Making bellhousings?

[Spac]

I've got a couple of gearboxes that need to be adapted to different motors, and there are no commercially available bellhousings or adaptor plates available.

Now, what I've been thinking is that if you got the motor's original gearbox and bellhousing, and bolted a piece of (say) 3mm aluminium in place of the motor, you'd be able to find where the centre of the input shaft is, relative to the mounting bolts.

Then, if you cut up that bellhousing, and the one from the donor gearbox, you could use the aluminium plate to align the two parts, and have them welded together.

Tell me if/why this wouldn't work...
I have access to cheap, good TIG welding, FWIW.

I'm not worried about the length of the BH, just whether this would be accurate enough to get the engine's crankshaft and the gearbox's input shaft aligned properly.

[Kaptainballistik]

Best way would be to mill / hack off the old motor flange , Make a new motor side up from 10mm plate and weld that to the bell housing.

Well thats how Mr OToole does it ( But he is a toolmaker and likes measuring stuff!) Are the current bellhousings removable? how about a adaptor plate A La Celica?

Only thing about joining the 2 bellhousings is will they be in the same relative piece of space to weld together? Ill ask Gt on Sun

[Andy Crane]

I had to make a new bell housing to fit the Lexus 6 speed into the 504 ( and a new rear end to mount to torque tube .)
It has now done 12 rallys with no problems , no clutch shudder , no oil leaks , the bolts have never come loose .

To make new bell housing machine a steped steel shaft that fits the centre of both bell housings , ie the Lexus and the Peugeot , the two bell housings have different size front bearings they are also different heights hence the need for the step on the shaft ..
The steel shaft was then mounted on a 19mm steel plate ( plate and shaft must be square) then the complete Peugeot bell housing was droped over shaft and bolted tight to the steel plate , the shaft keeping it on centre line.
The plate shaft and bell housing was then placed on the mill and the back of the bell housing cut off ( while still bolted up tight to plate )
Then about 40mm ( this distace needs to be calculated to ensure that the thrust bearing is in the right spot to push the pressure plate fingers ) was cut from the Lexus bell housing on a mill to ensure that the cut was true to the mounting face to gearbox.
Fit the rear section of the Lexus bell housing onto the shaft and sat down on to the remains of the Peugeot bell housing ( the shaft keeping it all nice and centered and square) .
The entire plate , shaft and composite bell housing was the taken to Pro Ali and welded together while still on the jig.( 19mm steel plate may be an over kill as it was really heavy to transport , about 60 kg)
The new bellhousing was tremoved from the jig and placed on the mill and the engine end was machined to be true to the gear box end.
reassemble gear box fit to car and go rallying!

[buzzard]

I have seen this done with automatic gearbox bell housings.

If the bell housing unbolts, it will have a spigot/recess that is concentric with the crankshaft.

You are more than smart enough to work out the rest.

Chris