An OHC motor is taller than a pushrod motor obviously due to the valve train on top of the cylinder head(s) vs. being buried in the block. As I understand it, that was one of the reasons given for not using the Northstar in the Vette.
no, it's not. the vette needs to be powered by a small block to be marketable. that means a two valve head, that means a lot of torque low down and a certain exhaust note - the torque requirements put displacement, bore and stroke into a certain range (as do marketing aims), the exhaust note arguably is the only thing LS1 screwed up on release.
An OHC motor also makes more noise than a pushrod motor for the same reason as above. That's why you see luxury cars with shrouds over the top of the motor, also adding to height.
no, it makes different noise to a pushrod motor, with more high frequency noise. unless you're running a geared valvetrain, valvetrain related noise is a small part of engine acoustics regardless.
Speaking of the Northstar. As I understand it, this motor is undersquare, that is the stroke is longer than the bore diameter. Given that the bore to displacement ratio is lower, the available bore diameter into which fit valves is lower, driving the need for multiple valves. When introduced into the IRL, the rev limit was originally set at a point where an IRL motor had a max piston speed higher than an F1 motor at that time. (and they ran it for 500 miles at near peak revs.) There was a lot of spectacular blow-ups. They eventually lowered the rev limiter, which was followed by a reduction in displacement, followed by non production parts, etc. etc.
the relevance to the whole two/four/multi valve argument is?
his is the first time I've ever heard the ZR-1 motor described as a dog. If you'll think back, this motor raised the bar for US iron. They may not have pushed it as far as they could because they didn't have to.
is the first time i've head the zr1 motor referred to as a dog. it's clealy not.
two valve heads as a technology isn't ---. it just has it's limits as does any other.
Finally, I find it darn impressive that the NASCAR boys are now routinely spinning a pushrod motor north of 9000 rpm for 500 miles with a flat tappet cam. Holy Smokes.... Imagine if they were allowed a roller cam.
NASCAR is more impressive in that it offers a high degree of entertainment and relevace for the fans, a high degree of competitiveness for those involved all at a moderate cost to go racing.
doesn't really matter what's restricted or used under the bonnet so long as everyone's in with a relative shot on race day and the fans know it.
the engines involved are
dinosaurs by modern standards but the racing can teach more technologically evolved racing formulas a hell of a lot.