Bell housing swap

[abowie]

I am currently rebuilding a 3.8 FHC,
The car came with a Moss box which is too water damaged to rebuild.
I have an all synchro box from a 4.2 S2, but it does not have a bell housing.

1. Can I use the Moss bell housing on my 4.2 box?
2. If so, what modifications if any would I have to make?
3. Will I have trouble with the starter motor or tailshaft I currently have?
4. Will it work best with a 10" clutch or a 9.5" clutch?

[Doug Buchan]

Hi Andrew,
Yes you can.
Have your machinist fly cut the 3.8 bell housing to accommodate the larger input shaft bearing on the synchro box.
Use your 3.8 flywheel and 3.8 starter. Have the flywheel drilled/dowelled to suit a 9.5" clutch.
If your 3.8 is an early model, you will have to switch the bobbin type rear mount for the later spring type.
Source a 4.2 gearbox cover.
Regards,
Doug

[abowie]

Excellent. Thanks Doug.

[mgcjag]

Just to show the difference in the machineing...the first photo is larger for the all syncro

[abowie]

And here I am doing it.

https://youtu.be/uNFfRA3S_uM

[abowie]

My brother in law is a diesel mechanic and has a seriously big-ass lathe.

First I mounded and trued the backplate with a dial gauge.

Then I bolted the bell housing from my Moss box to the backplate. I centred it using a dial gauge on the outer rim of the largest cutout. I got it centred to within 2 thou without much difficulty.

Then I tightened the bolts, rechecked the centre which hadn't moved and then machined the two cutouts to accept the larger all synchro box front bearing.

Despite my trepidation it was easy and took me about an hour.