V8 Oil Leak

Technical MGB discussion
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V8 Oil Leak

Post by IanVFR750 » Sat Nov 14, 2020 12:48 pm

I'm new to the forum and I'm looking for any information you guys may have on V8 engines.

I have a 77 V8 roadster ( chrome bumper conversion ) which has had an increasingly bad oil leak from the back of the engine sump/gearbox area. I thought it was the sump gasket but have replaced this and the leak is still as bad ( even after tweeking up the sump bolts a little).

Does anyone know if there is a problem seal or gasket that causes leaks in this area between the engine and gearbox - a mechanic friend mentioned it was probably the crank seal but he admitted he was not familiar with Rover V8 engines.

Any info on this issue would be much appreciated.


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Paul Hollingworth
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Re: V8 Oil Leak

Post by Paul Hollingworth » Sat Nov 14, 2020 4:51 pm

First let me say that I've never owned a car with a Rover V8 but are you sure its not leaking from the rocker covers or the Valley cover in the vee (known fault with the engine).
Have you been on the V8 register website ?
I couldn't see anything specifically on oil leaks in their technical notes but you could ask your question on their bulletin board.
1971 MGB roadster & 2006 MGTF

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Re: V8 Oil Leak

Post by IanVFR750 » Sun Nov 15, 2020 1:37 pm

Hi Paul -

I've checked around the rocker covers but there is no sign of an oil leak in this area. I'm new to V8s so not sure what the "valley cover " is but I'll investigate that further. I'll also check out the V8 register.

Thanks for reply.

Simon G.
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Re: V8 Oil Leak

Post by Simon G. » Mon Nov 16, 2020 12:34 am

'Valley cover' goes across between the cylinder heads, under the inlet manifold.
+1 with Paul H's advice to move across to the V8 register forum!

Edit - should probably suggest V8 forum as well, plenty of Rover V8 knowledge there as well: https://www.v8forum.co.uk/forum/index.php


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Peter Cresswell
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Re: V8 Oil Leak

Post by Peter Cresswell » Tue Nov 17, 2020 2:19 pm

Like others on here, I don't have experience of the Rover V8 engine and you have already been pointed to the V8 register, but generally speaking from my experience, oil leaks from the area at the back of the engine originate from either the rear crankshaft oil seal or the input shaft oil seal to the gearbox. If the clutch doesn't slip, then this points to the crankshaft oil seal as the leaking oil runs down the back of the flywheel so doesn't get onto the clutch plate. If it does slip, then the oil is coming along the input shaft from the gearbox and so can get onto the clutch plate.
Most likely the cause is excessive crank case pressure which forces oil past the oil seal on the rear of the crank, and this is caused by engine wear.
Do you know anything of the history of the engine? How many miles has the engine covered (not the car!)? Was it overhauled before it was put into the MGB? Who overhauled it? Is is an early engine or a late engine (things like oil seals are likely to have been improved over the years during the manufacturing life)?
The V8 register are more likely to be able to help you with these questions but it would be a good idea to have the engine number to help them.
1969 MGB Roadster
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Re: V8 Oil Leak

Post by Bumpa » Mon Dec 14, 2020 12:22 pm

I wonder how old your V8 engine is? Early engines, such as those from Rover P5 and P6 had a rope type seal at the rear of the crankshaft which is a well known leak point. Later engines used a normal sprung seal, but these can fail too. The later seal doesn't fit the early engines.
1969 MGB GTV8 3.9 Conversion, 1977 Triumph Dolomite 1850HL, 1971 MGB roadster undergoing restoration.

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