[AT] Compression values and range

[charlie hill]

Dean the 90 psi reading could be something as bad as a broken compression 
ring but more likely something as simple as carbon build up on a valve seat. 
Once you get her running again try working her pretty hard for a while then 
a treatment of something like Marvel Mystery Oil, some more hard work and 
test it again.
Generally if all of the compression readings are within a 10% range you are 
ok.  Yours is a little off from that but not a critical failure reading.

Charlie
----- Original Message ----- 
From: "Dean Vinson" <dean at vinsonfarm.net>
To: "'Antique tractor email discussion group'" 
<at at lists.antique-tractor.com>
Sent: Friday, September 29, 2006 7:27 AM
Subject: [AT] Compression values and range


> Mike Sloane wrote:
>
>> Based on everything I have read about this tractor's problems, I would
>> have to say that it either has very low compression or weak spark under
>> compression. I had a Ford N that was very hard starting, and it turned
>> out that the rings were broken on two of the pistons. It would run, once
>> I got it started, but a compression check showed two cylinders with about
>> 30 pounds compression. Burned valves can also cause poor compression.
>
> Mike, I do have significantly lower compression in two cylinders than in 
> the
> other two.  #1 and 2 are at 115 and 118 psi respectively, but #3 and #4 
> are
> at 90 and 105.  90 seems mighty low compared to 118 but it's nothing like
> the 30 in your example.
>
> What do those numbers tell me?  Is 90 bad?  Or is the fact that it's
> different from the other ones bad?  I assume the lower numbers mean worn
> rings but probably not broken ones, and the tractor ought to run fine for
> what little work I'm going to ask of it.
>
> Dean Vinson
> Dayton, Ohio
> www.vinsonfarm.net
>
>
>
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