Help -- Engine Bearing Clearance for Cub...

Posted by Kevin Hunter on February 24, 2002 at 15:25:40 from (207.50.161.204):

I have a 1956 Farmall Cub. I have a low oil pressure situation. I have replaced the gauge. It was not the problem. The tractor has about 20 lbs of oil pressure when the engine is started. As the engine warms, the pressure will get down to ZERO during hot weather. I have switched from 30 weight oil to 50 weight oil. The heavier oil helped, but did not correct the problem.

I removed the bottom pan and used a micrometer to check the diameter of a rod bearing journal.
I found the diameter to be 1.4965". The engine currently has STANDARD bearing inserts.

I used Plastigage to check the clearance of the bearings. I found the clearance on the rod bearings to be 0.006". I found the clearance on the main bearings to be 0.007".

My stumbling block is that I do not know what the original specifications are for the bearing clearance. I'm aware that 0.002" oversize inserts can be purchased for the rods and maybe for the mains. I'm not sure how much clearance I would have if I put in NEW STANDARD bearings or 0.002" oversize bearings. I'm looking for a reply from someone who is experienced in rebuilding cub engines to give advice as to whether or not oversize bearings will help or if it needs the shaft turned and the "whole ball of wax".

BTW - I have looked at the oil pressure bypass valve spring. It is not broken, but it may be weak. I did not know of it's existence until I already had the engine apart. A new spring may have solved the problem. -- Any thoughts? Thank you.

Kevin Hunter
Willard, MO

Follow Ups:

• Re: Help -- Engine Bearing Clearance for Cub... Wayne 18:18:44 02/25/02 (0)
• Re: Help -- Engine Bearing Clearance for Cub... Steven@nd 18:03:58 02/24/02 (0)

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