So Im looking to rebuild my 305 and get a little more performance out of it. WOuld I lose something by using 210cc heads (for like 350-400sb's) instead of something smaller. I dont see why all i can see gaining is more flow with the bigger valves. ANd i figure if i got more high comp pistons i would end up with near stock compression and great flowing heads/intake/exhaust. Am i missing something?

Yes. Skip the 305 and go straight to the 350. Mileage will be almost exactly the same and then you don't have to deal with the 305's small bore, which limits your head choices.

If by 210cc you mean the intake runner size, that's way to big for a mild 305.

Putting 210's on a 305 would kill the bottom end.

+1 on the 350.

If you are going to stick with the 305, dart makes a 305 specific head that is an improvement over stock.

Putting 210's on a 305 would kill the bottom end.

+1 on the 350.

+2 on the 350

Yes go 350 and if you want to tow or even drive it, stay less than 200cc intake runners. The heads you are looking at are race heads. Bigger is not better in this case for what you are doing. Run a mild cam with a set of decent heads.

If you want to upgrade the 305 with better heads, get World Products SR 305 torquers. they have a 58cc chamber and will give the 305 a little gitty-up. But the 305 in general is the worst bore/stroke combo GM ever did.. Hell, just find a good 350 block. All your parts, including crank, will work.

If you are TBI, you will have to upgrade the TB injectors from a 350 though. The PCM will still run a 350 too.

I used to do this stuff everyday.

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