I have a 81 xj6 . I want to take gearbox and engine out of a 83 xj6. Are there any changes that will prevent a straight swap over. Both are 4.2's

 

Fundamentally this wouldn't be a problem.

In 1982-83 changes were made to the cooling system and perhaps some other sub-systems that escape my memory at the moment but nothing major. Anything from the 'early' design could be removed and reinstalled on the later design engine.

Cheers
DD

 

if the 83 has a different cooling system and injection arrangement you can swap the inlet manifolds to suit, i know the inlet manifold on my 86 is different to the one on my 81 spare engine, the easy tell is the fuel rail size[larger on the later]