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oil pressure

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Diane Avatar
Diane Diane Linsell
melbourne, victoria, Australia   AUS
I have a 1968 MG Midget 1275 - at idle and 800rpm my oil gauge reads 80 lbs and engine warm. I am using Penrite classic medium oil, if I use a light oil will that bring the oil pressure down? with outside temperature at 112 degrees F.
Thanks

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bev sleet Avatar
bev sleet Bev S
Raunds, Northamptonshire, UK   GBR
use 20/50 weight oil , the higher the oil pressure the better, you seem to have a good engine at 80 lbs and 112f

S1 Elan Kurt. Appley
Akron, Ia., USA   USA
Yes, A series engines are supposed to run higher oil pressure than is common. if you wish, lower viscosity oil wouldn't hurt you but may be more prone to leak or have it consumed.

Kurt

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dickmoritz Avatar
dickmoritz Platinum Member Dick Moritz
Philly 'burbs, PA, USA   USA
A series engines are supposed to run higher oil pressure than is common.

Kurt, can you explain/elaborate?

Dick




In reply to # 3890659 by S1 Elan Yes, A series engines are supposed to run higher oil pressure than is common. if you wish, lower viscosity oil wouldn't hurt you but may be more prone to leak or have it consumed.

Kurt



Errabundi Saepe, Semper Certi
(Often wrong, but always certain)

ice Avatar
ice Gold Member Larry Ice
Lawrenceville, GA, USA   USA
Diane, Guys, seems like 800rpm and warm engine with 80psi is a bit much. What is the PSI at 3000rpm? Might check your oil pressure gauge against another oil pressure gauge. Most owners desire more psi for their cars but you have the opposite. A bit more background on the car would be helpful.

Diane, I see that you put the year of our car in the text but it would be super for everyone if you would put the car year into your profile so the year would automatically show on every post you make. Takes but a moment and you're done with it.



Iceman

Atlanta GA

60 AH MK1
62 AH MKII
67 Midget
71 Midget

S1 Elan Kurt. Appley
Akron, Ia., USA   USA
In reply to # 3890883 by dickmoritz A series engines are supposed to run higher oil pressure than is common.

Kurt, can you explain/elaborate?

Dick




In reply to # 3890659 by S1 Elan Yes, A series engines are supposed to run higher oil pressure than is common. if you wish, lower viscosity oil wouldn't hurt you but may be more prone to leak or have it consumed.

Kurt

Yes, I should have been clearer. When I was growing up around US vehicles and British Vehicles the British vehicles always ran far higher oil pressures. Maybe the American vehicles were just more worn!winking smiley

dickmoritz Avatar
dickmoritz Platinum Member Dick Moritz
Philly 'burbs, PA, USA   USA
Thanks, Kurt. I misunderstood your original post and thought you were suggesting that A series engines ran higher oil pressure than B series engines.

My experience agrees with yours, that older American cars ran lower oil pressure than British cars, perhaps because most all were six or eight cylinders, thus having more rod and main journals where oil/pressure could escape...

Dick



In reply to # 3892000 by S1 Elan
In reply to # 3890883 by dickmoritz A series engines are supposed to run higher oil pressure than is common.

Kurt, can you explain/elaborate?

Dick




In reply to # 3890659 by S1 Elan Yes, A series engines are supposed to run higher oil pressure than is common. if you wish, lower viscosity oil wouldn't hurt you but may be more prone to leak or have it consumed.

Kurt

Yes, I should have been clearer. When I was growing up around US vehicles and British Vehicles the British vehicles always ran far higher oil pressures. Maybe the American vehicles were just more worn!winking smiley



Errabundi Saepe, Semper Certi
(Often wrong, but always certain)

ice Avatar
ice Gold Member Larry Ice
Lawrenceville, GA, USA   USA
I think in general oil pressure for us cars wasn't as high as our English cars but I had a 62 Vette that had a 327ci engine. It. At the time it was a pretty hot car and prob could hold it's own now. It put out 340hp, had solid lifters, high lift cam, different heads and some other goodies. It's oil pressure was 60psi running down the road and it idled at 40psi. I'm sure the 327ci fuel injected engine for 62 has the same oil pressure as well, maybe the 300 hp also? The 300ci engine had hydraulic lifters and a lower red line though so maybe it had lower oil pressure. I never remember driving one of them.



Iceman

Atlanta GA

60 AH MK1
62 AH MKII
67 Midget
71 Midget

Sprite1956 Roger Parry-Jones
Melbourne, Victoria, Australia   AUS
Diane,

I believe you have excessive oil pressure, especially at idle, considering engine operating temperatures in our recent heat wave and assuming it is not a completely newly rebuilt motor. Oil pump type, bearing clearances and pressure relief valve spring are the main factors in oil pressure readings. A long time ago I rebuilt a race 1275 and used Penrite 50 race oil (perhaps before the motor was fully broken in). I had 50 psi oil pressure at (engine hot) idle and 80 psi at full noise. Due to the thick oil and high compression ratio, I used to pull the spark plugs and spin the motor over to get the oil pressure up before replacing the plugs with 'hot plugs' to start the engine. Once the engine was warmed up I would replace the plugs with 'cold' race plugs. What a hassle! The next oil change I used a semi-synthetic 20/50 oil which resulted in oil pressures ranging between 25 at idle and 60 at full rev's. I never got those original high oil pressures again with that motor but that was fine. The engine started easier, ran fine, didn't lose pressure when it was hot and the oil pressure was perfectly within specification. I never went back to 'classic' single rated race oil again and never had a problem. For what it's worth, excessive oil pressures do cost horsepower due to frictional drag. Oil pressures of 20 at idle to 60 psi at say, 3000 rpm (engine hot) are perfectly acceptable.

Back in the day, we used Cooper S rated oil pressure relief springs. The standard white metal spring seat plunger (which would leak pressure at its seat when worn) would be replaced with a ball bearing which never wore out and would also increase spring tension, thus increasing pressure seen at the gauge. (Rarely the standard plunger would wear enough to kick a little sideways off it's seat and oil pressure would plummet. Sometimes they would even stick in the spring bore and cause oil pressures such as you have.) Perhaps someone's done the same on your engine? If so, I'd suggest you: A. change your oil to one of the proprietary 20/50 multigrades, B. check your oil pressure gauge against one that is known to be accurate, and C. check your oil pressure relief valve plunger. In one of these moves you will find the answer to your apparent excessive oil pressure. Joining the MG Car Club or the AHSDC (Austin Healey Sprite Drivers Club) might be helpful too.

I'm off sailing and camping at the Gippsland Lakes for a few days but I may be able to assist you next week, if you don't resolve your questions.

Regards,

Roger

mgm1967 Avatar
mgm1967 Silver Member Mike Melton
West Memphis, USA   USA
Does your car have a mechanical gauge? Is it a stock gauge? If it is an electric gauge, determine if it and the sender are good. Did this problem happen all of a sudden?

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