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GT40 Rebuild |
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Gonne929 
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Joined: July-08-2006 Location: Framingham, MA Status: Offline Points: 55 |
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 Topic: GT40 RebuildPosted: June-02-2021 at 2:16pm |
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Hey Everybody, I’ve been one of those members that hasn’t posted over the years but you all have helped me troubleshoot GT40 gremlins by reading others posts. Thank you!
Here is my issue... my GT40 has 1450hrs and will most likely need a rebuild soon. I’m looking into using a local machine shop to machine block/heads BUT as an alternative... Has anyone purchased any long or short blocks? Long block preferred. Any recommendations? If a short block any recommendations on replacement heads? Just trying to weigh my options. Thanks everyone for your help over the years. |
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Gary S
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Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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Posted: June-02-2021 at 4:04pm |
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Nobody does major surgery without tests first. Have the oil tested by someone like Blackstone. Then do cylinder leak down. Who knows maybe you only need valve work. Depends on how deep the pockets are but with the prices of new and even used boats are lately does not look like a down side. I took one in to have the block machined and the rods and crank checked almost 2 years ago now. Since I wanted minimal bore increase he did say parts were not as easy to get as had been in the past. Would liked to have only gone .010 over had to settle at .020
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slmskrs
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Joined: January-03-2012 Location: SF bay area, CA Status: Offline Points: 522 |
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Posted: June-02-2021 at 5:26pm |
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I had head water jacket leaks around 1100hrs so replaced them with GT40W on my '96.
My '97 with about 1100hrs has low compression in one cylinder (and putting oil in the cylinder doesn't change it, so it is a valve issue). I'll probably replace the heads on this one as well. I sold my '96 with 1600 hours on it and it was extremely strong; since I was anal about maintenance, I expect the '96 will go 3000hrs without a rebuild (bought the boat new). The '97 is a project boat that I got 2.5 years ago and while it runs fine, it lopes a little at idle. I knew the compression was down a bit, but it was lower than I expected when I tested it recently.
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Gordon '97 Ski Nautique, GT40
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MrMcD
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Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3667 |
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Posted: June-06-2021 at 2:05pm |
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I put new heads on my 78 Nautique at 1100 hours due to low compression in one cylinder. Had one burnt valve. With the new heads I ran it to 1500 hours and it was still running like new when sold.
The 351W GT40 is just a regular Ford 351W, straight forward rebuild. If yours was treated well for 1400 hours it may still have another 1500 hours in it. Compression Test, leak Down test can verify what condition your block is in.
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