Gearbox input shaft

[Cornish Wrestler]

Ive just started the task of swapping a non overdrive mgb gearbox for an overdrive one,simples I think, one in one out a few tweaks here and there a bit of wiring job done , but No , the old box comes out only to find the input shaft has been slimmed right down, buy the look of it by hand , file and grinder kind of job!! and on inspection there is some sort of roller bearing a bit bent and mangled in the end of the crank, any ideas please. Surely this should have been a mgb box to a mgb engine and there fore a straight swap , or was the marina crank different , i dont know what the engine originally came out of , only that its number starts 18v.
Thoughts and ideas would be appreciated

[Robert in Cumbria]

Re: Gearbox input shaft

It doesn't sound good, do you have a photograph?

Could the collapsed bearing have done the crude 'slimming down' of the spigot?

[b_caswell]

Re: Gearbox input shaft

http://www.mgcars.org.uk/mgcc/sf/990303.htm

A careful read of this may answer a question or two!

[dcunn]

Re: Gearbox input shaft

Look at the clubs "Roadster Tech Tips"....I seem to recall much useful info in there on this subject, and many people before you
have had this sort of problem

[stevejgreen]

Re: Gearbox input shaft

All Marinas fitted with 18V engines had sintered spigot bushes not needle bearings. But what you find in an MGB could be anything as Marina engines were commonly swapped into them as an upgrade path.

[lil_red_roadster]

Re: Gearbox input shaft

No prejudice in that article is there Ben...?! As for the comment that the Marina flywheel is bigger than the B...what cobblers. I have both and the MGB is 1" bigger & somewhat heavier.

Oddly Peter Burgess recommends the early Marina crank as being the best of the B series bunch...

Back to the original post...it is likely to be a Marina 18V engine...the MGB input shaft is a larger diameter than the Marina and will not fit. Some Marina engines may have been fitted with an insert in the crank (which can be removed and replaced), others (the majority?) were simply sized for the Marina input. Someone has obviously "machined" the MGB input in order to make it fit a crank it was never intended to mate with..!

[b_caswell]

Re: Gearbox input shaft

Jez, It seems these days you have to pick out the factual from the "I'm the expert" fiction on lots of these web sites. If it was relevant to Triumphs I would be in a better position to comment further.

My suggestion would be to get a bronze bush of a size that can be machined to fit. Don't recall coming across a roller bearing for the spiggot before, well not in BL cars!

[Cornish Wrestler]

Re: Gearbox input shaft

Thanks guys , it seems as suggested that it is a late marina engine with a drilling in the crank that was suited to the smaller input shaft of the triumph type gearbox, being a later crank it has no insert that was designed to allow either the crank to be compatible whichever engine it ended up in , so i've either got to strip the crank out and have it machined properly to take the right size bush or get hold of a short engine and use this . I'm erring towards the latter especially as it seems that the drilling of the existing crank would not only be a bigger bore but also deeper as the input shaft is also longer