Thread: Getting more power out of a 307

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I like your ingenuity! If you can’t find aluminum heads - there are a couple of cast iron 305 heads that will give you an instant boost in performance due to their smaller combustion chamber size. If you can find either 14022601 or 14014416 you’ll have a winner. The 416 heads are 58cc and were used on the ‘80-‘81 Z28 Camaros and all have 1.84” intakes. The 601 heads have a 53cc chamber and were more widely used, but only the Z28 SS Monte Carlo and police car engines had the 1.84” valves for sure – all others typically had 1.72”. Both casting numbers have 1.5” exhaust. The 601 is the best if you can find a set with 1.84” intakes.

Make sure to have a good valve job and check for cracks. Hot tanked and cleaned up they should look like this. They flow pretty well as they are and within your budget; I wouldn’t expect a machinist to get fancy with any porting or polishing. Some light work with a die grinder to match intake gaskets is probably a good idea if you feel confident in this – otherwise don’t do it as too much material removed will hurt your overall performance.

This along with Rumrumm’s manifold suggestions will definitely give the 307 a bit more punch.

Have fun,
Glenn