[AT] [Farmall] Super M Fan Belt -- and other fun stuff

[drupert at seanet.com]

...
On my '50 M the four cylinders had tested at 115, 118, 90, and 105 psi,
which as I recall folks here on the list had said was okay for an old
light-use tractor.  This SM is in a lot better shape so I was expecting
higher numbers, but not what the tester showed:  180 psi, 175, 178, and
175.  High-altitude pistons?

What's a normal range for an SM?

Dean Vinson
Dayton, Ohio
www.vinsonfarm.net
...

Dean,

One further comment re: your' question on the normal compression range for
a SM.

I just looked in the data book I have and it lists the compression ratio
(CR) for a regular gasoline M as 5.65 to 1 so, on a good tight engine, I
think a compression reading in the neighborhood of a 100 psi could be
expected.

The same data book lists the gasoline SM as having a CR of 5.9 to 1.  This
increase of 0.25 in CR between the regular M and SM could be expected to
increase the SM's compression reading but I would think it would be
limited to 5 psi at most.

With your' SM having compression readings in the 175 psi range I tend to
think it has a CR of at least 9 to 1 which is what Cecil has suggested in
his post.  Incidental, this same data book lists the 400 with a CR of 6.3
and the 450 with 6.6.  When I started this post I was thinking that maybe
your' SM has the 450 Piston/Sleeve kit in it but now I am thinking that it
must have an even more aggressive Domed Piston ...it would be interesting
to know what the rebuilder put in it.  As Charlie has said, you may have a
good puller there -

Dudley
Snohomish, WA