vortecs are advertized as a 64cc head, however the pair that i have on the shelf for my IROC were measured out at close to 62cc's, thats what i go off of. As for the difference in compression with the 350, its true that the older 350s run the larger chambers, and that the vortecs will raise the compression more, id run the math but it depends on piston dish, yadda yadda and theres really no one answer on the ending compression. when i did my research i was looking at newer 350s in the camaro line, which run the smaller heads, so thanks for pointing that out for me as i missed it.
as for the 305 vortec combo, hotrod did that in a camaro, and to get decent compression, they had to machine the deck surface at an angle, and then correct the intake mating surface as well, to make the heads fit and get a compression ratio of i believe 9.6:1.
as for performance with the egr, semantics, poor word choice on my part, i was talking about how well the engine worked, and with the egr, it runs cooler, produces fewer emissions, and there isnt a loss of performance, which means your using less fuel and running more efficiently. although by running cooler you prevent detonation and depending on weather or not you have a knock sensor, it might actually provide better performance
I also agree that the fuel delivery system makes a big difference in fuel mileage, but i dont agree that you can so easily brush aside the effect of a more advanced combustion chamber design. the reason the vortec heads make so much more power than older heads is that they more efficiently burn the given air fuel mixture, more power for a given ammount of fuel means that you can use less fuel for the same power levels, which means in similar driving conditions, the engine that more efficiently burns its fuel, will get better mileage, simple thermodynamics. any time you make an engine produce more power without adding more air or fuel, it will produce better fuel consumption rates, as an example i give you the early ZO6 corvettes, that put out 405 hp, and get 30+ mpg on the highway. accomplished through combustion efficiency.
also, its not nessesary to modify the vortec heads for higher lift, a set of beehive springs from comp cams fits over the stock valve guides and allows up to .525in lift. i dont have the part numbers off the top of my head, but i can find em if nessesary. as for the engine not producing 480 hp on the stock heads, like i said, it depends on the variables, to take it to the extreme, are you saying a turbocharged sbc with vortecs wont make that power? i dont recall if it was said it was NA, but im just sayin, theres alot i didnt know, i just said it was believeable. never said you could bolt those heads on an otherwise stock engine and put out magic power levels.
as for the disclaimer, no worries mate, i raise a beer to ya, always nice to meet a fellow ass, i work at a shop, trust me im used to it
i dont claim to always be right, but i never speak unless ive done some sort of diggin into somethin, like i said, ive got a set of the heads on a shelf to go on my IROC, so before i put them on my car i researched the hell out of em, although admittadly its late, and im shootin off stuff from the top of my head rather than my notebooks, so if i get somethin crossed up, id rather be called out on it than lead someone astray. kinda one of the nice things about the forums
