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MG MGB GT V8 Factory Originals Technical - can I fit an SD1 box to my old v8 conversion?

My problem is that I have a roadster conversion which was carried out about 1985 using an SD1 engine and the original MGB gearbox.
I'd like to fit an SD1 5 speed box - I've even acquired one - but I have just been told that part of the engine casting would have been cut away in the original conversion to allow the starter motor to be fitted to a special SD1-MGB gearbox backplate.

This means that I face the choice of putting up with the MGB box or sourcing a whole new SD1 engine-perhaps not worth it unless/until the present box breaks?
Another thought: what about folks who own factory built cars: are you in the same position or can you fit SD1 boxes some other way?
Steve
Steve Musgrave

I'm guessing (I've never seen one) that they would cut away the starter motor 'hole' on rear starboard of the block. Perhaps you could make an adaptor plate/bracket to locate the starter motor in the right position. Not easy though.
Peter

Steve.

Have you got an SD1 bell-housing with the gearbox ?.

From memory,the housing bolts directly on the SD1 engine (I can't recall having a backplate).

I don't know how difficult it is to replace the gearbox without removing the engine.....I believe it's been done, but I've always removed the engine and gearbox together.

Mike
Michael barnfather

Is it possible that the conversion included a MG V8 gearbox - they were freely available in the mid 80s ?

If the engine block is cut up you may want to keep your present kit - possibly get it refitted -

If your engine block is intact, you will need a RV8 or TR8 bellhousing (I believe the SDI version may be too bulbous) - you will then have a choice of the LT77 or Gentrag boxes - but need a new crossmember and propshaft.
RMW

TR8 bellhousing is identical to a SD1 same part no,
Russell

I am familiar with your setup, was talked out of using one like it in the early 80's as it was non-reversible, at least from a practical standpoint. IF you had the piece cut off the block, IF you had another engine block for a pattern, IF you had a really great welding technition who could also pre-heat the parts, you might be able to reverse the situation.

MG trannies are relatively cheap if yours is a problem. A different rear end ratio might make the car more drivable if you have the original 3.9 ratio. The V8 cars had a 3.07 set of gears, so 1st gear was usable. That might be your cheapest option.
Last, is a new engine, at least a short block.

Switching to a Rover tranny involves a new bell housing, clutch & pressure plate, clutch slave & mount, & you will need a new or modified drive shaft.
Typically, the shift extension housing has to be modified to have the shifter come through the tunnel at the correct location. Plenty of specialists where you are to do all that.

Jim Stuart
Jim Stuart

You'll also have to raise the front end of the gearbox tunnel to get the SD1 box in as it is taller, which is probably why your car has a B box in it. Aside from the other mods that have been previously listed, one of the starter motor mounting bolts on an original MGV8 block also doubles as a bell housing bolt so if the starter mounting flange is missing then what you gonna do?
Les Cole

This thread was discussed between 09/06/2004 and 10/06/2004

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