farmall c low oil pressure

With all respect, it is engine design that determines if low oil pressure is acceptable.

The vintage Chevy’s you refer to (40’s and early 50’s) were designed to be low pressure (lower than 30 with 15 being a “normal” reading) oil systems. The connecting rod bearings were oiled by the oil pump delivering oil to troughs under the connecting rods. The connecting rods had “dippers” on them that dipped into the oil and oil lubed the bearings through a hole in the rod cap to the crank surface. Most other parts of the engine were lubricated from the "splash" from the rod dippers and catch troughs and oiling holes. Some of the older Farmalls (F-20 for example) were the same way as well as many of the V-4 Wisconsin engines. Those Chevy’s also had a notorious habit of throwing the # 5 rod through the right side of the block if they were revved to high.

However GMC trucks of the same era were a high pressure oil (normal reading 30 psi or more) system with a drilled crankshaft. The oil was supplied to the rod bearings via passages inside the crankshaft. To get the oil into the bearings it was necessary to have higher oil pressure. The F-12/14 A, B, C, H, M and newer all have the high pressure oiling systems. Normal oil pressure for these engines is over 30 pounds (M’s in good shape will have more than 60 psi).

The stock B and C (may be others also) oil pressure gauge is mounted on the oil filter base and does not take the reading off the cam bearings. If the gauge is working correctly and shows low oil pressure, then there is an issue in the engine that needs to be corrected. Since the A, B, C and a few other models are notorious for warping oil pump plates and having “chunks” of gasket missing, this is likely the cause and should be corrected since this engine is designed to have higher oil pressure. In this case not only is the oil pressure low, but also the oil volume to the crankshaft is also. Ignoring the problem may lead to premature wear inside the engine including rings and pistons.

with all due respect to you...as it appears you are a farmall mechanic and I stated I didnt know much about them..... if the man has been running the tractor for 6 years and it hasn't siezed yet....Logic would indicate that enough oil is being forced somewhere important to keep things lubricated.

I also think many people are so hung up about some things.....they demand perfection and books specs on everything they mike or gauge.....if not, it is panic city and they grab their wallets and start buying rebuild kits, machine shop time, and hours in the garage..... .all so when they fire the engine up, the oil gauge reads maxiumum readings, they can brag on the engine...and sleep at night. Most of these tractors are like us.....getting older and beyond their prime. And as for where oil pressure is held....unless there is a restriction (bearings) in the oil gallery/system....there can be no pressure built as it (pressure) is a measurement of restriction against the pump. Most oil systems send the oil to the cam bearings FIRST and the upper engine....rockers etc. GENERALLY speaking, if the oil presure is low, it is due to worn cam bearings....and if this is the case, the rods and mains are generally worn as well. BTW, I had a 53 Chevy with 235 six...I never did throw a rod....although #5 knocked pretty bad! That was a fun old car..... ..that rod started knocking at 93 mph and I am quite sure, I could gone to 100 but backed off when the clatter got louder and louder. That rod never did let go.

See this thread for more ideas.

Good luck,
Bill

• Oil pressure thread from last week

• Hobby farm