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Low compression

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Rugdork

New member
I recently had the port side head rebuilt on my 2002 monterey 228ss with a 5.7L volvo penta F/I motor. *i am trying to sell the boat, it ran great after the head was installed. *I let the potential buyer bring it to his own mechanic to look at it, The mechanic put it on the computer and found the following, 1-85,2-170,3-145,4-190,5-150,6-190,7-175,8-195. *Everything else checked out good. *It is weird to me that the compression is so scattered and knowing the valves were pitted on 1,3 and were not seating causing the low compression prior to the rebuild. *I am not confident that this mechanic was right so I did take the boat out ran it for about 45min up and down in RPM's and retook the compression on 1 which was 135, and 2 which was 145. *Is there a break in time for a rebuilt head? *The boat seeemed to run like it used to all the way up to 4700Rpm, it died once at idle after running it but I feel there is bad gas in it, prior to all this mess the boat has sat since last july and talking to other people the low compression could be caused by maybe crap that needed to burn out to help the rings break loose? I'm at a loss, I am going to recheck all the cylinders tomorrow for compression and see what it is at, any suggestions, ideas, thoughts? *I really would like to sell this boat, other than all this it is in excellent shape. *Thanks for your input*
Doug
 
No, there should not be any "break-in" time for a new cylinder head.

You mention "head", as in one cylinder head was replaced.... is that correct?

Are you familiar the SBC cylinder numbering?
Port side bank will be 1, 3, 5 and 7....
Stbd side bank will be 2, 4, 6 and 8....
(opposite for V-drives)

Here are your numbers:
1-85, 2-170, 3-145, 4-190, 5-150, 6-190, 7-175, 8-195.
With your high pressure readings, is it possible that these are actually all on the Stbd side (2, 4, 6 and 8)?

I ask this because if the wrong cylinder head was installed (spelled smaller combustion chambers) it may explain the higher readings, but again, only if these are all on one bank!
There is one caveat to this; by 2002 the chamber volume would have been 65cc.
(65cc is a small chamber, therefor an error in the direction of a larger chamber, would reduce cylinder pressures.... not increase them)

Are you cycling each cylinder 4 or so times, and with throttle plates open, for each pressure reading?

.
 
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