Our XJ6 restomod project is swapping out the original 1972 Jaguar engine and replacing it with a 2018 Chevy LS3 EFI V8 (essentially a Corvette engine). It fits easily into the XJ6 engine bay.

However, we've noticed that the LS3 engine attitude points slightly up by about 4 degrees using the mounts we've designed which means that the end face of the transmission tilts down by about 4 degrees.

Our Jaguar IRS stock differential is exactly perpendicular to the ground, so we'd like to eliminate the 4 degree difference to avoid driveshaft vibration.

There isn't room left in the transmission tunnel to raise the transmission up any more, so the only option appears to be to lower the front of the engine. However, to eliminate the 4 degrees we need to lower the engine:

sin(4 degrees) x mount-to-mount length 40" = 2.8"

There isn't a 2.8" front gap ... perhaps half of that between the oil pan and the front suspension crossmember/steering rack.

REQUEST: could someone with a Series 1 XJ6 please measure the attitude of the front of their engine relative to the ground? Is it exactly 90 degrees? Or tilted up or down?

 

A couple of thoughts.


1. If you are keeping the 2 piece drive shaft, measure each segment. The rear part should not vary. Caveat, I'm fuzzy on the architecture there. The front portion might be the only issue.


2. If a one piece shaft as most opt for can be different.


3. Ujoints as used here do have an angular tolerance. 3 degrees mentioned by many Others exceed that. And, at times it is OK, and at others, not so much.


4. I've read of the pan vs frame issue. and solutions ranging from cutting and welding to shopping for a better fit.


5. My LT! is visually level. I use a one ice shaft. No issues at all.


Carl

 

There are many ways to lower the engine.... here are some ideas.

1. Redesign your engine mounts and perhaps source a low profile oil pan.

2. Add a spacer to the top of the rearward subframe mount. This has its limits but can get you closer and also effectively increases camber which may be desirable for a performance car. Especially so for these Jags with wider tires...the scrub radius goes more positive and causes camber goes negative in some aggressive driving situations.

3. Jag solved this problem with a 2 piece drive shaft. Just retain the OE style drive shaft and perhaps upgrade to the improved series 3 center bearing setup and the angle will be less important becasue you can space out the center support to take up the total required angle over 3 joints, thus reducing the angle on each u-joint by 1/3. With a creative use of spacers you can put the center support in a wide range of positions up/down and left/right. The forward/back position is very limited but nearly perfect where it is.

I know you've probably read on the internets and from you local drive shaft guy that single piece drive shaft shafts are better, they are not. A well designed 2 piece is far superior in every way to a 1 piece in many situations and yours is one of them.

 

Here is the answer: Use the proper engine mounts and it will be level!


You can see how to do a XJS in this video, there are others to see on this site including pulling the original engine and trans and rebuilding the rear end.
Even a short talk on the phone with Andrew from Jaguar Specialties...

 

Could someone with a XJ6 (preferably a Series 1) please measure with an angle finder the vertical position relative to level ground of the engine front face and, if possible, the rear differential/driveshaft face?

This would be very much appreciated.

We are trying to confirm (or refute) that the engine (and thus the gearbox flange) have a slight angle difference from rear differential.

 

To clarify our measurement request please see this description: Engine mounts - XJ6 Restomod and specifically the ENGINE ATTITUDE PROBLEM section. We’d like to know how original XJ6 setups looked, especially the Series 1 (we have a 1972), and whether the transmission end and differential end have exactly parallel faces (although the differential may be lower than the engine and the driveshaft may slope down a few degrees – this is not our question).

Does anyone have an accurate measurement of the relative angles between the transmission and differential faces?

 

My observations suggest that the original transmission was parallel to the center line of the car. That said, as it was really shouldn't matter to you much. You need to deal with the situation as it is present. The Dana 44 like differential is offset to one side and this is one of the reasons why Jaguar used a center bearing and additional U-joint to take up the angle and create a CV effect for smoothness.

 

Icsamerica , . good stuff. After reading it I kind of wish I had kept my original driveshaft and modified it. As it is, I have a new one piece drive shaft now.
Probably not too difficult to find the parts that will replace the ones I discarded. Who Knows