MGB Oil pressure

[Aussie Chris]

Hi to all
My 1974 MGB from cold start has oil pressure 80psi and usually stays around that mark . It has increased up to 90 psi after engine got warm should I be worried ? Engine was totally rebuilt with new oil pump about 12 months ago
Regards
Aussie Chris

 

[YakkoWarner]

To me that sounds almost too high; especially if it goes UP after warmup. Rebuilt engine and new pump should put out good pressure, but going up after warmup sounds odd. Did they go back to an actual plumbed pipe pressure gauge in 1974 or does it still have the electrical sending unit (my 1970 has the electrical unit, I know in 1977 they used a plumbed pipe). I'd consider hooking up a mechanics' oil pressure test kit and verify that the dash readings are what the engine is really delivering. If it is, verify there is no blockage in the external lines or in the oil cooler?

 

[DrEntropy]

Hi Chris. On cold start 80psi is not unusual in a fresh engine, but you should see a drop after it gets to normal operating temp. Someplace around 40-ish at idle and 60 on revs. over 2K. As Yakko suggests, a blockage in cooler lines is possible. I'd think more along the lines of a too-strong spring (or too many shims) in the pressure relief valve. Just be aware that spring and cap are a real bugger to push back in far enough to start the threads when the engine is in the car.

 

[DrEntropy]

I'd consider hooking up a mechanics' oil pressure test kit and verify that the dash readings are what the engine is really delivering. If it is, verify there is no blockage in the external lines or in the oil cooler?

Forgot it may be electrical OP gauge. A "hard" mechanical gauge would be a good first step.

 

[mezy]

Have you by any chance filled with fully synthetic oil, as this thickens when it gets warm.

 

[Aussie Chris]

Have you by any chance filled with fully synthetic oil, as this thickens when it gets warm.

Just normal Castrol 20 50 now that I am paying attention to it the pressure on cold start goes to 80 then basically
stays their it will vary 10 either way depending on what you are doing

 

[Aussie Chris]

Forgot it may be electrical OP gauge. A "hard" mechanical gauge would be a good first step.

Hi Doc ,
I read that some oil filters because don’t have much space between the the feed pipe and the top of the filter can create higher pressure does it sound feasible if so I am using a coopers wz89 filter at present do you think it’s worth replacing ?
Aussie Chris

 

[PAUL161]

Chris, Try doing the easiest first, such as changing the filter with a different brand if that doesn't lower the pressure check with a hard line mechanical gauge to see if your electrical gauge is out of calibration. The last option, because it's a PITA, would be to change the bypass spring pressure. If none of those work you have a blockage somewhere.

 

[Aussie Chris]

Hi Chris. On cold start 80psi is not unusual in a fresh engine, but you should see a drop after it gets to normal operating temp. Someplace around 40-ish at idle and 60 on revs. over 2K. As Yakko suggests, a blockage in cooler lines is possible. I'd think more along the lines of a too-strong spring (or too many shims) in the pressure relief valve. Just be aware that spring and cap are a real bugger to push back in far enough to start the threads when the engine is in the car.

Hi Doc,
Hope you had a great festive season, finally with nothing to do so I reconnected the old smith gauge to check oil pressure
65 to 70 on start up and 70 to 75 after warm up and on the road running between 50 to 60 mph . The new Smiths gauge from England was showing 95 psi under same conditions so all good just not impressed with new gauge and talking to supplier.
Regards
Chris

 

[DrEntropy]

The new Smiths gauge from England was showing 95 psi under same conditions so all good just not impressed with new gauge and talking to supplier.

Glad to learn it's not your engine!