Thread: 304 Jaguar XJS conversion/rebuild.

Cool car mate, never really looked at Jags but this should be fun. Have fun going to shows and annoy the Jag purists

I too love these but would never buy one stock.

Personally i feel with a build of this magnitude it's be remiss of you not to at least tickle the motor; though it's a logical and sound choice as it sits. Lot of 308/350 and some 304's find their way into XJ6 jags but i don't think i've seen an XJS done before.

Oh, I'm sure some day the engine will get warmed up. But for the conversion and engineering etc, it just makes a whole lot of sense to leave it stock. All I have to worry about then is wiring and plumbing if things don't work right away, instead of what if's with other issues. The build isn't really that huge, it's just some rust repairs, respray, interior and engine swap. Nothing particularly difficult or ground breaking in any of it. The goal with the swap is to have a car that is as reliable as a modern vehicle built in this configuration from the factory and also for it to be able to do anything a car should be able to do. That includes sitting in peak hour traffic, long road trips etc. This isn't going to be a one trick pony that goes fast for five minutes then overheats, or one the police can pull over and defect.
The V12 is a pretty poor engine, Jaguar never really had the R & D money to throw at it, it could have been much, much more but it was never fully developed. Now, the 4 litre manual XJS's were pretty good cars, but also pretty rare and much more reliable than the V12. And almost as fast too, with much better balance.
As I said, with a 3.55 diff, it won't be slow.
I also plan to have the exterior and interior look stock, then I can go to car shows and have it parked with the bonnet open. I love watching self righteous purists convulse on the ground.

The V12 was just never developed properly. This is evidenced by the fact that when they finally put decent engine management on the last few, the power and torque went way up and so did reliability.
The XK is a fantastic engine (always wanted to hot one of the injected ones up and back it with a 5 speed) and the AJ six is also fantastic and has plenty more in it.
If an XK fit easily into an XJS I would've considered it as a swap with a 5 speed.
But, you just can't argue with an injected 304 and 4 speed auto for $800 with harness, ECU and all accessories!

I like the way you think. Get all the conversion/engineering stuff sorted with stock stuff and go from there. I wouldn't even waste time going 355... sounds more like it's a GT type of build with effortless cruising the plan?

You're also bound to get the obvious queries as to why you didn't go Ls1.

Back in the 1990s I knew a guy who had a red XJS with a 350 on gas. I rode in it a few times but can't remember driving it. It was a very nice city car and even better on the highway.