compression on M Farmall

Fixer · Jul 15, 2009

Have 47 Farmall M. Went through it two years ago as in cleaning it up ;and fixing whatever I could see wrong painting included. Question is. It only shows 90 psi compression. 38 hp on dyno. No smoke runs very well. Wonder if somebody put a dual fuel head o n it. Previous owner swears he put fire crater pistons in it . Four inch bore. Wonder how much difference there is between dual fuel head and gas head. Haven't gotten around to taking the hood off yet and checking. Any thoughts? Thanks Bernie Steffen

Janicholson · Jul 15, 2009

Two possible items.
Make sure the compression gauge is accurate. Check it against a good pressure gauge on an air line.
make sure the throttle is open, and all the sparkplugs are out when checking the compression.
The date of the engine (if original) would make it about 50/50 on distillate. does it have the hole in the hood for the small gas tank/
Look up part numbers in the caseih.com websight to determine your part number. (under the valve cover) JimN

Anonymous-0 · Jul 15, 2009

the compression sounds a little low it should be about 100-115. I have put many 4 inch bore with a SUPER M head on farmalls and it pushes about 50 horse on a dyno. the better m gives a litttle bit more but yours should be around 45 even close to 50 with firecraters in there.

Fixer · Jul 15, 2009

Thanks for the replys guys. The reason I started this query was because I just started redoing a 400 that has been sitting for five years. Got it running. Checked compression 125 lbs. Don't know what pistons are in it. I will check the gage with my air compressor. Throttle was open. all plugs were out. This is one of the gages that screws into the sparkplug hole so no chance of error there. Am going to pull the valve cover and see what head this is.
The tractor is definatly not a all fuel. thanks again for the replys. Bernie Steffen

Red Mist · Jul 15, 2009

Bernie: Don't know if this will help you or not. My SM has 4-1/8" bores, stepped pistons. Probably 48-50 hp on a dyno - don't know, never had it on one. However, it is plenty strong for an "M" family tractor.

My compression gauge reads 120-123 across all four holes. Hope this helps you.

mike

Athol Carr · Jul 15, 2009

My recoolections of the IH sevice manuals for distillate/kerosene engines that the expected pressure was of the order of 95psi

Fixer · Jul 15, 2009

Thanks again for the replys guys. Will check head number when I get time. Bernie Steffen

Anonymous-0 · Jul 15, 2009

Bernie, if you really do have the Fire Crater or M&W or any pistons like them you should have 125 PSI and nearly 50 hp. Put the LP head, the 450 cam, carburetor, and manifold on there for almost 60 hp. You do need to tweak the governor to around 1600 rpm or better.

compression on M Farmall

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