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MG MGB Technical - Wrong Crank!

I'm changing my engine for a low miles recon unit, which came from a crashed rubber bumper MGB GT of unknown year. (mine is a 77 RB roadster)

I was having doubts about the crank when I came to install the pilot bush, in that the crank was nowhere near deep enough to fit the bush to.

Now I have my engine out, the gearbox input shaft sticks out 30mm from the mounting face, and I think the hole in the crank is only 15mm deep from the face of the back plate.

Result: the bolts won't ever tighten up!.

Can I easily remove the front shaft from the gearbox (whilst it is still in the car), and swap it for the one on the spare 'box (which has been cut down), or should I just get the grinder to the one on the car, and take 17mm off the end?

I suppose if this engine is any good, I won't need the extra 17mm on the input shaft ever again!
Martin Layton

You may be able to pull the input shaft with the trans in the car depending on how tight the bearing fit is in the case. You could grab the shaft wth a bearing clamp and use a slide hamer but you will likely ruin the shaft. Normally you use a brass drift to drive the bearing out from the inside of the case. If you manage to get it out make sure you don't lose the needle bearing that fits inside the input shaft and over the third motion shaft.
John H

Thanks for the reply. I've checked the manual, and the chances are the needles will fall out, and wreck everything, so its out with the grinder!

I suspect it is a Marina crank, as I think Marinas used a Triumph gearbox.
Martin Layton

Martin, it is a caged needle bearing, the needles won't fall out, just the whole bearing. I believe that the loose roller bearing style went away with the introduction of the 4 syncro box.
John H

you cannot remove the input shaft without removing the layshaft shaft allowing the lay gear to lower in the housing. The gear will not clear the layshaft unless it is lowered.This means trans must be pulled. I would mask everything well and grind the extra off if you are certain thats all it takes. I am not familiar with the crankshaft you are talking about.
Sandy
Sandy Sanders

Strange, I don't think my Dad changed his crankshaft when he installed an MGB overdrive in the Marina... He did have to build a new floor to fit that though! I was wondering if its to an automatic since most autos usually don't have as long of shaft. Also, are you sure its not something stuck in there? I cant see there being two cranks so closely built to each other. Chrysler and others did that back in the 1960's on autos vs. manuals so I have heard, but never heard that on a British manufacturer.

-BMC.
BMC Brian McCullough

The input shaft can be removed through the front I've done it to grind the shaft to fit three main bearing motors.
FOR SURE RIC
Ric Lloyd

Progress so far.

Removed 17mm off input shaft with grinder. Bevelled cut end.

Took 5mm off spigot bush.

Made clutch alignment tool.

Fitted bush.

Alignment tool won't go in bush.

Reamed bush to take tool. (same size as shaft.)

Refitted engine.

(two words to describe hours of work, including lengthening engine crane 3", pulling, twisting, levering, lifting.)

Fanbelt is far too long.
Swapped front pulley: discard heavy damped affair for larger diameter MG one.

Spun on starter without plugs to get oil pressure.

Notice large puddle of oil running out under car.

The filter housing is pouring out oil, despite rolling the engine on its side groove uppermost, carefully fitting a new gasket to groove, carefully fitting housing, and carefully torquing it down.

Something must be seriously wrong, like the seal is broken or the wrong size.

I will have a look after dinner.
Martin Layton

Update:

I removed the "new" seal ring amd jammed a square section o ring (just a bit larger) from the spares box in the groove.

Then I just carelessly tightened it up with a ratchet soaked in oil, put the plugs in, and started it up.

5 bar oil pressure: no leaks! Sounds quieter than the one I took out, seems to run smoother too: probably has 4 cylinders working not 3!

And the clutch works ok.

Tomorrow I need to find all the tools, retorque the head, reset the tappets, flush the cooling system properly, reconnect the heater, set the timing, check the carbs and clean all the splilt oil away.

Then I can road test it.
Martin Layton

Martin, with the oil filter off take a really good look at the grove for the gasket, there may be another one stuck in the bottom of the groove, it is very common.
John H

This thread was discussed between 25/10/2006 and 26/10/2006

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