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MG MG Y Type - Bell Housing

I read in LTBYs that there are two distinct bell housings.

The first designed for the 7 1/4" clutch which used the 5/8" fork shaft.

The second slightly larger to accommodate the 8" clutch with a 3/4" fork shaft. This housing has reinforcing webs at the shaft housing and reinforced bolt flanges at the upper bolt holes.

I also read that they are not interchangeable.

I have two bell housings one with the reinforcing webs at the shaft housing and one without. Both have the reinforced bolt holes yet both have the earlier 5/8" shaft.....

My query is... what is the dimension that varies that makes the early and late versions non interchangeable....

And what about these possible 'crossover' types....can I use either as they both have 5/8" shafts?

I have attached a photo

Rob

Rob King

The bell housing for the YB and later TD accomodates the 8 inch clutch and has a 3/4 in cross shaft (where the release bearing sits)...ignore the reinforcing of the casing... that was introduced because of cracking in early ones and may not be associated with the change in clutch size from 7 1/4 to 8 inches. You can use a later YB bell housing with the 7 1/4 in clutch but it throws out the alignment of the release bearing a bit. If for instance you have an engine with a 7 1/4 in clutch but use the later YB (8in) bell housing themn you have to alter the length of the clutch rod to get it to work properly. This is the case on my car..and also Neil Cairns (or so I am told).. it works but not as well in my opinion as if you used the earlier bell housing with the 5/8 cross shaft. Better if you have a YB/later TD bell housing (3/4 in cross shaft) to use the later flywheel and clutch (8 in) or if you have the 7 1/4 clutch and associated flywheel to use the bell housing with the 5/8 cross shaft. As Michael Caine used to say ..'not many people know that'.
D MULLEN

David,

Thanks for the reply.....

Although I have two different castings they BOTH have the 5/8" shaft....

So can I use either without the adjustment to the clutch rod?

Rob
Rob King

Which clutch do you have? The 7 1/4 or 8 inch?

Willem van der Veer

The 8" clutch is deeper from front to back, so the centre line of the new 3/4" operating shaft was moved back 7mm compared with the 5/8" shaft. The earlier bellhousing can be used with the larger clutch, but the inside bosses, that house the operating shaft bushes, need to be ground away to clear the larger clutch. The clutch operating rods would probably need adjustment as the arc of travel of the clutch operating fork will change. The other alternative of using a later bellhousing with a small clutch has the problem that operating fork goes well over centre and the carbon thrust bearing and the mating ring on the clutch do not operate correctly - there is too much downward movement of the thrust bearing.
R A WILSON

Rob with the 7 1/4 clutch you can use a bellhousing that has the 5/8 cross shaft. On my car a YB I have a 7 1/4 clutch with the later 3/4 cross shaft bell housing - does this explain why I have trouble with operating the clutch etc..comments please?
Perhaps rob Wilson can e mail me.
D MULLEN

I have the 8" clutch with a modified 7 1/4 bellhousing, and haven't had any problems.
Willem van der Veer

With the small clutch and later bellhousing, the operating fork and carbon thrust bearing have to swing much further forward, another 7mm, before they engage the clutch mating ring. They then have to actually operate (disengage) the clutch, and the thrust bearing is starting to arc downwards as well as move forwards. If the face of the clutch ring has a groove worn in it that can cause problems, as the carbon thrust bearing is being asked to climb up the side of the groove. Also there is the possibility that the top face of the hole in the centre of the carbon thrust bearing will hit the first motion shaft - this could depend on how far the clutch pedal is pushed down (although the problem becomes less acute as the friction plate wears down). Filing or grinding a groove at the top of the hole may ease this problem, but this is only a suggestion. Perhaps better to look for a later flywheel and use an 8" clutch (may also need a later starter motor).
R A WILSON

Here's a picture of the modified bellhousing (yes, it's rather oily). It has the cut-outs in the inside bosses that RA Wilson describes.

Willem van der Veer

I have now checked two later 3/4" shaft bellhousings, and they both have similar machined cut-outs in corresponding positions - I do not have an early bellhousing, but I think the cut-outs are probably original. It must be that some 8" clutches will fit inside an early bellhousing without additional clearance.
R A WILSON

This thread was discussed between 20/06/2013 and 22/06/2013

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