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looking for new heads for the gt40 |
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mjstonework122@hotma 
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Joined: April-04-2014 Location: United States Status: Offline Points: 29 |
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 Topic: looking for new heads for the gt40Posted: September-01-2022 at 9:07am |
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its a 2001 super air nautique I did a compression test and got 125 average except cylinder 5 and 4 on opposite ends and different sides. on those cylinders it had about 70 psi. I squirted in some oil to do a wet test and got 79psi on one cylinder and 70psi still on the other.
the boat took on water 2 years ago and i think it caused rust in those valves but that is just my theory.
it might also be having a problem with the ecm. do you guys think 125 psi on the other cylinders has enough life left to justify new heads? |
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MrMcD
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Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3590 |
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Posted: September-01-2022 at 1:52pm |
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I think you answered this question yourself, you have 2 dead holes, one on each bank. Your heads need to come off for repairs. Your oil test tells you the problem is in the valves but one more thing to check is the camshaft, make sure the 4 and 5 cylinders valves are opening and closing properly. If the 4 does not open valves as far as your #3 that would point to a flat camshaft lobe but you need to measure lift not just eyeball the lift. Most likely you need heads.
A read for getting good numbers with your compression test. https://www.correctcraftfan.com/forum/forum_posts.asp?TID=3966&KW=compression
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