Originally Posted by
omgwtfbbq!
The weight difference would be maybe a couple of pounds, completely negligible. You add 3 cams but you lose all the pushrods and rocker arms. The CG would likewise not be shifted more than a few ten thousandths of an inch, which is again negligible and could be accounted for by changing the oil tank design or something equally as trivial. The engine wouldn't need to be physically larger at all. If the cams called for more valve cover clearance you could easily shorten other components to account for that, if you shortened the stroke you could rev even higher. Audi's V8 engines fit between the radiator and front axle, just as my V6 sits entirely in front of the front axle. They sit the 4.2 in the R8, and even get the 5.2 V10 from the gallardo and the V12 TDI engines to fit without any issue. I don't know why you think DOHC engines are all huge. It would make more power because it could flow more air and that flow is more efficient. Bam.
Is this a joke? Fully assembled LS1 heads weight 25lbs. My B234F head weights 65! Unless DOHC valves are moved magically, there will be buckets or rockers and lifters, and twice as many. Half of a pushrod lives below the block deck, further reducing CG. DOHC motors put the weight at the worst part of the motor.
It would never be a "couple of thousands of an inch" that is just laughable.
I tell you what, measure the 4.2 width valve cover to VC, I'll do the same to my LS1. I'm happy they fit the 4.2 in so many places, but how much power does it make?
Cadillac's DOHC motors fit in the corvette's engine bay, except for they only displace 4.6L and make shitty comparable power. Not even supercharged do they approach LS7 horsepower levels. The Corvette is the perfect example of why OHV's still have their application.
"Efficency" is like ricer math HP/Liter. Garbage. The only factor that practically matters when weighed against power output is weight, hmmmm power to weight ratio. And by the way, the LS7 heads flow 360 CFM, no DOHC need there.