Some of you might remember that I rebuilt my motor from scratch about 2 years ago and I have about 1500-2000 miles on it since. Jakes 383 rebuild I did a compression test this weekend for shits and giggles and the every cylinder was at 118-120 except #6, which was at 60. My heart dropped. Someone, please tell me this is in the valves and not the cylinders!!! She runs like a bat out of hell, little slow of the line but she is 4500lbs.
60 psi on #6
- Thread starter jake
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67Monaco
Go Woke, Go Broke.
What does a wet test produce?
And was this hot or cold?
Did you verify the rockers are opening?
On a build this low on milage i'd suspect maybe a wiped cam lobe before ring issue.
Also make sure the compression tester is tight. Had that problem myself when #1 was 90psi and the rest were 150. Went back and rechecked and tightened everthing up and numbers went where they should have been.
Dont freak yet.
And was this hot or cold?
Did you verify the rockers are opening?
On a build this low on milage i'd suspect maybe a wiped cam lobe before ring issue.
Also make sure the compression tester is tight. Had that problem myself when #1 was 90psi and the rest were 150. Went back and rechecked and tightened everthing up and numbers went where they should have been.
Dont freak yet.
Do a second compression test after adding about 3 oz. Of oil through the spark plug hole. Attach your compression gauge and retest. Low or little change more than likely a valve stuck open or valve train failure.
Also, are you getting any valve train noise? A flat cam lob or bent push rod will produce low compression on the affected cylinder. Might want to pull the valve cover and check to see if both valves on #6 are opening and closing the full length. It is pretty unlikely that a 2k engine would have burnt a valve unless the machine shop screwed up big time fitting a hard seat or grinding the valves. Bent push rods on mopar big blocks that spend a lot of time sitting are fairly common so start there.
Dave
Dave
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I am the machine shop, thats what is worring me. I will pull the valve cover this coming weekend and see whats up.
Ok, I pulled valve cover and took of rocker arm, valves can be moved by hand, so they are not stuck. Pushrods are straight, not bent. I took video of the rocker arms in motion and the lift looks good, I did not mic it, just visual. Take a look and let me know what you think. Oh, did a wet test on that cylinder and it did not come up pass 60. BTW, test all been done cold.
rags
Senior Member
take the rockers off and put some shop air in through the spark plug hole using a hose from a compression tester. you'll find out if and where your compression leak is.
67Monaco
Go Woke, Go Broke.
Yup was going to suggest leakdown next. Pray for a bad head gasket.
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