Trying to look forward to a future MkII project, Iwant to get my motor sorted out first, then find a car for it. Should I build the stock 3.8 as much as I can? Or swap in a SIII 4.2 with some performance goodies? I read so much about the 4.2 water jacket issues, maybe the 3.8 would be more reliable in a high performance build? What are some different driving characteristics of the two?

 

The 4.2 engine was a bit of a cobble, based as it was on the original 3.4 litre engine of 1948. The blocks suffer from cracking between the bores and this is extremely expensive to repair. Later blocks from around 1982 have slots on the top deck, so don't crack.

If I were you, I'd stick to the stock 3.8 litre and rebuild that, it won't cost any more. However, even these engines can suffer certain issues, but I don't know the details, so try posting in the Mark 2 forum. Whatever you pick is going to be an old engine. You could, of course, put in a later engine like the AJ6 or AJ16, both sixes, but all-aluminium. They have no commonalities with the previous engine at all, but are more reliable generally, and lighter, of course. There is not much room in a Mark 2 engine bay, but Jaguar managed to fit the small Daimler V8 engine of 2.5 litres, however, a bigger V8 might not fit.

If you want to retain value, keep with the 3.8, as that's the engine it came with originally.

 

In general, the 3.8 is a higher revving engine, and the 4.2 has more torque. My choice might be for a mild 4.2 with the all synchro 4 speed. If you really want horsepower, I still would go for the 4.2 but probably with a modern 6 speed. And if I really wanted a lot of horsepower I would go for a more modern car. I really like the Mk 2, but you will never make it outrun a new Mustang.

 

NEVER SAY NEVER!!!!

Some said the AC Bristol would never outrun a Corvette but a chicken farmer in Texas thought different. Many young rich kids died in the AC Cobras when they were introduced.

Time and/or money and you can do almost anything.

I REALLY like the looks of the MKII but they are getting hard to find.
I used to work on a silver one back in the 1980's and I thought it was a really nice sport sedan. (alot nicer than my 1972 SI sedan)

I don't know how to advise but good luck on the project.

bob gauff