MGB Oil Leak Rear Head Gasket

[malcolm]

It's not really a R4 :smile:, it's the MGA I have fitted with a 1950cc tuned and fiddled with MGB engine.

I changed the head gasket last year because of a big oil leak from the rear of the engine. That fixed it, but it's back again after 300 miles. There are no other head gasket problems at all, just a leak from the oil feed to the rocker gear at the rear of the engine leaking through the head gasket.

I think the oil pump/relief spring might be the "uprated" ones as oil pressure is 70psi on the gauge.

I'm guessing pull the head off again and getting the block and head checked for flatness would be the way forward (or alternatively fit an oil catch tray). Has anyone come across this sort of thing before? I've had had head trouble in the past but never just an annoying oil leak - the engine seems fine otherwise.

For a bonus point, are cold plugs any use for tackling pinking at 2000rpm at light to medium throttle? Both the MG and the Gordini are a bit sensitive.

 

[Cornish4]

Hello Malcolm, I think you have put your finger on the reason for the problem, and a skim of the head and maybe also the block is required. Hopefully just the head will do the trick. The oil pressure is a touch high, even for a modified engine don't you think, 50 psi would be better, and you should be able to bring this down. It sounds like a nice car, Ive always liked the lines of the MGA, especially the coupe. I've had a few MGs over the years, from a 37 VA to a 76 BGT. My last British sportscar was a 79 TVR 3000M, which I sold a few months ago. Regards Brian.

 

[angel]

70 psi with the oil not up to temperature, and a rebuilt/good condition engine is not uncommon on th B-series.

Are you installing a good quality, known brand head gasket? I had had some similar kind of problem on an A-series (leaked coolant on the head gasket joint, before the engine had even been fired up), and on a Peugeot 204 (oil leak just like yours). In both cases the gaskets were of suspicious quality, when relpaced with qood quality ones, no more leaks! I linked the problem to the "fire rings" of the head gasket not compressing enough upon tightening, so that the rest of the gasket could not seal properly.

 

[malcolm]

Thanks Angel - I think you are right. I also had some coolant leak from the side of the head after loosening the bolts 1/4 turn, so the coolant is also too close to leaking.

I'll try another gasket from a specialist. Tempted to fit a standard oil pressure relief spring too - I think this one was "uprated" by the people who built the engine, but there's no need for higher pressure than standard.

 

[Steve Hennessey]

Malcolm, if you had a coolant leak after loosening the bolts 1/4 of a turn tells me that the head was not torqued down enough. Can I suggest that you get the head checked for straightness anyway, fit the best gasket that money can buy and torque the bolts down to the maximum allowed - maybe even to go as far as buying new bolts. After 500 miles re-torque the bolts by loosening one turn and then tighten. Repeat again at 1000 miles.

If you haven't removed the head yet why not try a retorque to see if it solves the problem? You have nothing to lose.

 

[mike4gtl]

if its pinking dont skim it, it will make it worse unless you retard it

 

[malcolm]

I got a bit further on the pinking - it needs backing off at 2000rpm for the pinking, but running just off idle is better when the distributor is more advanced. Reckon it's just wear in the advance springs/weights. Tempted to go for the 123 system, but that doesn't have a curve for a 1950cc engine with a hotter cam. I think the program it yourself systems need a timing ring on the fly wheel.

 

[mike4gtl]

You can buy the springs still from 'distributor doctor' Thats where i got the ones for my series land rover with a lucas 25d dizi