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MG MGB GT V8 Factory Originals Technical - Oil Leaks

1974 MGB ? rover 3.5 Conversion
Two Oil leak problems

1) I rebuilt and installed the Rover 3.5 into my B last winter, over the course of the summer I had an oil leak from the rear of the motor. I replaced the pan gasket several time to no avail. I then pulled the engine and replaced the rear cam seal and it still leaked. I replaced the rear main rope seal with a neoprene one. When I purchased the neoprene seal I was told that it was very hard to install while the motor was in the car, I didn?t have any problem and the seal went in very easily. Unfortunately because I had put the seal in backwards it still leaked, I finally got the seal in properly (replacing the pan gasket yet again) and it still leaked. I put in a PCV valve and that seemed to solve the problem. But the car went of the road within a few days.
The car has sat for 2 months now and I just started it up today. Once again there is a huge pool of oil under the tranny, I know where it is coming from, the rear main seal. Any advise on how to stop this leak would be appreciated. I am wondering if I might have ruined the gasket by installing it backwards. I am also wondering if maybe by some off chance (Purchased from a V8 specialist) the seal could be the wrong size, but they are suppose to fit both the Buick and Rover.

2) When I started up the B today I also noticed another oil leak, this is on the front of the motor on the passengers side where the intake, head and block come together. It looks like the oil is leaking from the head. (Oil trail starts a couple of millimeters back from the intersection of head/block/intake) I have re-torqued the head bolt on the end of the head a couple of extra pounds as I know there is a oil journal at that end of the head. But it still leaks. The heads were planned/milled prior to installation. Should I replace the head gaskets?


I have had some of the same problems my self. I finally pulled my engine (not so hard) and then disassembled it to get the seal upper half in without the crank in. I too am using D&D's seal kit. When I pulled the crank I noticed that the silicone sealant that was injected into the bearing cap grooves had not cured (after two weeks). But I don't think the rear seal was the problem of my leak. The leak was simply too much too quickly. I could pump out a half pint of oil in twenty minutes. My rear cam plug was not leaking. I think what was leaking were the two oil gallery plugs at the rear of the block. I pulled these and reinstalled with permatex. I have not yet run the engine but have pressurized it with a drill motor to the point were the pressure relief valve opens (50 psi on the mech gauge) and there are now no leaks. The real test will be running the car several times to heat and cool the block. I hope this helps you out.
James Johanski

James- interesting point about the oil pressure relief valve's setting. I've just acquired a 90 deg offset oil filter base from a Buick 300 engine and I was wondering what the relief pressure should be for the valve- is 50 psi the norm for the 215 engine?

I believe 45-50 psi is about what the relief valve is good for on a 215. It may be higher on the 300. It was higher due to a stiffer spring on the original BGTV8. The old V6 oil pump base had a higher setting also I believe. All of this does not make much difference as the engine lives well with about 35-40 psi and sufficient volume (good pump and no blocked passages). You can upgrade the pump with a Melling high volume kit which consists of a spacer plate to allow the use of deeper pump gears and a higher pressure spring. You can also add a V-6 pickup and drill out the galleries for more volume. All of these tips I have gotten from Dan LaGrou at D&D. He really knows more about these engines than anyone. Dan not only has the answers but can sell you the parts right off of his shelf. His prices are reasonable (competitive with any other source) and his service is excellent! He has done more through his free advice for MG V8 convertors than anyone.
I don't work for Dan nor have any interest in his business, but I think that he should get credit for all the help he has given me and others.
Also, Dan has the the lip seal kit (he invented it) available. It works quite well if installed correctly.
I know this because I have installed three of them so far. The first two were removed because I thought that was the source of my leak. When I removed those seals, the first one in the car and the second one with the engine removed, I found no evidence that the seal was the leak source. This is true even on the second seal where the silicone had not fully cured.
So in conclusion--1. Check all of the plugs for possible leaks before blaming the seal--Remember a seal unless it is trashed will only permit a slow leak, while a fast leak is due to a pressure point finding its way to atmosphere, as in the case of the rear galley plugs. 2. The engine does not need a lot a pressure to live--it needs volume.
Here's to good luck and no leaks for us all!!!!
James Johanski

There's an oil gallery between the block & the timing case that shouldn't be overlooked. If the paper gasket between them is damaged, oil can escape , also oil pressure can suffer.HTHs Barrie E
Barrie Egerton

Yup I too use a drill to run the oil pressure up and prime the engine when I first rebuilt it and it didn't leak. After replacing the oil pan gasket several times it didn't leak either, only after running it for awhile at higher RPM (3000+) did it leak. I am going to give D & D a call tomorrow and see what he has to say, if the engine has to come out that's fine, it was in and out several times while I fitted the engine and then again last summer, so since it's off the road for the winter it is not that daunting.
The other day when I ran the engine I let it come up to temperature and then ran it up to 5500 a few times, let the car idle for a while and keep checking under the car, no problem, shut the car off and then took a look, at least 1/2 cup was now on the clean floor. Makes me wonder if while it's running it's fine (now with the addition of the PCV valve) but when I shut it off the carb is no longer working the PCV valve and enough pressure builds up in the crank case to push out the oil through the rear bearing?
Please keep me informed of your progress with this problem.

I replaced the timing chain to block gasket last summer, but the other day when I started up the car I could actually see the oil starting to leak just about 1/4" down the head-block. All I can think of is the head gasket?

Well I started up my Rover 3.5 again today looking for oil leaks again. I checked to make sure the PCV valve was secure, not so sure it was totally secure last time??? And the vent at the rear of the engine into the lifter gallery was clear, I have the rear end up on blocks so left that way and started the car, ran it up to normal operating temperature and checked under the car, so far so good, no leaks, ran it up to a sustained RPM of 3800 for a few minutes and checked again, so far so good, no leaks. Keep the car running for a while and still no leaks, well the very odd drip (but this could be old oil that is just draining off the engine, remember it has been leaking for awhile from the rear seal, rocker cover gasket and the front of the engine). Shut the car off and checked again, no leaks.
Dropped the car back onto the ground and repeated again. No leaks. Shut the car off and no leaks.
It?s got me mystified? All I can think of doing is trying it again. .

The leak at the front of the engine is actually coming right where Dan at D & D said it would be. Right where the intake, head, timing cover meet. It is leaking from the intake rubber gasket right at the very corner. The question is can I shoot some silicone into there and solve the problem or do I have to remove the car/intake and gasket and then replace all?

Hi Bruce,
My BV8 has always had oil dripping from the hole in the bottom of the Rover bell housing, and a bit from the front seal. Dan told me that unless a person really knows what they are doing when re-assembling these engines, oil will leak past those little crucifix seals in the rear bearing caps - so I just let it leak.
Its been 6 years of trouble free motoring though!

You have much patience!!


Hi Bruce
After numerous attempts to stop similar leak problem i gave up and learned to live with it, it is not that big of a leak, about the size of a quarter dollar or so, i just keep on hosing off the garage and the under side of the car.
This is in my '63 Skylark, My MGB/Rover has not developed this bad habit as yet.

Just a tip for anyone rebuilding a Rover V8 - don't use the crucifix seals - just inject a non setting gasket sealant (Hylomar) into the gap after seating the cap.

Generous use of sealant is required on all gaskets and housings if oil leaks are to be avoided.
Chris Betson

This thread was discussed between 05/01/2002 and 13/01/2002

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