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Hey everyone ,
My 455 has some blow by from valve cover breathers so I did compression test and here are the Cylinder results.

8- 142psi 7- 97.1psi
6- 75.5psi 5- 36psi
4- 98psi 3- 41.2psi
2- 144psi 1- 142psi

I’m thinking blow head gasket and wanted some other opinions before tearing the top half apart to find out the rings are bad .
Is it possible I have a exhaust valve stuck or lifter issue.

Thanks to all who take the time to read my message .
 

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hmmmm
this is with the throttle open so it can draw in air when cranking ??
oil is clean ??
radiator coolant is ok ?
no lifter tick ?
any miss or back fire ?
how did the plugs look all the same color ? any black ones ,,, wet ones .,.. clean ones ??
 

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First, how did you do the test? It should have been with all 8 spark plugs removed and the throttle blocked wide open. If that's not how you did it, then do it that way. You'll get different results.

If you still have "low" cylinders, check those again immediately after squirting some oil in through the spark plug hole on those. If you get a noticeably higher reading after doing that, it indicates the problem is most likely ring seal. If not, then it's probably head gasket and/or valve/valve guide leakage.

Using a leak down tester is another good diagnostic tool. Always used with a warm engine, it can tell you how much a cylinder is leaking and also where from.

Bear
 
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