Oil Pressure Questions......

Goose · Aug 19, 2011

I'm getting concerned about the oil pressure on my 1952 H Farmall. On a cold startup, it will hit 45 pounds. After warmup, it will barely move the needle at idle, and will hit 10 pounds at full throttle.

It doesn't smoke or burn oil otherwise. Good compression. It's possible the engine has never been opened up. The tractor has been in our family since 1958, and no one of us has ever gone into it.

I've replaced the guage and the oil pump, so those two suspects are eliminated.

Coupla questions. Are the cam bearings involved in developing oil pressure? Or are the rod and main bearings mostly responsible? And is it possible to replace the mains with the engine in the tractor? Or is anything else involved?

Thanks in advance.

Allan in NE · Aug 19, 2011

Yep, you got 'er,

All of 'em need attention.

Allan

Janicholson · Aug 19, 2011

The cam bearings need to be replaced with the front off of the tractor to allow the shaft to come out.
You could replace the mains by "rolling the top mains in, no real issue doing it, but the accurate measurement of the journal is tough. Plastigauge can give you a ball park, but is not too accurate with a slightly egg shaped journal. Old timers use a 3/4"X1/2" strip of brass shim stock to check the actual clearance. If it turns with .0015" and locks up with .003", it is a go. (one at a time, and torquing is necassary, do not spin it, just see if it is free to move.) Jim

agpilot · Aug 19, 2011

Goose: I'll take a chance in adding that when I use Plastigauge on the mains, I will use a very small jack and a large wooden dowl or a 1X2 to push the crank up just enough to make sure it is against the top bearing. ( guess the weight of the crank) This helps put all the clearance into the reading you will get on measuring the bottom bearing. I also tend to "try" and look for the most wear area on the crank to measure. Might as well look for worst case clearance... I was told by several machine shop guys that worn mains have the most surface so renewing them might be enough.. I also seem to recall that if you have standard bearings, there are replacement bearings that are just .002 larger to save grinding a crank.. but all this info was learned decades ago so maybe there are no .002 larger mains sold any more..?

Janicholson · Aug 19, 2011

The mains can be found in .002 undersize. The jacking of the crank is important. Undersize is a thicker insert, smaller journal "hole" Jim

Goose · Aug 19, 2011

Thanks for all the info.

After all the car, pickup, and racing engines I've built and rebuilt, seems odd I've never seriously gone into a tractor engine, in or out of frame, but that's the fact.

I'm thinking along the lines of buying another H or maybe an M to put my loader on, and taking my time with this old gal and doing it right. Paint and all.

I depend on this tractor every day, and I'd hate to do a quick, patch up fix and find I'd wasted time and money.

El Toro · Aug 20, 2011

I would pull the engine and have the crankshaft measured for wear. They wont grind it undersize unless it needs it. Buy your new bearings from them. Have the machine shop to install your cam bearings. They may need to be reamed. I would install new sleeves and pistons. Take a good look at the clutch disc if the lining is worn close to the rivets it may be a good time to have the pressure plate and clutch disc rebuilt.
Hal

buickanddeere · Aug 20, 2011

Try a heavy straight weight oil.

Oil Pressure Questions......

Goose

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Allan in NE

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Janicholson

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agpilot

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Janicholson

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Goose

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El Toro

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buickanddeere

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