'76 302 Questions

1) Search this site for "gt40p". These are a common head upgrade here. Besides the better flow, you also get a compression ratio increase.

2) It all depends on the prop. If running the original 12x14 Federal, then you should be seeing ~4400rpm. If youve got a different prop, then that may vary somewhat. For example, I would expect an Acme 1210 (12.5x12) to turn in the 4500-4700 range.

3) On the stock heads, the Autolite 24's are the correct plugs. If you go to GT40p's, those take Autolite 764's.

4) I suppose in this application it would be a marine engine.    The marine long blocks are very similar, if not exactly the same as their industrial counterparts.


FYI, there is absolutely no reason to every try and boost "low end power and torque" on these boats. Theyre pretty well detuned from the factory, which makes them very strong on the low end of the RPM range. When making engine upgrades, you would have to be trying extremely hard to pick wild or mismatched components in order to hurt your low end power. Picking components that improve mid range and high end power (like the P heads, etc) will often give the added benefit of improved holeshot as well.

If youre mainly concerned with holeshot, and often run heavily loaded (ballast, etc) then the best way to improve your performance is to go with a prop with less pitch- or one with more blade surface area (or both). Going with a shorter prop may have the undesired effect of decreasing your top speed, though.

On the compression ratio, take a look at the PCM manual in the reference section. I know the 351 has a low (8.3-8.5:1) CR, and I would expect the 302 to be similar. Going to P heads (which have smaller chambers) should get you into the 9-9.5:1 range.

First of all, what are your goals for the boat? If youre after more power, then doing the entire top end (heads/cam/intake) at once makes a lot of sense. The heads alone are the biggest part of the puzzle, though.

If you can fit it under the motorbox, a Performer RPM or Weiand Stealth intake would be the best choice. Otherwise, the standard Performer is better than stock. For the cam, call Cam Research and they'll set you up with a nice cam. Remember that you have a reverse rotation engine. They tend to be a little conservative with their ski boat recommendations, so feel free to get confirmation on what you want here before pulling the trigger.

I would also have those heads refurbished before bolting them on.

On the bolts you are fine if you have the 302, they will require no mods...exhaust patern should also be the same...