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MG MGB Technical - 5 speed conversions

Its all a bit new to me as its my first MGB after running a frogeye for many years so bear with me.
Its a 3 speed syncro car made 1963 with a 3 main bearing engine, can i drop gearbox out from underneath and fit the 5 speed conversion or is it an engine out job.
If at a later date i change the 3 main bearing engine for a 5 main bearing engine will i have to alter the tunnel as is it the later starter that causes the problem.
What else would need changing if i change to 5 main bearing engine onto a 5 speed conversion designed for a early engine .

Thanks Roy
R Mcknight

The Ford type 9 fits an MGA tunnel so I'm sure it will go inti a 3 sychro MGB, you can check here

http://hi-gearengineering.co.uk/

This conversion is a joy especially if you choose the longer 1st gear. Personally I prefer the character of the o/d on my MkI MGB even though its harder work and the car is slower. For a daily driver I would go for the 5 speed. I think the bell castings are different for 3 and 5 main bearing engines. Again for an early car (is it a pull handle?) I would be inclined to keep it original, the 3 main engine is perfectly adequate and a bit faster with less internal friction.
Stan Best

It's an engine out job. The trans will clear the tunnel, as mentioned above, but the crankshaft pilot bushing is smaller on the 3 main engine, than it is on the 5 main engine, and will require drilling out to match the input shaft of the 5 speed trans. The 3 main and 5 main engines also use different flywheels. RAY
rjm RAY

Hi Roy,

I've done a 5 speed conversion, albeit on a 5 bearing engine, and have updated the article I was working to. If you would like a copy, send me an email so I can forward it.

Herb
Herb Adler

Echo Stan's thoughts on the 3 bearing.

Every factory racing MGB ran a 3 bearing engine, even after these engines were out of production. When they can be tuned up significantly and then thrashed around Le Mans for 24 hours why would you want anything else?

John.
John Prewer

I didnt know the 3 bearing was kept by special tuning, but it makes sense. I knew from Bill Blydenstein that all things equal the 3 main bearing engine was quicker. Brain Moylan says that at Le Mans if they could just qualify the B they were sure of a class place as the MGB may be uncomplicated, but its effective.
Stan Best

Dear Herb, May I please have a copy of your 5 speed conversion write -up? Thanks Mike
mike@quaysdentalpractice.com.au
J.M. Doust

Hi Mike,

Copy forwarded.

Herb
Herb Adler

This thread was discussed between 11/02/2011 and 16/02/2011

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