'76 302 Questions
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=22137
Printed Date: May-12-2024 at 9:18pm
Topic: '76 302 Questions
Posted By: 87jct90
Subject: '76 302 Questions
Date Posted: June-16-2011 at 5:52pm
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I just have some questions about the 302 in my 1976 Ski Tique.
1) I have an opportunity to buy a pair of gt40p heads from a buddy of mine if I pull them off his 99 Explorer. I can have them basically for free, will they bolt directly onto my '76 302 and if they do is it worth while to do? From what I understand, the gt40p heads are from a truck so it should deliver enough torque and bottom end power for my '76 Tique. I just don't know if bolt patterns changed for the manifolds or for the head bolts. 2) What should my '76 302 rev up to while driving under power, or what is it capable of doing. 3) What spark plugs should I use for my 302, everyone keeps giving me #26 Autolites but the boat has #24 Autolites. 4) What would my 302 be considered, it is a truck motor or an industrial motor? ------------- "It's not the destination, it's the journey." |
Replies:
Posted By: TRBenj
Date Posted: June-16-2011 at 5:59pm
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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. ------------- |
Posted By: 87jct90
Date Posted: June-16-2011 at 6:01pm
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I forgot, I had another quick question, what is the stock compression on my 302, is it a low compression motor like the 302s at that time or is it higher because it is in a marine application. If I do swap the heads does anyone know what the compression will be changed to? ------------- "It's not the destination, it's the journey." |
Posted By: TRBenj
Date Posted: June-16-2011 at 6:09pm
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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. ------------- |
Posted By: 87jct90
Date Posted: June-16-2011 at 6:15pm
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I really cant thank you enough for your help, so it sounds like I should do the swap, I was looking at the other posts on the subject of the gt40p heads and everyone was saying to also upgrade the cam and intake. I searched the subjects but nothing came up for my application. Do you have any suggestions on what cam or intake would pair up nicely with the new heads? ------------- "It's not the destination, it's the journey." |
Posted By: TRBenj
Date Posted: June-16-2011 at 6:30pm
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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 http://www.camresearchcorp.com/ - 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. ------------- |
Posted By: 87jct90
Date Posted: June-16-2011 at 6:57pm
Thanks for all the advice, I am going to call my buddy and start to take those heads off. I have zero clearance under my box for a higher intake (the bolt holding my air filter down has made a nice hole in my engine cover). I was looking up the intakes and cams, I might swap out the intake but I think I might skip the cam for now, its getting a little pricey. I really had no plans, I just have the opportunity to grab a pair of heads for basically free. I would hate to lose the opportunity to upgrade my motor when I have the opportunity. I know the motor has been rebuilt in the mid 90's, I do not even know what cam is in there. It has a slight chop to it already so I think it is a better than stock cam already. Now that I think about it the intake might have been upgraded already also if it is hitting the engine cover. I will have to go look  ------------- "It's not the destination, it's the journey." |
Posted By: kapla
Date Posted: June-16-2011 at 7:02pm
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On the bolts you are fine if you have the 302, they will require no mods...exhaust patern should also be the same...
------------- <a href="">1992 ski nautique |
Posted By: TRBenj
Date Posted: June-16-2011 at 7:05pm
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You should be able to find a used intake in the $80-120 range if you dont already have a warmed up one on there. A cam will set you back $250. For the amount it will cost you in gaskets and bolts alone to do the heads, its worthwhile to do it all at once- just something to consider. I would also replace the timing set ($40) while youre in that far. ------------- |