F-20 Compression Range ?

Anonymous-0 · Oct 22, 2008

What should the acceptable compression range be for a '39 F-20 that used to have a dual fuel manifold ? Currently has the gas-only manifold. This engine was also set to run at 1250 rpm verses the 1100 that most tractors were set for.

Did a test last night. Dry are in the 55-60psi range. Wet are similar.

Thanks !

Anonymous-0 · Oct 22, 2008

I think you're probably good enough, all four cylinders being pretty even is a real good sign, I wouldn't fool with it. They are not a high compression engine. Your valves can't be too bad, hose the stems down good while it is running to make sure they aren't sticking, I would guess your intermitent miss is in the ignition.

Andy Motteberg · Oct 22, 2008

That sounds alright for a all-fuel engine.

LenNH · Oct 23, 2008

All the dual-fuel engines had a "low-compression ratio," probably around 4 to 1, because the higher compression used with gasoline would cause serious knocking with kerosene or distillate. I have never seen this number publicized for the F-20, but there may be someone out here in Tractorland who knows.
I have always wondered if the 2-bearing crankshaft would hold up to a 6 to 1 compression ratio (typical for gas). Lots of people got tired of the problems of using kerosene (two fuels needed; a nuisance to start on gas and then switch; need to keep the engine hot for it to run well; need to drain the carb of kerosene if it stalled and cooled off). Everybody I knew with F-20s back in the 40s used gasoline, but with the low compression ratio, I don't suppose the tractor put out too much more power than on kerosene. With a high-compression engine, this thing would be a tiger. It was anyway if on rubber, compared to its performance on steel.

F-20 Compression Range ?

Anonymous-0

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Anonymous-0

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Andy Motteberg

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LenNH

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