Sgruenauer96

I currently have the 7a heads, not trying to make crazy power but I want to pep up the engine a bit. Already have a holley street dominator intake, hei distributor, and a holley carb. Soon to get some headers, probably just some block huggers so they fit. I've heard the 5a heads will open wake it up a little. Are there any other cost effective options? If I port and polish up some 5a heads I'd assume I'd be pretty decent. I'd throw a cam at it knowing the 5a are Rollers not flat tappet. Any other ideas are appreciated. I'm no expert, I'm learning still, but I pick things up pretty quick.

olds 307 and 403

For one, you have a 85 and up roller cam 307, unless the heads were changed. I wouldn't throw a Street Dominator on a stock 307, losing any low end torque is all a stock 307 has going for it. Unless you mill those 5A heads enough to raise compression and add a mild roller cam, you will make it slower and less fun.

BillK

Like olds 307 said, you need to verify exactly what engine you have before you do anything. What year and model is the car ?

Sgruenauer96

Eh sounds like I'm buying a 350 on the weekend

brownbomber77

Yeah, just not really worth trying to make a 307 fast. At best, without breaking the bank, 1.875/1.625 are the largest valves you can stick in them. Valve spring upgrade, roller rockers (Ford pedestal mount are an affordable option), cut them .030 (any head you replace should cut this much to make up for the thicker head gaskets).

350, just make sure it's made before '76. Nodular crank, solid main web block. Heads you'll want made before 1972. If you're feeling like looking for heads, #3 and #4 330 heads should have a smaller combustion chamber than any 350 head. Any 350 will make more power than that 307 can reasonably make.