Oil Pressure (1 Viewer)

[Stevepipeman]

I have a freshly overhauled 71 1F motor w/ new pistons, rings, bearings, cam and lifters. Block and head were professionally machined and rolling assembly was professionally assembled after I bailed out on the initial assembly, due to what I thought was a tight turning crank. I never came close to starting the engine before taking it back to the shop. I was surprised because the crank resistance wasn't much different when I got it back than when I assembled it. The machinist told me I was way too over cautious. Consequently, I finished the assembly and it started and ran fine for its 20 minute break in run and has been running fine for the 100 miles I've put on it. My issue is, after getting warmed up and driving for a while, I'm losing oil pressure and I've only got about 45lbs max before bottoming out around 30psi at 3000 rpm and down to 20lbs at 650 rpm. I did NOT change the oil pump when rebuilding. I drove the truck for 1000 miles before the rebuild and the oil pressure seemed to hang around the middle of the standard factory gauge. That gauge failed prior to removing the engine, so I have no baseline to compare, but I'm concerned about only 40lbs at cold start. I installed an analog pressure gauge by tapping a hole in boss(see picture) of the discharge outlet at the top of the oil filter housing. I did bench test the pump and volume of flow seemed substantial and I primed the hell out of the motor before initially starting.
During the rebuild, I removed, disassembled and cleaned the pressure regulator and reinstalled it. I used no specific information for adjusting it. I know from my own readings and numerous plasti-gauge measurements that there no slop in bearing tolerance. I have removed the oil filter and opened it, looking for metal or particles in the oil. It runs cool and as quiet as a 1f will run.

 

[SteveH]

Fortunately, you have enough pressure that you're not damaging things during this fact-finding mission.

What weight of oil are you running? I would measure the oil at the factory sending port location. Can you shim the oil pressure regulator more aggressively to see if that forces a higher pressure? I stuck a few washers under the spring of the regulator on my Massey Ferguson tractor and how have lots of pressure.

 

[Stevepipeman]

Fortunately, you have enough pressure that you're not damaging things during this fact-finding mission.

What weight of oil are you running? I would measure the oil at the factory sending port location. Can you shim the oil pressure regulator more aggressively to see if that forces a higher pressure? I stuck a few washers under the spring of the regulator on my Massey Ferguson tractor and how have lots of pressure.

Still running SAE30 (zink rich) Break in oil and need to run it for 500 miles. I'll see what I can do with the pressure regulator and get a pressure reading from sending unit location. Thanks for your time and input. Take care.

 

[73FJ40]

@Stevepipeman

I believe a more representative location for reading oil pressure would be at the port that the oil pressure sending unit is located.

I believe the oil filter housing is downstream of the pressure regulator on the F engine. The discharge line flows back to the oil pan. I suspect that the pressure you're reading is effectively the pressure drop through the return line to the oil pan.

 

[Stevepipeman]

@Stevepipeman

I believe a more representative location for reading oil pressure would be at the port that the oil pressure sending unit is located.

I believe the oil filter housing is downstream of the pressure regulator on the F engine. The discharge line flows back to the oil pan. I suspect that the pressure you're reading is effectively the pressure drop through the return line to the oil pan.

Thanks for that info. As you know, the the block is tapped with an 8x1.25 mm female thread and I've had a hell of time finding anything but NPT (national pipe thread) gauge connectors. I didn't want to drill and retap the block so I tapped the filter housing NPT.

 

[SteveH]

You might look for a metric oil pressure gauge adapter kit. They were widely sold at auto parts stores many years ago - now probably on Amazon. They don't always have what you need, but after years of cobbling stuff together and buying these kits, you'll have a drawer with 20-odd brass adapters and one might/will fit For temporary testing (while I'm standing there watching) some US-threaded adapters will fit well enough to start and run the engine for 5 minutes. Just don't overtighten them or walk away from a janky connection.

 

[73FJ40]

Thanks for that info. As you know, the the block is tapped with an 8x1.25 mm female thread and I've had a hell of time finding anything but NPT (national pipe thread) gauge connectors. I didn't want to drill and retap the block so I tapped the filter housing NPT.

What I know (based upon actual experience, see picture below) is that the stock oil pressure sending unit is 1/8" BSPT male, (British Standard Pipe Tapered) and the block is tapped for 1/8" BSPT female. (unless a PO messed with it.)


You can get an adapter (1/8" male BSPT to 1/8" female NPT) and a 0 - 100 psig 1/8" NPT back mount pressure gauge to take the place of your sending unit. $10 for the adapter and $10 for the gauge on Amazon, or anywhere else you may choose.

 

[Stevepipeman]

You're right. That's what I'll do. Thanks for the help.

 

[flee]

I recently completed my F rebuild and figured an oil pressure gauge would be a nice addition in the engine compartment, too.
I got everything pictured from McMaster-Carr Supply, one-stop shopping! It is all 1/8" BSPT and fits together nice and tight.
My pressure does decline as the oil warms up but not enough to worry me.

