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MG MGB Technical - Oil Pressure too high??

I have just started my 1973 GT for the first time in 18 months. She is going into storage so I can finish the V8 over the winter.

I rebuilt the engine completely, rebore, pistons, regrind etc. I also fitted a uprated Moss oil pressure relief spring and plunger.

When she started she ran at 80psi. After 1/2 hr, ticking over, water temp about N the pressure has only dropped to about 70-75psi.
I removed the rocker cover (all new rocker gear) and oil was gently dripping from each rocker)

Do I have a problem? I believe too high a pressure can cause problems. Should I replace the pressure relief with a standard version?

Regards
Dave
D M Tetlow

I am using Classic 20-50 Castrol.
D M Tetlow

Dave,

i also had the hugh pressure by fitting a competition oil pump and an uprated oil pressure valve ans spring assy. Readings were slightly lower than yours but this might result in the wight and quality of oil used. Within some K kilometers, oil started flooding the gauge and dripping from under the dash.
A softer spring inside the presure valve and no shim undernead it was the solution to return to normal oil presure and a new instrument has fixed the leaking problem too.

May be you should check the spring and, if also installed the washer, inside the valve and use a lighter one, before further damage is seen.
It is also recommended by some engine specialists not to go to far with the oil presure on th B-Series engine, as wear on the drive gear for the pump and dissy might cause further problems...

Ralph

Ralph

I've got a sticking pressure relief valve on mine and get 80psi all the time (the housing in the block is burred, and replaving the valve only half cured it).

When it started I thought it would turn the car into the Torrey Canyon (or Exxon Valdiz, depending on age group!) but to be honest I think it drips less oil since I started using the Halfords Classic than it ever did.

I do know that too high a pressure will stuff the gauge if it goes above 100psi....because I've done it twice.

Dave.
David Smith

Dave I wouldn't do anything until the car has been used for real, ie do a 20 mile run and see what the pressure is then.
If that's the first time the engine has been run since the rebuild I would be inclined to wait till it's done several hundred miles.
Ron
R. Algie

Thanks for your help Gents.
Dave
D M Tetlow

Try changing the oil and filter. There may have been a little swarf or debries from the rebuild that could have partially blocked the filter. It is good practice to first change the oil after a few hundred miles anyway, so i would just bring this forward.

Iain
67 BGT
I D Cameron

Dave. I am a little confused. You mention your 73 GT and V-8 conversion in the same paragraph along with the fact that the GT has a rebuilt engine. Basic question--what engine does the car under discussion have?

If we are advising on a V-8 engine, I believe there may be a problem, but cannot say without knowing which V-8 engine we are writing of.

If we are discussing a BMC B series four cylinder engine--good job, you did the rebuild right. Just had a chance to drive my daughter's car this last month as we were storing it for them while they were moving to their new house. Now, they have a garage and Daddy does not have to do all of the oil changes anymore. Some will remember that I rebuilt the engine some six years ago when she moved away to college and that she and her fiance (now husband) took several trips in the MG in the 1,500 to 2,000 mile range. Thus, a minimum of 25K miles on the engine, perhaps more. Oil pressure is a steady 80 psi on start up and runs between 70-75 psi at highway cruise. Drops to between 35-50 psi at idle after several hours of highway driving.

All of this is in line with my other rebuilds and what I remember of my purchased new 79 MGB when I owned it (5.5 years of ownership and 62K miles).

Iain is certainly correct--an oil change and different filter may have some minor impact on your oil pressure. But, all I am seeing is that you did a good quality rebuild--assuming this is a B series engine. Good job.

Les
Les Bengtson

Les

Thanks for your help. Yep it is a 18V 1.8 engine.

I will definitly do as Iain suggests, especially as when it turned over for the first time 18 months ago, there was no pressure. I had fitted the wrong gasket on the pump!!
I fired up the engine only for a few seconds then, so it looks as if I may have got away with it.

The V8 is another story. I am on the 3rd rebuild now. I will be bringing it over the the US next year for MG2008 and the V8 meet.

Regards
Dave.
D M Tetlow

Do Not Panic. I rebuilt my engine a few years back and got numbers a lot like Les' and though at first I had to tighten a few fittings there's been absolutely no trouble after driving it daily over many thousands of miles. Around 80 psi seems to be where the uprated relief spring puts it, and it's normal and harmless. Sure, there's no need for all that pressure, but if you're not pegging the gauge you won't destroy anything. Your pressure is high because you put a high pressure spring in, that's all. The spring has been tested and causes no damage. Worry not, and continue driving.

People worry so much about oil, and really, you just want the oil pressure to be above the minimum spec and below the max on the gage, and you want most of the oil to stay in the motor. That's pretty much it. If you've got that, you've built a good motor that will serve you well.

Relax, drive, and enjoy.
Sam

This thread was discussed between 14/11/2007 and 17/11/2007

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