ok new dart block comin pump gas motor street some nos maybe 496 540 or 572 ? wich one and why . ? is the 572 all that great over the 496 540 .? maximum performance street and strip break your neck power . oval vs rectangle. 345 355 325 370 intake runners.

Too many questions with too many variables.

Let's make this simpler: how much do you have to spend? How rowdy an engine can you live with?

Plenty of people have made serious low 10 second Chevelles with more garden variety 454's. What you usually gain with larger cubes for any given power level is a more well mannered engine. I.E., you can have a mellower 572 that equals the performance of a wilder 454.

The oval vs rectangle debate will go on forever, but more big cube engines seem to wear rectangle port heads. Yet, some of the newer big port heads have oval or roval shaped ports. The bigger the intake port volume the slower the velocity (which is not always a bad thing). Conversely, the bigger the cubes, the easier it is for a given engine to swallow a bigger port size. Same with camshafts - big cubes love lift and duration. The current solid roller in my 496 (not yet with track times) measures out with a net lift of .675 intake and .700 exhaust with 251/254 duration @ .050 lift installed straight up on a 110 center - idles great and can be driven anywhere.

Thomas

wow most big cube motors perfer 112 lobe sep or bigger

yes big motors likerectangle heads so as to get plenty of fuel and air . alot of guys starve them with oval,s . and it dosent seem like the 572 at 9.5 compression makes as much power as a 496 or 540 . gm lists that 572 at 600 hp i have seen 496 and 540 crates at 700 plus with 9.5 comp . seems like the 572 is odd ball power for some reason i mean no replacement for displacement but the 572 hasnt shown me much on paper anyways

Well, not so fast there - do you realize that the "paper" comparissons you are doing reflect vastly different dyno correction factors? Plus GM has a good business reason to be conservative with the advertised horsepower.

The SAE standard that GM uses is: 29.32 barometric pressure at 1,000 feet altitude with 77 degree air temperature. The popular standard temperature and pressure that the aftermarket corrects to is: 29.92 barometric pressure at 0 feet altitude with 60 degree air temperature.

Big BIG difference in those correction factors. Tell me what effect that you think cooler and denser air will have on power?

There is actually more to it than that - but this would be yet another reason why we don't race dynos. Or the printouts that come from them either. Show me the time slip - then we have something.

The dyno will always be a great tuning tool to hold everything as repeatable as possible.

Thomas