51 va oil pressure

Would anyone know the diameter of the ball (part # vt4146) in the oil pressure valve located in the support casting of the oil filter. "Missing" could be part of the low oil pressure problem. Thanks in advance Guys John
PS parts catalogue R.I. E61 pg. 7

VA series engines are designed as low oil pressure engines, I've been told. They should hold about 15lbs at full throttle and 1/2 that at idle when warmed up. Original gauges only show 30 at max. jal-SD

jal On start up shows as high as 11 lbs then drifts down to about 7 lbs on warm up.
But that ball is still missing, worries me. Thanks for your reply. JDL

Few of the VA series that I've owned or worked on around here have a differential relief valve in the holder base, I don't think it was very common in the VA or other 300/00B series tractors all of which use this type filter base (pic 1 is typical). I really don't understand the rationale for having a differential pressure relief valve in a by-pass type oil filter circuit. If the filter element becomes plugged enough to crack the differential valve open the oil pressure will only drop a couple psi. The ball missing in the valve is about the equivalent of having a missing stem tube that directs the oil to the top of the filter media. Depending on a good pump and not excessive bearing wear that is typically about 2 psi. Of course you want to plug that bypass with a new ball that works or some other way.

I think you could buy an assortment of balls at a hardware and find one that fits. If I needed the tractor, I would just mount the base with a blind piece of gasket material to eliminate the oil filter circuit. There are many VA series tractors surviving today that did not come from the factory with an oil filter, just a blank cover where the base mounts on the block.

The best way to get a basic oil pressure check on this type engine is pull the valve cover, with the engine warmed up you should have enough oil flow to lube the running gear and running down the push rod holes to lubricate the cam. The top deck is the end point of the lube system and the immediate and rear cam bearings are lubed by top deck oil run-off as well as the lifters/lobes.

If your oil gauge is unknown you can tap a good 0 - 30 psi gauge into the oil galley plug that isn't being used for the dash gauge for comparison. IIRC The tread is either 1/4" or 1/8' npt.

Joe

This is an old pic that shows a cutout view of the filter assembly with a differential pressure valve. It might not post clear enough to be legible?

Joe

5/16"

Thank You John Saeli for the size, your time is much appreciated by this amateur JDL

Great reply Joseph, It finally clicked what Case was trying to do here. I have been going through 4 different manuals trying to solve what I thought was rather low pressure. Many thanks for your explanations and your TIME. I will certainly get another ball in there before startup. JDL