US to EU XK engine specs

[fandeland]

Good day everyone

I have just started the overhauling of my 4.2L US specifications XK engine. While I'm at it, I'd like to upgrade it to European specifications and get a little more bhp. Being an auto box car, I'm inclined to get more torque rather than top end horses.
From what I could gather so far, I Know that EU specifications engines have triple SU carbs and different ignition curves.
My questions
Are there any other difference?
What simple and effective modifications would you recommend to get more torque?

Thanks a ton
Alban

[christopher storey]

The 3 SU setup is about the best you can get for a road car, although a much cheaper but non-authentic change , which is nearly but not quite as good, is to use the manifold and 2 SU HD8 setup from a 4.2 S1 or S2 XJ6 . The other eseential modification is to use the correct EU spec distributor with vacuum advance which gives much better part throttle characteristics than the US spec one which may actually have vac retard. As far as torque is concerned, particularly with an auto where the engine runs predominantly in the 1500 - 3000 rpm range , the essential is to check that you have the correct camshafts and are using the original cast type manifolds

[PeterCrespin]

Good day everyone

I have just started the overhauling of my 4.2L US specifications XK engine. While I'm at it, I'd like to upgrade it to European specifications and get a little more bhp. Being an auto box car, I'm inclined to get more torque rather than top end horses.

Very sensible, I'm sure, but unless you particularly have to have an auto, I can assure you the biggest bang for your buck will be to dump the BW boat anchor and go to a manual box. It will cost far less than a decent tri-carb set up with original plenum, will add to the value of your car, and give you massively more sporting performance even with your current Stranglebergs.

Meanwhile, having recently sold a car like yours, I found that if you disconnect the secondary throttle plate links where they attach to the carbs, you can swing the short links through 180 degrees and jam them against the engine-side manifold casting. This holds the plates almost totally open and they are held in place by return spring pressure on the relocated linkage. This costs zero, takes two minutes, is totally reversible and doesn't require so much as a gasket (unlike removing the whole secondary throttle plate aparatus and blocking off all associated passages and openings, which is slightly better).

[fandeland]

I got a shock when reading your suggestion, Peter, but after sleeping over it, I think you have a very good point. I don't need the auto box as such and since it is already out of the car, it is worthwhile doing the swap now.

I will keep my cast exhaust manifolds and the Stromberg for now. I have already block open the secondary throttle plates.

Is anyone aware of other differences between US and EU spec engines? E.g compression ratio, camshaft, valve size,...?

Would any XJ6 per 1986 be a good donor of manual gear box, flywheel, clutch pedal assy,...?

Thanks

[PeterCrespin]

Is anyone aware of other differences between US and EU spec engines? E.g compression ratio, camshaft, valve size,...?

Would any XJ6 per 1986 be a good donor of manual gear box, flywheel, clutch pedal assy,...?

Thanks

They hada vac retard dizzy which you hve to get rid of, even with the Stranglebergs in place. The compression may have been lower. Does your engine number end '-8' or '-9' ?

Being an auto, you should have a 3.31 diff rather than the 3.54. Even with a straight 4-speed that's not a bad ratio and with an overdrive box (which is your most likely find) it will be very relaxed on the motorway.
ill fit from the XJ6 but not the pedal box. There is stacks in the archives here about these conversions - it's a straight swap for the auto and you can keep your existing radio console and the XJ6 transission top, which makes it even cheaper, if you just adapt your existing centre console.

Pete
Flywheel and clutch w