1948 8N Low Oil Pressure

[canald]

I have a question. I rebuilt my 8n engine. All tolerances are within spec. My oil pressure at startup is about 60psi, verified with an independent gauge, then at running temp at idle, it is about 5 psi. I pulled the pan and checked rod and main bearings and oil pump, good. I rechecked the torque, good. After some thought, I have not checked the cam clearances. Would that affect oil pressure? What can I do about it? There aren't any cam bearings. Thanks.

 

[Blackhole49]

What all did the rebuild include? To some it is a set of rings. To others, pistons, sleeves, bearings, new oil pump, etc. What was the pressure before the rebuild? My worn out 8n idles at +- 600 and oil pressure will go that low when hot. It goes back to 25 (as good as it gets) with a couple hundred rpm increase. It's been doing this for the 20 years I've owned it. At what rpm does yours go back to 60? https://forums.yesterdaystractors.com/threads/ford-8n-cam-bearings.765729/ https://www.google.com/search?q=does+a+ford+8n+have+cam+bearings&sca_esv=72aaa3890415b76e&sca_upv=1&sxsrf=ADLYWII4mpbMrfXiHNQnlS8711iyW-P9pQ:1726582449004&ei=sI7pZvP3PJ21wN4P8bDQyAY&ved=0ahUKEwjzj7HslMqIAxWdGtAFHXEYFGkQ4dUDCBA&oq=does+a+ford+8n+have+cam+bearings&gs_lp=Egxnd3Mtd2l6LXNlcnAiIGRvZXMgYSBmb3JkIDhuIGhhdmUgY2FtIGJlYXJpbmdzMggQIRigARjDBDIIECEYoAEYwwRIzaMBUN0QWNp1cAF4AJABAJgBcKABvQmqAQQxMS4yuAEMyAEA-AEBmAIOoAKLCsICDhAAGIAEGLADGIYDGIoFwgILEAAYgAQYsAMYogTCAgsQABiwAxiiBBiJBcICCBAAGIAEGKIEwgIIEAAYogQYiQXCAgcQIxiwAhgnwgIEECEYCsICChAhGKABGMMEGAqYAwCIBgGQBgeSBwQxMC40oAePNg&sclient=gws-wiz-serp

 

[montidale]

A couple years back I rebuilt an 8N engine for my neighbor. We replaced the oil pump gears with the rebuilt. Put it all back together and start it up and it had low oil pressure. turns out the new oil pump Gears were .010 too small. went to two other places before I got the correct gears. So if you change the gears, you might check that.

 

[montidale]

Also, you could try posting your question over at the 8N board. Lotta knowledgeable folks there. The problem I had with the small gears in the oil pump is I never had good oil pressure to start with. So it did not act quite the same as the way your engine is acting. I guess I’m just throwing things out there to look at. good luck finding the problem.

 

[Duner Wi]

What weight oil are you using?

 

[Geo-TH,In]

I have a question. I rebuilt my 8n engine. All tolerances are within spec. My oil pressure at startup is about 60psi, verified with an independent gauge, then at running temp at idle, it is about 5 psi. I pulled the pan and checked rod and main bearings and oil pump, good. I rechecked the torque, good. After some thought, I have not checked the cam clearances. Would that affect oil pressure? What can I do about it? There aren't any cam bearings. Thanks.

If you can't figure out why you have low oil pressure, I would suggest you adjust the idle to get the oil pressure you want.
My GMC truck has 60 psi and 20 psi at an idle. Been that way since it was new.

 

[Hobo,NC]

I have a question. I rebuilt my 8n engine. All tolerances are within spec. My oil pressure at startup is about 60psi, verified with an independent gauge, then at running temp at idle, it is about 5 psi. I pulled the pan and checked rod and main bearings and oil pump, good. I rechecked the torque, good. After some thought, I have not checked the cam clearances. Would that affect oil pressure? What can I do about it? There aren't any cam bearings. Thanks.

I would want to know the health of the oil pump and oil pump pickup I focus on the suction side. The suction side health will tell you most all you need to know if the pump is go-no go. If the pump instantly pulls oil off the starter only the pump is not the issue you will have to dig deeper. A healthy pump has no delay with suction the suction is rat now.

