Why cant the 3.8 flywheel be used when swapping out a moss box for a synchro?
You could, if you used a 3.8 starter and redrilled the bellhousing for the different starter location…
The radius and teeth are different plus the teeth are also chamfered on the wrong side. The 4.2 starter is preengaged which is better, and it engages from the front.
Your bell houseing if one thats on the Moss box will also need machineing to fit the 4 syncro box…Steve
Right, if the 3.8 bellhousing is used on the new box (its input shaft bearing is larger) it has to be machined.
Perhaps the word Trans was not appropriate in this title. 
You’ll also likely want to switch to a diaphragm clutch. I don’t think any 3.8 e-type flywheels were double drilled. I believe some mk2 ones were but not E. I know my 64 isn’t.
If you retain 38 flywheel with 38 bell housing and 38 starter all you’ll have to do is machine rear bell housing face to accept the larger front bearing, as previously stated
I am assuming you just want 42 gearbox swap into a 38 to replace the moss and nothing else. If you take the 42 box and bell to a good machine shop they can do the work. This is what I have in place and it’s straight forward
Hope this is of some assistance
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There’s also probably not enough meat on an E-Type 3.8 flywheel to drill for a 9" clutch because of the way it’s scooped out on the back side.
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Very unlikely for americans but the 2.8 flywheel is a 4.2 flywheel, I think factory double drilled, with the 3.8 ring gear and diameter.
I would posit that if the thickness of the surface where the bolts would go through is at least 3/8 of an inch, that should be more than enough.
I wonder if the double drilled mk2 flywheels have a different rear profile. I’ve never seen one in person.
[quote=“Erica_Moss, post:11, topic:444350”]
I wonder if the double drilled mk2 flywheels have a different rear profile
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Probably. Here’s one from a Mk1 sedan, not double frilled but it shows the difference in thickness (& weight). This is drilled for a 10" clutch.
I drilled the original 3.8 E-type flywheel for the diaphragm clutch. No issues. BTW, the double drilled Mark2 flywheel is not scooped out to the extent of the E-type version. (It looks like the one in the post above, but with extra set of holes).
My original 3.8 flywheel was also drilled on a PCD to match and fit the diaphragm clutch, eight years ago.
I measured thickness on the 3.8 E-Type flywheel and it looks like you’re right. The thickness is about 7/16" or perhaps a bit more so it would be enough for the extra drillings. It just doesn’t look like it from the back.
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