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MG Midget and Sprite Technical - Gearbox mods for 7.5 inch clutch

I have a nice new engine ready for fitting. It has a Peter May steel flywheel and 7.5 inch clutch. I know that the standard midget gearbox has to be relieved to allow this to fit. I have some instructions but I wondered if anyone who has the same has any tips on how much material to remove (I don't want to trash a perfectly good g'box). I also read in Daniel Stapleton's book that there might be a clearance problem with the inertia starter - anyone know about this? Thanks in advance, Chris
Chris H (1970 Midget 1275)

Hi Chris

Have not fitted the PM clutch and neither do I have a standard box however I have recently finished my own 7.5 clutch conversion.
With that I did have the problem of the starter bendix interfering with the clutch cover.

I subsequently machined the cover to clear the bendix

It is easy to check if this will be a problem by simply mounting the stater motor to the backplate of your engine (On the bench) install the clutch and flywheel and turn the starter by hand to engage it in the starter ring. With it engaged turn the engine and check theat the clutch cover is clear on a complete rev. Mine was not, but as I said it was not a PM clutch.
Bob Turbo Midget England

I had the PM set up on my old race car. Just grind away the area around the closest bolt fixing for the steel cover that goes over the back of the starter. Do a trial fit and it will be apparent.
John Collinson

Hi John - yep, that was what Peter May said to do but a leaflet came with the engine suggesting that further work was required around the area of the slave cylinder bolts. I take it that was not the case for you? Chris
Chris H (1970 Midget 1275)

I've got a standard flywheel, lightened and fitted with a 7'5" PM clutch. Had two different ribcases on it and had to relief.......nothing. No grinding or anything.
Alex G Matla

I think this can depend on the make of cover. Years ago i fitted a Hillman Hunter 7.5" clutch to an Austin A40 Farina and had no problems with either relieving the OD of the cover or the gearbox case. Some years later talking to someone else they mentioned it was common to have to relieve the OD of the cover and/or gearbox. I guess I was lucky in my clutch cover choice.
David Billington

You'll need to do a test fit of the gearbox and turn the engine over slowly by hand. You may find that the new 7.5" clutch from Peter doesn't foul anything. I don't have a virgin gearbox or T9 bellhousing to check this.

I'm more confident that the new 7.5" cover doesn't need the starter bendix mod though I've used pre-engaged for some years. Assuming your flywheel and clutch cover look like this.

Daniel Thirteen-Twelve

If its made in England and says: "Bold-on job" its normal you need a grinder, plasmacutter, welder and sledgehammer.
But still, its a funny breed these English. ;)
Arie de Best

Ha ha Arie. Is it a typ-o or do you really mean Bold, as in "one bottle of shampoo lasts a life time"
Alex G Matla

..."eaflet came with the engine suggesting that further work was required around the area of the slave cylinder "
check this WITH THE SLAVE CYL BOLTS IN PLACE. I had to cut a bolt down as they protrude through to the inside of the bellhousing too far.
David Smith

Mine looks like this...

Alex G Matla

Dear All

Thanks for the advice - a bit of 'try it and see' seems to be called for. Daniel - my clutch and flywheel look much the same as the one in your photo (see attached picture). Although there are some minor differences I think this is the same bit of kit.


Chris H (1970 Midget 1275)

This thread was discussed between 22/09/2010 and 23/09/2010

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