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MG MGA - Adjusting engine oil pressure?

I have a modified 18GB (5 bearing) engine in my MGA. As part of an engine overhaul I am re-seating the oil relief valve and thought I would boost the oil pressure a little. My new relief valve has a 3" spring and the standard poppet valve (Moss 460-155). Our local supplier says the packing piece (Moss 460-165) that increases the pressure on this engine is no longer available. Do people normally put this extra packing in or just run with the pressure generated by the spring alone. I see Barney (MGAguru) advises that 1/4" spring washers can be used to add about 6 psi for each washer (.060 to .070 thick washer).
Any comments?
Mike Ellsmore

Just curious as to why you need even more oil pressure?
On "B" engines, with all in good condition, you will get 65lbs+ cold, and 55+when warm...
On newly rebuilts, you can get 70lbs+ cold and 60+ warm.
Edward Wesson 52TD

Thanks Edward - I pulled my engine down after a cam follower failure - prior to that oil pressure when hot at idle was just below 40 psi. Rod and main bearings were in good condition (plasti-gauge clearance tests showed clearance around 0.001 - 0.0015" - only one rod and one main tested). As I found there was no packing piece between the spring and poppet as shown in the Moss catalogue for the GB engine I thought bringing it back to standard (increasing the oil pressure a bit) would be a good idea. Another issue is I have a big low oil pressure warning light mounted above the windscreen (coupe) that comes on at idle after spirited driving and I would like to keep it off! I reckon 5 psi would do it.
Mike Ellsmore

Mike, if the oil pressure is low, it will be due to wear and clearances in the mains, big ends etc. Raising the relief pressure setting won't help this situation, surely?
Art Pearse

Art I agree low oil pressure is a result of the clearances and I am addressing this with new rod and main bearings - I am also putting in a new oil pump. My query is should I put the equivalent of the OEM packing piece in now before I know what the operating pressure will be with the rebuilt engine. My guess is that adding this piece will boost the operating pressure by about 5 psi and ensure I don't have future problems with my oil pressure warning light until the bearings really are worn.
Mike Ellsmore

You can always put it in later if you want more pressure.

M Wellard

I have experienced the same failure twice. My oil pressure is 55-60 psi at idle and 65 psi at speed. I have changed to an oil with high levels of zddp (zink and phosphrous). What oil are you using? Oil for modern engines do not protect the cam and lifters in these old engines like the older oils did. They have been modified to protect the catalitic converters in modern cars. Unfortnatly the oil manufacturers did not warn us of the changes in their oils and what it could do to older engines. I just kept buying the same oil I always used for years, not realizing that it was no longer the same formula.
Ed Bell

Ed, I plan on using Rotella T 15W-40. It is for diesel engines, but has the zddp.
Art Pearse

I'm trying to relate cam follower failure to oil "pressure". I can't get there.

I highly recommend the ZDDP oils or additives.
Chuck Schaefer

Chuck, I understand Ed is saying you can have good oil pressure but still have engine failures - because of oil quality not quantity.
I have been using Penrite HPR30

I am changing to Kendall oil on the recommendation local engine rebuilder/speed shop.
Mike Ellsmore

Mike Kendall has a good name but Penrite has the highest percentage of ZDDP. I use Penrite Classis Light in my supercharged B which has 1800 PPM. On my recent rebuild the cam ,lifters and crankshaft were as new. Denis

Thanks Denis - I will quiz them some more.
Mike Ellsmore

Mike, the 18GB had a spacer. Buy the correct spacer and stick it in and leave it at that.

I saw one guy force non-stock washers in there and it seemed fine - until it seized in the bore as the cup had slightly expanded. Possibly a one shot bit of bad luck, but why take any risk when the proper shim can be had cheaply?

BTW, oil pressure isn't nearly as important as the volume going through the system.
Bill Spohn

This thread was discussed between 22/05/2013 and 29/05/2013

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