'48 Cub oil pump quesstion

[Brett Lindberg]

I have been having low oil pressure when the engine is at operating temperature. Main and rod bearings have been replaced as well as regulator spring and valve. (The one near the front of the engine) I came across this page in the manual that shows something in the upper hole behind the oil pump.

http://www.farmallcub.info/manuals/gss- ... 001-56.jpg

I currently have the tractor split to check for wear in the oil pump body and when I checked that hole there is nothing in it. I have searched for an answer everywhere I can think of to no avail. I'm hoping someone here has come across this. Thanks for your help.

Brett

[Glen]

Hi,
Welcome to the website.
You didn't say if you meant the upper or lower picture on the manual page.
The pics are not real clear on the page.
Below is a pic from TM Tractor Parts of the rear of a Cub engine block, it says on their website it is a 1948. Maybe you can see what you need in the pic, if you can make the pic big.
There are 2 small dowel pins to align the oil pump cover.
Be sure to use a thin gasket at the oil pump cover, they have said on here that some gasket kits for Cub engines come with gaskets for the cover that are too thick, the thick gasket can make the oil pressure lower than it should be.

[tst]

did you plastic gauge the bearings for clearance when bearings were changed, if it was in spec check the oil pump housing and gears for wear and make sure the oil pump gasket is correct, many of the aftermarket ones are to thick and will cause more loss of oil pressure

[Brett Lindberg]

Thanks for the reply. The lower picture in the manual seems to show someone removing something from the top hole, but it might just be showing cleaning of the main oil gallery. I didn't plastigauge the bearings unfortunately.

[tst]

main bearings are the most important for oil pressure, so if not measured for clearance you do not know what you have

[Glen]

Hi,
I think the picture is showing a cleaning brush there partly in the oil hole.
It isn't something that is in the hole when the pump is assembled.

They have recommended on here to always use Plastigauge on every crankshaft bearing when putting the engine together, then you know that the clearances are right.
I guess you have the Cub service manual GSS-1411, the pic you posted is from it.
I suggest you take it apart if the oil pan is on, and measure the clearances.

GSS-1411 tells how to use plastigauge. The manual is at the top of the page at Cub Info, then go to Rudi's Manuals.
Section 1 is for the engine.
The Plastigauge info is on pages 1-35, and 1-50, and 1-51.
There is a table of contents beginning on page 1 of most sections, that makes it easier to use online.

Plastigauge is sold at auto parts stores, the NAPA here has it. There are different colors of it for different thicknesses, you probably need the green for the Cub.

[Brett Lindberg]

Glen and tst, thank you both for your help. My plan at this point is to get the engine on a stand and tear into it. The backlash of the oil pump gears doesn't seem excessive but I'll put an indicator on them to be sure. Also my pump housing is flat. When I checked it on my granite I couldn't get a .002" feeler gauge under it anywhere. Finally the gasket measures .007" thick which looks to be slightly thicker than what I've seen others post but not excessive either. Have a great week guys. I appreciate your time.

Brett

[ricky racer]

did you plastic gauge the bearings for clearance when bearings were changed, if it was in spec check the oil pump housing and gears for wear and make sure the oil pump gasket is correct, many of the aftermarket ones are to thick and will cause more loss of oil pressure