Removing/Replacing Cub Oil Pan

Fri Dec 31, 2004 9:09 am

I have had a problem with low oil pressure on my '50 Cub for a couple of years.

Since I can't afford a full rebuild right now, I am trying the cheap fixes first. I have replaced the oil pressure gauge with a new one. It still registers low - almost in the red once it heats up even with 20W-50 oil.

Now I want to remove and clean the oil pick up screen in the oil pan.

My question: What kind of special tools will I need to remove/replace the oil pan bolts that are back in the torque tube?

Also, is there anything else that I can check while I have the oil pan off that might affect the oil pressure?

I'm afraid that it is worn crank/rod bearings, but I am trying this first since I can do it myself.

Thanks in advance for any suggestions.

Fri Dec 31, 2004 10:02 am

Don't know if you know this or not.
If you do then please forgive me for saying this.
20w50 oil is 20w oil with 50w luberacating abilitys when hot.(know my spelling sucks)
In short it is souped up 20w.

Fri Dec 31, 2004 10:09 am

Rick, you don't need anything fancy. A universal joint for your ratchet extension will likely be all you need. I have removed them using a 1/4" drive socket set with no swivels or flex joints at all.

Fri Dec 31, 2004 10:13 am

Rick while you have the pan off get som Plastigauge and check the rod and main bearings. I think you will find they have quite a bit of wear. that's the usual cause for low oil [ressure on older engines.

Fri Dec 31, 2004 11:05 am

Before you put the pan back on, take a hack saw and cut a slot in the head of the bolts you'll use for the rear. Then you can use a screw driver to get them started. Much easier :!: 8)

Fri Dec 31, 2004 12:27 pm

Rick. Also, don't forget to check the tightness of the oil pick-up tube that sucks throught the screen. If its loose or sucking air, it will cause low pressure. My best success with the back three bolts was to use a universal extension 1/4 inch drive socket. Wasn't easy, but small enough to work. Be patient.............

Fri Dec 31, 2004 1:21 pm

There are two rules of machinery and little or no oil.
1. You can pay now.
2. You can pay (much) more later
You don't want to let the lack of oil cause you to score the crank shaft or seieze up. With plasti gauge you take a bearing cap off. put the plasti gauge in and refasten the cap. Remove same and measure the thickness of the plasti gauge. New bearings if called for are no where as expensive as a complete rebuild. That way you don't lose the crank shaft nor do you throw a rod through the block.
Hey it could be the other things with the screen or oil tube but the plasti gauge will tell you it is or is not the bearings.


Fri Dec 31, 2004 5:54 pm

Rick, I'm in the process right now with the very same problem. I took my pan off (used a warbley) and then took the bearings out. They were all scratched a bit as well as the crank had very small grooves in it. There was no sense in putting new mains and rods in it the way the crank was so I took the crank out and sent it in to be turned down. I haven't got it back yet. They turn it and put the right size bearings on it. I haven't got it back yet. Its a cheap fix. $100 for the machining and 100 for the new bearings.

low oil pressure

Fri Dec 31, 2004 7:05 pm

One more thing to check before removing the oil pan is the oil pressure regulator valve. It's located on the front right side of the engine near the timing gear under a large hex plug which can be unscrewed. The spring free length should be 2-31/32". Test lenght 2-15/32@91/2 pounds pressure from a spring compressor. A picture of the regulator is in the service manual page # 1-55. Also I'm not sure if the oil filter has a bypass valve or not. Some filters or filter housings have a bypass valve to keep oil pressure going to the engine if the filter is plugged or cannot handle the flow of oil required. Some one on this site might know about the bypass valve.
If nothing else install a new filter #1, next remove the oil pressure regulator spring if it's not the correct free length strech the spring some and try again. removing the oil pan would be next. Mike

Fri Dec 31, 2004 7:13 pm

Mike Mix is right. I see he adheres to the KISS Theory.

Keep it simple stupid. That is how I felt when i had not included that.

low oil pressure

Sat Jan 01, 2005 10:14 am

The nice thing about is when you have a problem with your cub, you can get a wide variety of ideas on how to go about fixing the problem. When I started on my cub this site was and is great for the variety of information.
I've spent 31 years working on engines in a General Motors test lab and it's amazing how much I learn from the folks on this site about engines.

Sat Jan 01, 2005 6:36 pm


Thanks for all of the input on how to fix/test my oil pressure.

I tried replacing the oil pressure gauge on the Cub with ones from another Farmall and an A-C. The new one for the Cub says I hardly have any pressure; the other Farmall gauge says that the pressure is OK at about 20 psi; the gauge from the A-C says that the oil pressure is great.

So, who knows?

I think that I will take the advice from those who suggest that I Plastigauge the bearings after I have checked the oil pick-up and pressure spring.

Many thanks again to those who gave me such good advice.

Sun Jan 02, 2005 12:08 am

Maritimer wrote: I took my pan off (used a warbley)

Maritimer. Can you explain to me what a "warbley" is? Don't know if I have one of those unless it's called by a different name up north! :?

If it makes the back side pan bolts easier to work on, I'd like to get one.

Sun Jan 02, 2005 12:42 am

Its just an extention where the little square fitting that fits into the socket isa little egg shaped making it loose fitting or "warbly". It is a lot better than a universal. You have more control over it.

Sun Jan 02, 2005 6:27 am

I have heard them called "Wooblys" too.
Hey if you have an air compressor you can rig up some plumbing and make a gauge tester. With an air gauge you trust because it says the tires are right and they look right you should get the same reading on the OIL pressure gauge. Most of the regulator gauges on air compressors are close enough to use as a check on your Tire pressure gauge. If all 3 agree I would take it as gospel. If the Oil pressure differs radically from the other 2. Well you get it from there.