to the other extreme, why do formula engines rev to 17,000 rpms almost instantly? Because they don't have a valvetrain resisting rotation that's why.
Now , back to the bottom end. I've seen dirt cars (true mad dogs) engines with bottom ends so light that they actually slow down a car going into a corner. This is because a engines internal friction slows the car with no resip. weight to keep revs up when they let off the gas. There is a balance point here for performance on bottom end rotating weight. Another thing most guys don't know, Cup engine builders build engines to the lenth of the track and turn lenths. The same thing happens for drag guys to. To light and the car will not launch, to heavy and it slows down the big end R's. Back to the big block heavier crank weights- it's really a small cog in a very big wheel.
As for the cup guys engines, I haven't seen the rules they go by for a couple of years now. But back then they mandated types of rods,pistons and crank weights. All this stuff added rotating mass. We really had (or have?) much better aftermarket parts availible we can use on our "street" hot rods.
Bandit1- I am a big block guy. But when it comes to lightening up a car anything a big block guy can do, a small block guy can do to.
As for how big blocks run, I like the way you can get on them in any gear from any kick point. Small engine guys have to shift.
cobrashock
