V12 distributor - 85 v 88

Hi guys, so I got the XJ12 back… its fitted with an 88 engine (lucas) but running with a 85 distributor, well its not running, hence my post. We can not set the timing, when we do its about 30 degree and it pinks… so I am going to have the distributor rebuilt as everything else seems to check out.
The question is, Is there a difference in the distributor of an 85 over one from an 88??

I have an 88 XJS, and pretty sure Lucas distributor is the same going back to all HEs?

So what do you mean can’t set timing? And its pinking/too advanced? Could distributor just be a tooth off?

I cant remember, doesnt distributor gear have 14 teeth? That is 25.7° per tooth. I had to try three times installing mine, very easy to get one tooth off.

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Hi Greg you would think that it was a tooth out but I am told it is cock on… I have found a company here in the UK that will rebuild the distributor, they think its more of a mechanical issue then anything electrical… I’ll keep you posted…

If the distributor is indeed properly aligned, most probably it’s a stuck centrifugal advance or broken/stretched springs.

hope so… thanks guys

Looks to be that from 81 to 89.5 the HE used distributer number 36DM12:

~Paul K.

Hi guys, Lee at H&H ignition services says the distributor checks out… mechanically and electrically… I’ve fitted it and knocked it back on the body, she starts and runs roughly. Have someone coming with a strobe light and a Jag brain to help me get it sorted…

Perfect timing is 18 BTDC at 3000rpm with vacuum advance disconnected, engine fully warm. But if it’s running that rough, you may not want to rev it so high.

So at idle with vacuum advance disconnected, it should be 0-4 BTDC.

If it will only idle with vacuum advance connected, then timing at idle should be around 16 BTDC give or take a few (assuming you have oem brown vacuum modulator set up for vacuum advance)

And yes, it is interesting that jaguar advanced the timing so much at idle. I believe it was for better gas mileage, and cooler engine at idle.

Greg, quick one, should the distributor be sitting directly on to the engine OR should their be a round metal base plate that sits in-between the distributor and the engine? I only ask this as I have a sketch that shows one and as the gears are helical the seating position (up or down) will obviously change the rotor arm position??

That picture shows the early OPUS ignition – and no trigger board, so a carb engine.

I agree, it looks like a plate of some sort was involved, but there’s no such plate on the mid-80’s H.E.

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Thank you Kirbert, appreciate the info…