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MG Midget and Sprite Technical - Cylinder block side covers

It's 50 years since my first A-Series engine and oil leaks from the side covers have always been a problem. On my current 948 block I have tried every solution I can think of. The front cover is the 1098 one as I am using the closed-circuit breather. With the standard rubber gasket the oil separator fouls the engine front plate so I made an aluminium spacer which is fitted with paper gaskets and silicone. The rear cover is another 1098 one which uses the rubber gasket. I found that when tightened to correct torque the gasket slipped out, so I welded a rim onto the cover to stop that. I use the little rubber seals round the bolts. All this worked well for a year or so, but now it's leaking again. I have just re-done all the sealant, which I left to cure before going for a run, and of course they both still leak. Is there some really clever solution that I haven't thought of?
L B Rose

Buy a 1500? :-D
Malcolm Le Chevalier

The gasket contact area may not be parallel to the block. This could happen from over tightening by a PO. Lay them on a flat surface to check for warping. Are you getting enough ventilation to relieve crankcase pressure?
A 1275 would also solve the problem.
J Bubela

As I said, I have the 1098 closed circuit ventilation, with extra vent pipe from the redundant fuel pump point. Rocker cover cap also vented. Compressions all excellent, so I don't think blow-by is a problem. I'd have thought that the rubber gasket would deal with any minor warping, but I'll check.

L B Rose

What about fabricating replacement side covers from 3/8" aluminum or 1/4" steel plate?
Stan Kowznofski

As I said, I have the 1098 closed circuit ventilation, with extra vent pipe from the redundant fuel pump point. Rocker cover cap also vented. Compressions all excellent

When you say vented.... where to and how? Outside to the atmosphere? , you have to keep the engine sealed so the only air comming in is thur the air filters and the pin hole in the valve cover cap...any place else air can get into the engine needs to be capped off, or else you loose engine vacume, then you get ither nuetral or positive sump needs neg pressure to hold the oil inside the engine

Another not.... letbthe silicone set up about 75% before you torque it down.... if the cure time is 4 hours dont torque it till 3 hours otherwise it will simply push the silicone out of the way
1 Paper


I'm not sure it applies to the A-Series, but on a B-Series in my MGB, I have not had good luck with the rubber/silicon gaskets. The problem was only on one of the covers, but I forget if it was front or rear. I had better luck with the cork gaskets. The rubber one wanted to slide out of place.

C R Huff

The rubber gaskets were originally made for the covers which have a formed groove for them to sit in. They are a different size from the covers which take the cork gasket. If it is no-groove cover, rubber gaskets will need to be stretched to fit and can move. This is made worse if any sort of sealing compound is used, as the goo acts as a lubricant.
To make matters a bit more difficult, there is a size difference between the covers and the hole in the block that means that the coverage of the gasket is reduced - so the covers have to be aligned properly. Not sure whether this last issue is an A series issue, it certainly is with the B series which used the same gaskets.

I get a 100% success rate as follows:
- Use the right size gasket; generally it is thin cork gaskets for the no-groove cover, and rubber gaskets for covers with a groove.
- Fit dry (no goo), always.
- Ensure proper alignment.
- Use the later B series bolt sealing system of cup washer and square section O-ring (12A1176, 12A1177).
Paul Walbran

I'm back folks! Been busy this last week renewing conrod small end bushes, but that's another story. In the process I found that the thin gasket on the front cover had slipped. Re-done with silicone and no gasket, and seems OK.

The venting goes to the inlet manifold via the correct 1098 gulp valve.
L B Rose

This thread was discussed between 27/09/2017 and 09/10/2017

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