Compression Test!!!

[frostywalrus81]

Hey guys I have a 1971 Mark Twain w/ a 165hp Mercruiser Inline6. I ran a compression test on the block today and I am not sure if my numbers are good or not. I couldn't do the test with a warm motor cause it doesn't idle very good right now. The numbers I came up with were:

1 - 105
2 - 130
3 - 125
4 - 127
5 - 130
6 - 112

Please give me some advice as to if these numbers are good and if not then what the problem might be. Thanks

 

[windsors03cobra]

Re: Compression Test!!!

Your in OK shape, you have a used 30 year old engine. Should run OK.

 

[APPALOOSA2]

Re: Compression Test!!!

Compression on the 165 GM 250 new is 140 psi.
Like Windsor said your fine just a litlle tired a valve job would probably bring her back.

 

[JustJason]

Re: Compression Test!!!

Try doing a valve adjustment and see if you get a few pounds back. All the numbers are on the lower side, especially that number 1. But with any compresssion test the magic number you need to have is 100+ psi. Typically anything under 100 is considered non servicable.