Will Chevy 307 heads fit on a 305?

Yes, Chevy 307 heads will generally fit on a Chevy 305 block. Both engines are small-block Chevrolets and share the same bolt pattern. However, there might be some minor differences that require attention:

* Valve size and combustion chamber volume: The 307 heads may have slightly different valve sizes and combustion chamber volumes than the original 305 heads. This can affect compression ratio and performance. You might need to adjust your engine tuning (carburation or fuel injection) to compensate.

* Exhaust porting: The exhaust porting might not be perfectly matched, leading to minor performance variations.

* Accessories: While the heads themselves fit, the accessory bolt patterns (for things like the intake manifold) *should* be the same, but double-checking is always advisable.

In summary, while physically fitting is possible, you'll want to be aware of the potential performance and tuning implications before swapping heads. It's not a drop-in, guaranteed-perfect swap. Consider consulting a mechanic or engine builder experienced with small-block Chevy engines if you're unsure.