Hi All,


New here, hope this isn't a stupid question! lol


I have also had a quick search and found very little.


I would like to end up with a V12 XJS with a mildly tuned engine and a manual gearbox. Due to working long hours, all the work to do that is likely to take me a long time. So I have already thought that the best way to do this is buy a useable car to enjoy in my spare time while I build up a spare engine and gearbox to fit.


The consensus seems to be that with a manual gearbox with over drive top, the 3.54 final drive of the 3.6 is ideal. Also, a lot of people are using the Getrag 265 box from the 3.6 to convert V12s.


So with the fact that I intend to build a spare engine and swap it over, would I be better off starting with a 3.6 manual vehicle?


Am I being stupid?


Cheers
Sean

 

Imho no. You'll need to do an awful lot to get that V12 running. Not weld Ing or so, but you'll want to adapt some engine mounts. You'll need a different power steering system with cooler. Millions of little bits like oil cooler for the engine, different radiator, different mountain points for the engine to the front subframe etc.

It would be easier to use a worn out V12...

 

Interesting project. My own opinion, like Daim's, is that you would do better to buy a V12 and add the manual gearbox to it. The reasons being:

• All the V12 installation, which is complex, is done. You will have enough to do refurbing it all!
• The 3.6 manual gearbox is not up to the V12's torque delivery, so once you start using the power you will break the gearbox.
• Anyway, the 3.6 gearbox will not fit the V12, so you will need an adaptor for the bellhousing.
• The 3.6 exhaust system, the ECU and its loom, maybe some dashboard clocks, will have to be changed, so you will end up having to buy a V12 in addition anyway, to get those bits.

What you will need to source in addition are:

• A Jaguar manual pedal box. These come up on ebay pretty often, so you should be OK
• A gearbox and an adaptor ring to connect it to the V12. Realm Engineering in Pershore, Worcs, advertise such a thing. BEWARE, hot all models of V12 have the same bellhousing fixings, so you need to be engine specific before buying an adaptor. I believe Realm can also supply a Supra gearbox that is tough enough. No idea on costs, never tried them, no idea what they are like, but well worth a call to them. You are going to need all this whatever car you start out with.
• Depending upon the gearbox ratios you end up with, you may want a lower ratio diff. The 3.6 models, both auto and manual I think, have one and the 3.6 diff and the 4 litre too I believe, is a direct no-problem swap into an inboard braked V12 car's rear axle.

Keep us up to date with progress and good luck.
Greg

 

I'm on the last half of a similar project....converting a Series III XJ6 to a V12.

In my case (and I suspect yours, too, if you push ahead) getting the engine and trans installed will be the easy part. As mentioned the "little bits" are what really take up the time....cables, hoses, wiring bundles, oil and fuel pipes, etc.

If you buy a donor car for the V12 make sure to remove *all* V12 specific items, right down to wiring and connectors, throttle cable, clips, brackets, bolts, instruments, AC hoses, etc. If in doubt, remove it and keep it for the project car.

Cheers
DD

 

Thanks for quick the replies guys :-)


I did suggest I was being stupid lol


I wasn't overly worried about ECU and wiring, as I would probably go for an aftermarket programmable ECU like the Emerald anyway. But I hadn't really thought about all the little bits and bobs. So yes, on balance, probably better to start with a V12 car.


Greg, I know what you are saying about the gearbox, I was a little wary of using the 265, as Jag chose to upgrade to the 290 box on the 4 litre, but lots of people seem to use them. If I start with a V12 car, I will probably go a different route for the gearbox.


Thanks for the suggestion of realm engineering. I had a quick look, and they seem to have switched off the link to the "gearbox upgrades". Looking at the pictures on there website though, I think they are using the Toyota R154. I have used one of those in the past on a small block chevy using a bell housing from Dellow Automotive. They are a great gearbox, very strong and with a nice shift quality. Unfortunately they are as rare as rocking horse poo now :-(


I guess a Tremec box is the safe option, as at least they are readily available if a failure occurs.


Thanks for all the other info to, much appreciated :-)


I will keep you updated, it will be slow though, not even got a car yet lol


Cheers
Sean

 

For the price of the V12 cars I believe that's it's best just to buy one. A V12 convertion will nickel and dime you to death. $6000 buys a decent V12 car here

 

I think on balance the v12 vehicle makes more sense.


Especially as there seems to be question marks over the suitability of the 265 box on a mildly tuned V12.


Thanks everybody for your responses and advise.


Cheers
Sean