Hello everyone! I'm in the process of putting an AJ16 SC engine in my series 2 swb, and here in Sweden we have very specific rules when it comes to engine swaps.

If I can convince the car inspector (term?) that I've converted my XJ6 into an XJ12 in all the ways necessary I can use the V12s horsepower as a base. Here we can add 15% from the original car when doing an engine swap, and that would make it just enough.

So I need some proof to present.


The only things I have found that differ is the front springs and sway bar, is there anything else?

And I found somewhere that the old 4,2l engine weighs about 275kg and the AJ16 240kg, I have no idea if that's correct, can anyone confirm/correct this? My thought is because the new engine is lighter it seems like a bad idea to use the V12s springs, so I'm hoping I only need to fit the bigger sway bar. I would really appreciate some help on this! /Peter

 

Peter:

An interesting project. In terms of the mechanicals, the V12 cars used the GM400 transmission instead if the Borg Warner 66, and as you have found, heavier springs and sway bars. The brakes were perhaps also upgraded but I am not certain of that.

 

Tyres originally were 215/70 R15, slightly wider than the sixes at 205. Rear diff ratio may be different. Your weight for the XK 4.2 sounds about right, as I always read here in the UK it was 600lbs. Not sure if that included the auto transmission, though. The AJ16 with its aluminium block and head will be a lot lighter, so you may have to adjust your front springs as the ones for the 4.2 will likely cause the front of the car to be rather too high. I would have thought your 240kg (= 529lbs) sounds about right.

 

I am nearly finished with installing a rebuilt with new pistons AJ16 SC motor with a GM 4l80e transmission managed with a EFI source ECM/TCM. I measured the front height before I removed and reinstalled Engine/ trans and it rose by a 1/4 inch or almost 8mm. Very easily manageable to adjust height. If you need sway bars, Go to a company out there known as ADDCO.com. They have a 25mm Sway bar for a XJS, ( same subframe ). They also have a 19mm rear sway bar for a XJS that will fit with some work. With some Bilstien shocks and some lowering springs, Hold you arm out flat and swing from left to right and that is how my car goes around a corner.

Thank you

Larry Louton

 

Well that sounds great! I will surely check out the xjs sway bars, are they a better fit than the V12 ones? It sounds like you have driven your car, how does it feel? Anything I should know before I start modifying my car?

How's the breaks? I feel like installing bigger ones, never hurts...

Good luck on your project!

 

Thank you! Yes my intention was to fit wider tyres anyway, but that's good to know.
Nice to know that my numbers was in the ballpark at least!

 

Thanks! I looked around in some shops on the internet to see what would fit on the XJ12 and not on the XJ6, the breaks seemed to be the same.

 

My XJ6 Series 3 had 4-pot front calipers with vented discs and I don't think you would really need anything more than this.

 

On a Series I car the brakes are different: vented front discs on the V12 and solid discs on the 6-cylinder.

At some point the 6-cylinder cars got vented front discs as well. I'm on my first cuppa coffee so I can't remember if this was at the start of Series II production or sometime during Series II production. I can't recall any other differences with respect to brakes.

The V12 cars also had a limited slip diff as standard issue...but I doubt that this has any bearing on the issue at hand.

Cheers
DD

 

I did not know that, but that's an easy one to check, I'll go out to the garage to check later. I assume that the vented disks fit the older cars... Thanks.

 

I use shift tower from a V12 powered fan XJS in my XJwuzza 6. The former uses the GM pattern for the detents. Better suited to the GM transmission in my car.

So, the shift towers differ between V12 and DOHC 6 powered cars. The former a GM transmission and the latter a BW!!!

Carl

 

I see, I'm pretty sure that's more information than the inspector wants, but still good to know!

I'm no where near installing the engine and trans yet, but my original plan was to use the entire linkage and the J-gate from my donor car. But maybe that's impossible? What do you think?

Thank you!

 

In my research restoring my 1975 XJ12C (started with and subsequently abandoned a rusty XJ6C) here is what I am aware of:

1) Brakes are all the same starting with SII. 4 piston vented in the front, 2 piston solid in the rear.
2) Front sway bars are larger and unique to the V12
3) Steering racks are the same but changed ratios in the SIII timeframe
4) Front springs are unique to the V12
5) V12 cars have a limited slip rear differential

I have not found any other differences other than the Tachometer inside and the V12 badges on the body.

Eric

 

That's perfect, great to hear from one who already done the research! Thank you!

And XJ12C, that's really something!