49 8N low oil pressure when engine is hot. Cam bearings??

[canald]

Canald, Maybe this doesn't need to be said but please don't forget to post back once you find your problem, the fix and the method you used to find it. Lots of good information in this thread and I have a similar problem that eventually I will need to address. Hobo, great info.

I will. Right now I'm working on the plow truck, snow season in Colorado. I'll get back to the 8N soon.

 

[TheOldHokie]

Ok. I started talking about this in another thread. I was asked, by another member, to start a new thread for this discussion. So here goes.
I completely rebuilt my engine. Running straight 30w oil, I get 60psi oil pressure. As the engine gets warmer, the pressure drops to below 5 psi at idle. I raise the rpm a bit and the oil pressure doesn't come up much. I've read all the other threads about using different weight oils. I think that I should have great oil pressure with 30W oil. I live in Colorado and use my tractor in winter. Anyway, I thought maybe I screwed up somewhere. I dropped the pan and plastigaged the crank and rod bears, with in spec. Pulled the oil pickup tube, pressurized it under water, no leaks. Checked the oil pump, which was rebuilt, all in spec. Oil relief spring and plunger new.
The only thing I didn't measure was the cam journals and block bore. I have a front distributor engine and can't find a new cam. I think this is the original cam. The journals are not black or scored and the lobes have nice peaks not rounded. The other thing I did change, I originally had a non proofmeter governor and I installed a governor that would run a proofmeter. The only reason I mention the governor is because it uses oil pressure to operate.
After all that, my question is "could the cam journals affect oil pressure when hot"?
I think the answer is yes, if like car engines. What can I do about it??
I have not found specs for the cam journals. I do have service manuals for the 8n.
I have not found a thread about the cam on any forums.

Did you measure the face width of the oil pump gears and if so what is that measurement?

If you did not measure those gears and confirm they are correct there is a very good possibilty the gears are undersize and giving you low oil pressure at operating temperature.

Dan

 

[canald]

Yep good info as i am not sold all he states he has checked to spec. BTDT and missed a my shot that's why I jumped ship with all this talk about oil I am not riding that boat. The problem is in his sites he needs to confirm the easy stuff that can be missed. TOH has taught us to not overlook what we get to rebuild a oil pump I know I will not skip over those parts again.

I did not measure the oil pump gasket that came with the rebuild kit. I did not measure the clearances on the Cam journals. Didn't find the specs in the manual. I did check that the pickup tube was not leaking by pressurizing the tube, under water, to about 25 psi, no leak. However, I don't remember the clearances that I measured, but I assure you that I measured the main and rod bearings with Plasti Gauge, the internal measurements of the oil pump clearances per the service manual. But here in the near future, I will drop the oil pan to check the oil pump gasket (face) clearance.

 

[canald]

Did you measure the face width of the oil pump gears and if so what is that measurement?

If you did not measure those gears and confirm they are correct there is a very good possibilty the gears are undersize and giving you low oil pressure at operating temperature.

Dan

Ok. To answer some of your questions.
1. Cranking the engine with ignition off. I still have to 6v system, slow crank. After about 20 seconds of cranking, straight 30w, 45 degrees, I did get oil pressure to about 10 to 15 psi. I tried this a few times, got same results.
2. Pulled the oil filter, cranked again with ignition off. Oil came I to filter housing. I also checked that there was a small hole in the shaft for the governor.
3. Question for you guys, my tractor is all original except for the governor. This one can run the proof meter. Should there be a restricted anywhere in the oil lines. From the "T" block all the way to the governor. As I had stated before, I replaced many brass fittings, in that length of oil line, because they were rounded. I may have missed one.
Again thanks for your help.
Dan

 

[canald]

Here are some pictures.
One other mod. I replaced all the head studs with like length grade 8 bolts. The studs were sloppy on the block holes. Rusted.

 

[Hobo,NC]

Ok. To answer some of your questions.
1. Cranking the engine with ignition off. I still have to 6v system, slow crank. After about 20 seconds of cranking, straight 30w, 45 degrees, I did get oil pressure to about 10 to 15 psi. I tried this a few times, got same results.
2. Pulled the oil filter, cranked again with ignition off. Oil came I to filter housing. I also checked that there was a small hole in the shaft for the governor.
3. Question for you guys, my tractor is all original except for the governor. This one can run the proof meter. Should there be a restricted anywhere in the oil lines. From the "T" block all the way to the governor. As I had stated before, I replaced many brass fittings, in that length of oil line, because they were rounded. I may have missed one.
Again thanks for your help.
Dan

First I have never preformed this check on a 6V system so I understand slow cranking. On everything I have checked this way the oil sender has been close to the pump so I would expect an immediate reaction cranking. In this case With a few turns of the crankshaft I should see some reaction in oil pressure. If in doubt I move to the suction side of the pump where I should see an immediate reaction to movement of the crankshaft.

If the suction side has a small leak a good pump can overcome that you will see a delay in oil pressure till the pump completely fills the suction side circuit. I want to see an immediate reaction period even if I put mu finger over the end of the pick up tube I want to feel it suck NOW not 2,3,4,5 seconds later.

I know this is a pain but its also a pain to go in blind spend $$$ plus time and lose the battle. I have lost those battles felt the loss it hurt to tell the customer I lost the engine needs to come out for a tear down. I know I should have been capable to catch this but to lazy to go the extra mile. 15 Psi off a 6V starter I an feeling good about the oil pump I would have to know how the suction side is working, drain the oil put your finger over the end of the pick up tube are put a 1/2" hose over it and a vacuum gauge you should see no delay in suction it should be immediate and pull a good vacuum.

Its just down and dirty no magic needed.