Farmall H engine question

Before you adjust the carb however check to be sure there’s no restriction in the air cleaner (run it with the air inlet tube temporarily disconnected). Also that the choke plate is open all the way when the choke rod is pushed in.

Then try turning the high speed screw in (clockwise) ¼ turn at a time until the black just disappears and the engine still picks up without stumbling when you snap open the throttle. Only if the high speed screw bottoms out and it still smokes black will you need to go inside the carb to look float settings, etc.

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Regarding the low oil pressure situation, first thing I’d do is switch to multi-grade oil (10W30 or 15W40). Multi-grade will make a significant difference in oil pressure when the engine is warm – especially if the straight 30 oil currently in the engine is diluted with gas from the carb running rich (which it probably is by now….)

Other possible causes are a worn, warped or loose oil pump cover, or worn main/rod/cam bearings as others note. However as long as ANY oil pressure shows on the gage at warm idle and oil pressure rises when RPM’s are increased, the engine will enjoy a long life just the way it is.

The same procedure can be followed for idle mixture with the addition of the ldle stop screw to set the low speed RPM.
On the "H"& “M” carb, the idle mixture screw is an air adjusting screw so turning in will richen the mixture and out will lean the mixture.
Repeat the procedure again to make sure “all is well”.

Someone may have replaced the bearings but not the cam bushings, resulting in loss of oil there. If you don't use the tractor for a lot of hard work you may find you get acceptable results by running 20w50 motor oil.

Vern

A little black smoke is normal at idle if you have the screw set to work it hard. The screw should be set so the engine does not miss under load, otherwise in as far as possible.