New Motor, No Oil Pressure

OK, rebuilt many a motor but never a flathead. Total rebuild including new oil pump gears installed to specs. Also installed a WIX spin on, plumbed the right way. I tried to preprime the pump by pouring oil into the uptake tube, but I imagine it wasn't too effective once the motor was rotated...

forums.yesterdaystractors.com

 

[Dean]

I have a question. I rebuilt my 8n engine. All tolerances are within spec. My oil pressure at startup is about 60psi, verified with an independent gauge, then at running temp at idle, it is about 5 psi. I pulled the pan and checked rod and main bearings and oil pump, good. I rechecked the torque, good. After some thought, I have not checked the cam clearances. Would that affect oil pressure? What can I do about it? There aren't any cam bearings. Thanks.

Excessive clearances in the oil pump. VERY common.

Installing on oil pump rebuild kit will not help hot idle oil pressure because much of the wear is in the oil pump housing which is integral to the front main bearing cap. Doing so often makes hot idle oil pressure worse because the Chinese made oil pump gears are oftentimes out of spec.

The only way to properly correct this issue is to install a new oil pump housing (and kit) all of which is within spec (no idea where one could buy such) and align bore the block as required to accept the new front main bearing cap. Almost no one does this due to the associated costs.

Most folks simply live with it.

 

[Janicholson]

I have a question. I rebuilt my 8n engine. All tolerances are within spec. My oil pressure at startup is about 60psi, verified with an independent gauge, then at running temp at idle, it is about 5 psi. I pulled the pan and checked rod and main bearings and oil pump, good. I rechecked the torque, good. After some thought, I have not checked the cam clearances. Would that affect oil pressure? What can I do about it? There aren't any cam bearings. Thanks.

20w-50 oil may solve the unsolvable pressure issue. Though not a winter oil it might bring it up to 10psi at warm Idle. The low pressure at idle is usually not a critical aspect. 5psi will keep things lubricated. at idle there is no load on the engine, so oil has an easy job. Jim

 

[canald]

What all did the rebuild include? To some it is a set of rings. To others, pistons, sleeves, bearings, new oil pump, etc. What was the pressure before the rebuild? My worn out 8n idles at +- 600 and oil pressure will go that low when hot. It goes back to 25 (as good as it gets) with a couple hundred rpm increase. It's been doing this for the 20 years I've owned it. At what rpm does yours go back to 60? https://forums.yesterdaystractors.com/threads/ford-8n-cam-bearings.765729/ https://www.google.com/search?q=does+a+ford+8n+have+cam+bearings&sca_esv=72aaa3890415b76e&sca_upv=1&sxsrf=ADLYWII4mpbMrfXiHNQnlS8711iyW-P9pQ:1726582449004&ei=sI7pZvP3PJ21wN4P8bDQyAY&ved=0ahUKEwjzj7HslMqIAxWdGtAFHXEYFGkQ4dUDCBA&oq=does+a+ford+8n+have+cam+bearings&gs_lp=Egxnd3Mtd2l6LXNlcnAiIGRvZXMgYSBmb3JkIDhuIGhhdmUgY2FtIGJlYXJpbmdzMggQIRigARjDBDIIECEYoAEYwwRIzaMBUN0QWNp1cAF4AJABAJgBcKABvQmqAQQxMS4yuAEMyAEA-AEBmAIOoAKLCsICDhAAGIAEGLADGIYDGIoFwgILEAAYgAQYsAMYogTCAgsQABiwAxiiBBiJBcICCBAAGIAEGKIEwgIIEAAYogQYiQXCAgcQIxiwAhgnwgIEECEYCsICChAhGKABGMMEGAqYAwCIBgGQBgeSBwQxMC40oAePNg&sclient=gws-wiz-serp

Complete. Rings, pistols, turn crank, main and rod bearings, machine connecting rods, oil pump including brass sleeve. Head was ok. New gasket set. Timing gears replaced, oil pressure relief spring and plunger replaced. In other words, I replace most everything.

 

[canald]

A couple years back I rebuilt an 8N engine for my neighbor. We replaced the oil pump gears with the rebuilt. Put it all back together and start it up and it had low oil pressure. turns out the new oil pump Gears were .010 too small. went to two other places before I got the correct gears. So if you change the gears, you might check that.

Yep, took off the oil pan 4 times to ensure I didn't miss something. The only thing I didn't do was check the cam clearances. The lobes looked great. She runs like a champ. This engine had been rebuilt before. I shut her down 3 years ago back there was a knock. She still had good oil pressure of 40 psi hot. Never found anything. May have been a sticky lifter. I don't want to damage the block.

 

[canald]

What weight oil are you using?

Straight 30. I tried 40, no difference.

 

[docmirror]

Another vote for oil pump gears, or intake, or pressure spring. Something in the oil delivery circuit is not right.