 

[Stevepipeman]

I recently completed my F rebuild and figured an oil pressure gauge would be a nice addition in the engine compartment, too.
I got everything pictured from McMaster-Carr Supply, one-stop shopping! It is all 1/8" BSPT and fits together nice and tight.
My pressure does decline as the oil warms up but not enough to worry me.
View attachment 2548385View attachment 2548380

Nice looking work. You've added the gauge while keeping the OEM pressure gauge functional. I have an account with McMaster. Is that a straight 1/8" BST Nipple with

I recently completed my F rebuild and figured an oil pressure gauge would be a nice addition in the engine compartment, too.
I got everything pictured from McMaster-Carr Supply, one-stop shopping! It is all 1/8" BSPT and fits together nice and tight.
My pressure does decline as the oil warms up but not enough to worry me.
View attachment 2548385View attachment 2548380

 

[Stevepipeman]

Nice looking work. I've got an account with McMaster and will get it coming. Thanks for fine details.

 

[Mark Jennings]

I have a freshly overhauled 71 1F motor w/ new pistons, rings, bearings, cam and lifters. Block and head were professionally machined and rolling assembly was professionally assembled after I bailed out on the initial assembly, due to what I thought was a tight turning crank. I never came close to starting the engine before taking it back to the shop. I was surprised because the crank resistance wasn't much different when I got it back than when I assembled it. The machinist told me I was way too over cautious. Consequently, I finished the assembly and it started and ran fine for its 20 minute break in run and has been running fine for the 100 miles I've put on it. My issue is, after getting warmed up and driving for a while, I'm losing oil pressure and I've only got about 45lbs max before bottoming out around 30psi at 3000 rpm and down to 20lbs at 650 rpm. I did NOT change the oil pump when rebuilding. I drove the truck for 1000 miles before the rebuild and the oil pressure seemed to hang around the middle of the standard factory gauge. That gauge failed prior to removing the engine, so I have no baseline to compare, but I'm concerned about only 40lbs at cold start. I installed an analog pressure gauge by tapping a hole in boss(see picture) of the discharge outlet at the top of the oil filter housing. I did bench test the pump and volume of flow seemed substantial and I primed the hell out of the motor before initially starting.
During the rebuild, I removed, disassembled and cleaned the pressure regulator and reinstalled it. I used no specific information for adjusting it. I know from my own readings and numerous plasti-gauge measurements that there no slop in bearing tolerance. I have removed the oil filter and opened it, looking for metal or particles in the oil. It runs cool and as quiet as a 1f will run.

View attachment 2546658

View attachment 2546660

Your oil pressure 45 cold and 30 hot, and drifting to 20 at idle hot is not abnormal. The external relief on these old engines limited pressure to 55 lbs. You can increase pressure a bit by screwing ‘in’ the external relief. Don’t overdo it...and certainly don’t back it off.

I run 15w40 in my F (rebuilt 5k miles ago) and see maybe 50 on cold mornings and after warm up, it runs 35 to 40 when cruising at a lazy 25 to 2700 rpm. At idle when hot it drifts down to 20.

I run a Dakota Digital dash and the sending unit came with a metric pipe to NPT adapter...and the sending unit/pressure indication lines up with a mechanical gage, e.g. pressures are the same within a few lbs.

Bottom line....I think your oil pressures are fine.

 

[flee]

Nice looking work. You've added the gauge while keeping the OEM pressure gauge functional. I have an account with McMaster. Is that a straight 1/8" BST Nipple with

Affirmative. I went with a hex nipple for ease of adjustment and removal.

 

[Stevepipeman]

Your oil pressure 45 cold and 30 hot, and drifting to 20 at idle hot is not abnormal. The external relief on these old engines limited pressure to 55 lbs. You can increase pressure a bit by screwing ‘in’ the external relief. Don’t overdo it...and certainly don’t back it off.

I run 15w40 in my F (rebuilt 5k miles ago) and see maybe 50 on cold mornings and after warm up, it runs 35 to 40 when cruising at a lazy 25 to 2700 rpm. At idle when hot it drifts down to 20.

I run a Dakota Digital dash and the sending unit came with a metric pipe to NPT adapter...and the sending unit/pressure indication lines up with a mechanical gage, e.g. pressures are the same within a few lbs.

Bottom line....I think your oil pressures are fine.

I really appreciate your friendly and informative info. I had 2 FJ40's back in the 70's when I was in my 20's. I plowed snow for 24hrs straight, explored power line trails and mud bogged every chance I got, beating the hell out of those trucks, while my buddys' CJ5's fell apart. Over 40 years later, you'd think I'm some dick fussin over his 911, worried I'm gonna break something. I've spent 3 years restoring this rig, to the best of my ability. Thanks to guys like you, I might have a pretty nice old cruiser one of these days.

 

[SteveH]

The racer's rule is 10 psi per 1000 rpm, so you are within that. Old International Scouts typically had very low oil pressure all the time. My 22R-equipped '82 Toyota pickup had about 9-10 psi at hot idle, which scared me a bit, but the spec was 'greater than 4.3 psi' so I was within the limit. My chevy plow truck shows 20 psi at hot idle after a plow-fest and that engine is fairly tight. So, your engine is looking just fine from my perspective.

 

[Stevepipeman]

The racer's rule is 10 psi per 1000 rpm, so you are within that. Old International Scouts typically had very low oil pressure all the time. My 22R-equipped '82 Toyota pickup had about 9-10 psi at hot idle, which scared me a bit, but the spec was 'greater than 4.3 psi' so I was within the limit. My chevy plow truck shows 20 psi at hot idle after a plow-fest and that engine is fairly tight. So, your engine is looking just fine from my perspective.

Thanks for taking time to reassure me on that.