Hi Everyone! Ok. Here is the situation. My 89 XJS Convertible has a bad V12.
I bought the car with an extra engine, which is good. I pulled the bad engine out
of the car, and began the process of transferring components from the bad engine to the good. The "good" engine is an '83, according to the serial #.
Here is my problem. The 89 engine has Marelli ignition, and a Bosch alternator.
the 83 was Lucas. For one, the pulleys are different on the alternators. That is not a big deal, since I could change the balancer/pulleys. But here is where it gets interesting. The Marelli engine has a crankshaft position sensor mounted on the timing cover just below the pulley. The 83 does not. Not even a bracket to
mount the sensor.
Do I try to convert the car back to Lucas, or try to convert the engine to Marelli? It looks like I would need to remove the heads to change the "timing cover" where the sensor is mounted. I really did not want to get into that.
Another parts car.....???...
Thanks for your help!

 

From best I remember, I think you can change the timing cover without removing the heads. It is a pain I know, but having everything out is a awesome advantage. I am new to Marelli, but I like the concept, and think it should be better as far as firing advantage, as long as it works. Although my last V12 was a 71 XKE, and I put the Crane XR3000 on it, with the PS90 12 volt coil on it. I literally drove the car like I stole it. It was a blast. The ignition operated flawlessly in the 10 years I owned the car.

 

There are good arguments both ways, and even an argument for aftermarket ignition upgrade....which would likely require using the Lucas distributor.

Personally, I prefer the Lucas CEI over Marelli so that's the route I'd take.

BUT.....

IF the front cover CAN be removed without removing the heads that would probably be the most direct path to a running engine......if that's a priority for you. No messing about with mounting the CEI amplifier, re-wiring, etc.

What does the shop manual say about removing the timing cover?

Cheers
DD

 

The engine loom and the ECU are different as well. There is also a sensor on the flywheel, I think, on Marelli cars, but I may be wrong about that. I am sure you can get the sensors fitted OK and then a dizzy swap and timing it up and off you go. The timing cover will come off on its own with care, the Great Palm's book explains.

Greg

 

Greg,
Thanks to you and to all for the great information. I am going to put the timing cover , pulleys,
and sensors on the 83 engine. But, that brings up another question. You are right, there is a sensor mounted in the flywheel area, on the "inspection cover"at the bottom. Can I use the
flywheel that is on the 83 engine? Or, is there something special about the 89 flywheel since
it is used with that sensor? Swap flywheels too? Sheesh!! Thanks for all your help

 

Hi there


I would retain the Lucas distributor and switch to Crane ignition system.


Our 1976 pre-HE has Crane installed and runs far better than the original ignition format.


have fun
BernardS

 

Mine is not a Marelli car, so I am not sure if the central hole in the flywheel is the same. If it is (and someone will know) then you can swap them. In principal, I think you are doing the right thing, the mechanical changes you need to mount the sensors are far, far, easier to be sure about than trying to get the loom to run a Lucas system.

Greg

 

That sensor on the flywheel is for engine speed. And yes the flywheels are interchangeable.

Go Marelli I have had mine for 5 years now and no problems. Much better spark control than any Lucas system. The only better is a fully mapped aftermarket system.

A lot people are scared off by Marelli but if you keep the regular maintenance up, replace spark plugs (the main culprit I believe for the infamous Marelli fires). My Marelli dissy is NOT modified in any way and I drive my car daily.

Why don't you use the 83 engine to rebuild the 89 so you keep the original engine number. I think a numbers matching car will be rare in 10-20 years. Also how do you know the condition of the 83 internals...

 

Warrjon
The crankshaft oil seal arrangement and the actual block and crankshaft at the gearbox end are different between these two engines, so if the old crank cannot be used, there is a problem in swapping out the bits. Also, like me, the guy might be scared stiff of taking the engine apart!

Greg

 

Greg,
You are right. I am VERY afraid of pulling the heads. I saw it on You Tube. No Thanks!!
Thanks for all the info, just to be safe, I am going to swap the flywheels too. What a job this has become!

 

As overwhelming as it may appear, these engines aren't that bad to rebuild in my opinion. To me, most of the work is in taking the engine out, putting it back in.

 

Greg
Why are they different? Up to the rear oil seal change they should be the same.
I think that was mid 89 about engine number 66784

 

I don't think the flywheel matters. Mike in Ohio told me that he used the aluminum flywheel when he did his 5 speed conversion, and actually made a bracket to hold the "sensor". These aren't sensors guys. They are small magnetos. All that happens is when the iron teeth of the flywheel pass the mag, the gaps cause this thing to produce a AC signal. That signal feeds the Marelli computer what it needs to calculate the firing. Same with the front "sensor". It only has 3 fingers, and this front "sensor" is what gives the computer the signal to calculate timing.

 

I did not intend to say they were defintiely different, but that they well might be. If he was to take the parts out of the 1983 good engine and try to build them into the 1989 block, because the 1989 engine's crank, block and rear oil seal arrangement is/may be different, then if he needs the 1983 crankshaft, it might not go into the 1989 block. Or for that matter, vice-versa.

Greg

 

In early 89 Jaguar changed the block and crank (can not remember what engine number) the later block/crank are set up for a 1 piece seal. Getting rid of the troublesome rope seal. So you are correct.

Which is why I would use the 83 engine to rebuild the 89. I doubt the crank would be damaged they are are hard as. I have seen 2 V12's run with no oil and all that was needed was new bearings not even a crank polish.

The 83 crank can be machined to fit the 89. The 83 block can be machined to fit the 89 crank. Either way the seal must be the newer lipseal.

 

If you get a head puller it is easy.

I would NOT put the 83 engine in without knowing its condition. I bought a 6.0L from a low mileage XJ40 and after stripping it down it had a dodgy head gasket, it WOULD have gone in a few years at most. Both the head gaskets were rusty.

If you go ahead and just drop the 83 engine in I think you will end up regretting it.

DO the job once and do it properly. Rebuild the original engine. You dont even need to pull it out of the car.

 

I have just re-read your original post and if this were me I would tackle it in the following order.

You did not say what the original problem is. If the the 89 engine is bad pull it down and find out what the problem is. I would expect the crank is good most other parts pistons, rods, heads can be used from the 83.

Survey the damage and rebuild the 89. You then are certain you have a good engine to go back in.

BTW I think the oil pumps are different as well. Depending on many things (including Sun spots) the 89 might have full flow oil cooling or it may not.

Back to the tear down.

1 Pull the heads, check valves and seats. If they are good a light skim and they are good to go back on with new gaskets.

2 Drop the sump and remove the caps if the bearings are good and you want to save money put it back together.

If a pistons is damaged replace it along with it's sleeve from the 83.

If you go this way it might take a little longer but in the end you have a known GOOD engine.

 

An engine number for the '89 from the OP would save the need for speculation re seal type.
I have an '89 and it is still rope seal. My engine number is 1200 short of the change over point.