Lotus Elan

Too much oil pressure?

PostPost by: Davidb » Sun Mar 15, 2020 10:41 pm

I just reinstalled my engine following a rebuild after the last rally . See viewtopic.php?f=19&t=39447&start=15#p322209 if you are interested.

I have fitted one new conrod, all new bearings, two new 420 cams with new followers and a new oil pump. The old pump was fine-I usually had 55 psi of oil pressure but I could never stop a leak between the pump and the spin on filter so I got a new pump from Burton. I did what I usually do-used the gasket as a guide to matching the inlet and outlet ports of the pump to the block ports to maximize flow using a Dremel grinder.

I just spun the engine over on the starter, with the plugs out and I am getting almost 80 psi of oil pressure! I immediately checked the box the new pump came in and it states "Standard pump". Is there any way of checking if it is a high pressure pump from external appearance?

Should I be concerned?
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PostPost by: rgh0 » Mon Mar 16, 2020 2:21 am

Sounds like the pressure relief valve inside the new pump is jammed closed or your oil gauge is faulty if getting a reading of 80 psi. To read that you don't have the standard oil gauge as they were 0- 60 psi . A standard pump should put up no more than 40 psi. A high pressure pump should put up no more than 60 psi and no real way to tell without pulling the relief valve apart and comparing to a standard pump if its a high pressure one.

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PostPost by: 2cams70 » Mon Mar 16, 2020 3:14 am

The high pressure pumps you buy generally have the oil filter bypass valve location blanked off with a plug whereas the standard pumps come with the valve still in place. The spring you can see in the pump body facing directly toward the underside of the filter is part of the bypass valve assembly. If you don't see this then most likely it is a high pressure pump.
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PostPost by: Davidb » Mon Mar 16, 2020 3:49 am

Thanks Rohan, thanks 2Cams.

There definitely is a pressure relief valve and spring. I will borrow a Snap On gauge tomorrow and check the pressure with that and report.
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PostPost by: 2cams70 » Mon Mar 16, 2020 4:02 am

Davidb wrote:Thanks Rohan, thanks 2Cams.

There definitely is a pressure relief valve and spring. I will borrow a Snap On gauge tomorrow and check the pressure with that and report.


Note the oil filter bypass valve is a separate component to the pressure relief valve. Both standard and high pressure pumps have the pressure relief valve but usually the high pressure pumps don't have the oil filter bypass valve. The oil filter bypass valve is only there to allow oil to bypass the filter should it become blocked. Unlike the PRV it doesn't regulate the oil pressure as such
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PostPost by: Craven » Mon Mar 16, 2020 11:31 am

High pressure oil pump supplied by Burton states pressure set to give approximately 65 psi.
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PostPost by: Davidb » Mon Mar 16, 2020 3:38 pm

Thanks for that Craven.

My concern is that the filter or its O ring could get blown off by that much pressure. Plus the stress on the gears of course.

One thing that occurred to me at 4.00am: I used Vaseline to prime the oil pump-I wasn't sure how long it would be sitting-could that be blocking the relief valve I wonder?
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PostPost by: nmauduit » Mon Mar 16, 2020 4:20 pm

did you run the engine long enough so that it gets a chance to heat to operating temperature? if so any vaseline blockage should have gone by now.

If inded the pressure is 80psi while all the rest is good, my main concern would not be immediate gear failure, but rather oil spill or accumulation, or possibly a weakness in a gasket being pushed out soimewhere. Before taking apart the oil pump I would try to let the engine warm up slowly (not revving it up), monitoring the gauge and leaks - and statically (make sure the oil filter is nicely tight) - 80 psi is high for road use, but not crazy high so that this warm up represents a mechanical risk just from overpressure.
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PostPost by: Craven » Mon Mar 16, 2020 4:54 pm

This worries me a little,
“ I did what I usually do-used the gasket as a guide to matching the inlet and outlet ports of the pump to the block ports to maximize flow using a Dremel grinder.”
You must have stripped the pump to ensure no particles were left possibly jam the relief valve, did you reassemble correctly?
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PostPost by: Davidb » Mon Mar 16, 2020 5:11 pm

Thank you gentlemen.

Nmaudit: I have not started the engine yet-I jave just cranked it over with the plugs out-this was just my first test yesterday. I just tried it again this morning and there is no difference. I am considering changing the 20/50 I put in for some 5/30 and see what that does.

Craven: I stripped and blew out the pump with compressed air before fitting it.

I may try refitting the old pump.
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PostPost by: Davidb » Mon Mar 16, 2020 7:13 pm

OK, as you were!

I just checked the pressure with a borrowed professional gauge and it is 58 psi.

I need a new oil pressure gauge!

Thanks for the responses.
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PostPost by: oldelanman » Tue Mar 17, 2020 7:47 pm

Davidb wrote:OK, as you were!

I just checked the pressure with a borrowed professional gauge and it is 58 psi.

I need a new oil pressure gauge!

Thanks for the responses.


Isn't that still higher than expected pressure for a standard pump at cranking speed ?
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PostPost by: Davidb » Tue Mar 17, 2020 8:40 pm

Apparently it is although the pressure is what I had when I built the engine three years ago and checked it with a stand-alone gauge. I am thinking that once the engine has run a bit and the vaseline washed out of the pump (it must be sealing it quite effectively) the pressure will drop a little.

Right now I am replacing the front control arms in my Volvo XC70 and waiting for the Ibuprofen to kick in...
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PostPost by: rgh0 » Wed Mar 18, 2020 6:48 am

yes I would need pain killer if i had to work on a Volvo also :lol:

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PostPost by: nmauduit » Wed Mar 18, 2020 8:41 am

if I may, Ibuprofen is not a molecule to be used lightly these days (tends to increase the risk level and complications of sars-cov-2 symptoms)
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