Replace bad GT40 heads with aluminum ones
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=33799
Printed Date: October-08-2024 at 1:16pm
Topic: Replace bad GT40 heads with aluminum ones
Posted By: the bull
Subject: Replace bad GT40 heads with aluminum ones
Date Posted: June-08-2014 at 1:24pm
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I have a 1996 Ski Nautique with a 351w pcm motor. My stock gt40 heads are testing bad (leakdown test shows air leaking into intake. I want to replace the heads and came across Ford Racing ones on summits website http://www.summitracing.com/parts/fms-m-6049-x306 They look like they fit right in! Anyone use these or have any input before I pull the trigger? Cheers Tommy |
Replies:
Posted By: Gary S
Date Posted: June-08-2014 at 2:42pm
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You could,I think Joe has aluminium ones on his stroker motor. Other than that if you use them on a stock engine you won't see any gain. Many,myself included have used GT40p heads with excellent results. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1711&sort=&pagenum=1&yrstart=1966&yrend=1970" rel="nofollow - 69 Mustang HM SS 95 Nautique Super Sport |
Posted By: the bull
Date Posted: June-08-2014 at 4:24pm
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I want to be able to run 87 Shell Marine gas with out any worries. Don't the p heads bump up the compression? The only 93 octane gas around here has ethanol in it. Is there a place that sells new p heads or do I have to gamble on a used set then take them to a machine shop and hope they do it right? If it runs good I am happy, just don't want to use something that is going to make me lose that low end torque that the boat is designed for. THX! Tommy |
Posted By: 8122pbrainard
Date Posted: June-08-2014 at 4:32pm
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Tommy, Tell us more. Why are you concerned with ethanol 87 fuel? Both straight gas and ethanol are still unleaded. ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: the bull
Date Posted: June-08-2014 at 5:07pm
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I do not use ethanol gas in my boat. It draws water in from the atmosphere from what I have seen and goes bad quicker. It tears up plastic and hoses as well. 87 marine gas works great in cars as well. I have seen it make cars with failing catalytic converters run cleaner. I also get better fuel economy in my cars with as well. |
Posted By: the bull
Date Posted: June-08-2014 at 5:08pm
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BTW 87 Shell Marine gas does NOT have ethanol in it. |
Posted By: Gary S
Date Posted: June-08-2014 at 6:36pm
Valid concerns Tommy however Pete and I live where it's easier to buy a hand gun on a corner than it is to buy gas with no ethanol  We have to run it in everything we own. The only engine I have had trouble is in a Stihl weed whip and I'm not even sure that was the cause. Keep in mind Ford had to design their heads for where ever they were used so they had to be for all 50 states. I personally would be more worried about dissimilar metals using plain water than running alcohol in the fuel and really that's not a problem in fresh water. The reason you get better mileage in a car with no ethanol is because ethanol has less btu's than gasoline. I have heard that is why you get better mileage with a top tier gasoline compared to a no name brand. A no name will sell for price and can use up to 10% ethanol where as a top tier might only have 5%. As to compression you will have to check out what the aluminum heads have for chamber volume,they too might raise it,but aluminum does disapate that heat better. I believe my low end with the p's is better now than with the early 70's heads I had. You can buy remanufactured heads. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1711&sort=&pagenum=1&yrstart=1966&yrend=1970" rel="nofollow - 69 Mustang HM SS 95 Nautique Super Sport |
Posted By: JPASS
Date Posted: June-08-2014 at 7:02pm
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Whats the price difference between the Ford Racing heads and GT40s? ------------- '92 Correctcraft Ski Nautique |
Posted By: 8122pbrainard
Date Posted: June-08-2014 at 8:46pm
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As Gary mentioned, I too would be concerned with dissimilar metals. Yes, it has been done but with the expansion rate being different there's always a chance it won't work out. Have the old ones worked on or as mentioned get a set of the GT40's ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: MrMcD
Date Posted: June-09-2014 at 12:21am
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Any good machine shop can repair your current heads to 100% new condition, you can ask around and find great shops in your area, NC is home of Nascar shops so many good shops are around. I would certainly use word of mouth on recommendations not local adds. Aluminum heads are not an issue and many times can give you better flow than factory heads. AFR would be my first choice if an upgrade is wanted but with our boats maxing at 5,200 RPM you may not realize all the potential a good Aluminum head can offer and at $400 for a rebuilt set of heads vs 1,800 for a set of good AFR heads you might want to consider what you really want. The GT40 runs really well factory stock. If you were spinning your engine to 6,000 RPM I think the power gap would be wider and the advantage of good heads would go up but at 5,200 I doubt if you would find 25 HP even in AFR design heads. |
Posted By: the bull
Date Posted: June-09-2014 at 6:44pm
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Yeah I hope they can fix the GT40 heads for me, but if they are cracked then they are boat anchors. The ford racing heads are almost the same specs as the stock heads. That is why I like them. Skidim has the gt40 heads but they are a little to proud of them for what they are asking. Where do you guys pick up reman heads(gt40p)from? |
Posted By: kapla
Date Posted: June-09-2014 at 7:12pm
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A good set of rebuilt gt40p's will run on the 500 or 600 range..bolt on ready... try either Tri state cylinder heads or Clear water cylinder heads... ------------- <a href="">1992 ski nautique |
Posted By: MrMcD
Date Posted: June-11-2014 at 11:27pm
| Check with your local machine shops, they may have cores sitting on the shelf. Many people upgrade to Aluminum heads for car applications and the old heads are set aside. You may find a spare easy if needed. |
Posted By: Tim D
Date Posted: June-12-2014 at 1:02am
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When you put it together, I recommend Fel-Pro gaskets. ------------- Tim D |