[Public-List] atomic 4 compression test

George Dinwiddie gdinwiddie at alberg30.org
Sat Dec 1 11:09:46 PST 2012


On 12/1/12 11:27 AM, Sandi & Mark Bisset wrote:
> We are currently rebuilding an old Atomic 4 and trying to determine a
> baseline for compression. We were testing the engine when it was
> cold, using a battery, and got results in the 100-110 range. Adding
> oil increased compression to 115-125ish. The plugs are fouling very
> quickly in regular useage (black soot, not oily) and the engine is
> running rough at times with significant vibration. It has been
> suggested that it needs a ring and/or valve job. But the compression
> seems to be in the specified range.

That's good compression. Evenness between cylinders counts for more than 
the number. People have done fine with 90. Over 125 I would start to 
worry about blowing out the head gasket. The use of two head gaskets is 
(at least partly) to keep the compression low enough.

  - George

   When I remember bygone days                         George Dinwiddie
   I think how evening follows morn;            gdinwiddie at alberg30.org
   So many I loved were not yet dead,           http://www.Alberg30.org
   So many I love were not yet born.                          also see:
                'The Middle' by Ogden Nash     http://idiacomputing.com


More information about the Public-List mailing list