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MG Midget and Sprite Technical - Calver/PM/MED Rear Seal
I�m in the process of fitting the rear seal kit as commissioned by Keith Calver and supplied by Peter May/MED etc. So as rear seal leaks seem to be a well discussed topic here I thought I�d post some photos and experiences of fitting it.
This being done as part of full engine rebuild so as the block needs machining it�s the perfect time to do it. Now I�m very sceptical of these kits having had bad experiences with the previous PM seal - from the Morris Minor Centre I believe. But I�ve been told by a few people that this new one does work so I�ve been persuaded to try it. When up I say try it, there isn�t really any going back due to block machining so it had better work! It�s also worth mentioning that the scroll seal hardly leaked! The block has now been machined by PM which basically means removing the scroll seal top cover and machining the lower half of the rear main cap perfectly flush to the block. Then 5 holes are drilled and tapped in the cap to hold the seal carrier on. The top part of the carrier bolts in the same place as the original scroll top cover. As the new seal runs on two areas of the crank that aren�t particularly smooth these need polishing up a little. I�ve been doing this tonight with some fine emery strips and seem to have got a decent finish. The areas in question are the rear face of the thin flange immediately to the rear of the main bearing journal and the 1/4� wide area at the rear of the scroll. I�ll post a few photos of the seal and crank etc. It will be a week or so before I actually fit it as the block is away having a some other work done. Photo of crank where polishing is required: |
John Payne |
Photos of seal:
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John Payne |
Photo of seal carrier:
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John Payne |
Something to consider, when assembling the rear main bearing, is that the Mk1 Workshop Manual says to put Wellseal between the rear main bearing cap (only) and block on assembly. The Mk2 Workshop manual says to use Hylomar. I don't have later Manuals, for later marks, but have used Wellseal on 1275. |
Alan Anstead |
I must be being dumb... will oil not just wizz through the big gap in the seal?! |
Malcolm |
I second Alan with the use of sealant on the rear cap. I used Hylomar and have not suffered oil loss from the rear main even with the original scroll seal. |
Bob Beaumont |
That looks likely to work far better than the others that run on the edge of the crank flange. In effect you are using a modern material to run the scroll seal with zero clearance as well as running on a small area of the face of the crank flange. Seems an eminently better solution apart from the machining required to the rear main cap. Rob |
MG Moneypit |
A pity this isn't available for small bore blocks. I have got the Morris Minor kit working better, but still not perfect. The crank machining should be cheaper than fitting a sleeve to the flange like I had to - twice, because the first one fell off! Malcolm, the gap in the seal closes up when the carrier is fitted. Same type of seal is used on C Series. |
Les Rose |
Thanks Les, not something I have ever played with. Couldn't quite see how it would work. |
Malcolm |
Yes, the seal has to be split as it sits forward of the flywheel flange so it�s the only way to get it on. The instructions say to place the split at the top and seal with a dab of silicone. It�s obviously a specially made seal and replacements are �40! |
John Payne |
Very interesting John Payne.
It doesn't really look like a conventional lip seal. Does it have a tension spring in the groove of the 'open' face? Anyway, given that it was commisioned by Keith Calver, who has a good reputation for knowing what he's on about, this looks like it might be a winner. He says it has "out-standing" results fitted to track cars. "Having tried all manner of methods to prevent oil leakage from the rear main of the in-line A-series engines, including the seal kits already on the market, I decided they were all a lost cause. Nothing worked well for any period of time on anything other than completely standard engines, and certainly not performance-orientated engines. I looked at some complex solutions that would make the kit very expensive. I wanted a solution that was effective and didn't cost the earth." https://www.calverst.com/webshop/sprite-midget/cst3002-rear-main-seal-kit-2-0-in-main-1275-only/ |
anamnesis |
Isn't the Mini rear main cap already flush with the block? Can you not use a Mini one? Rob |
MG Moneypit |
Finally managed to fit the crank and seal. It's a bit of a faff to fit but not as bad as the Morris Minor one. Basically you fit the housings to the block and cap, ensuring they are nicely central and using little sealant. Then fit the seal to the crank, with sealant on the join. Fit the crank with the seal gap at the highest point and then the main cap, again with sealant.
This is a competition engine with an open breather system. I'm fairly confident it will work but I'll try and remember to report in in a few months! |
John Payne |
This thread was discussed between 01/03/2022 and 11/03/2022
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