XJ6 engine attitude REQUEST

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?

I am sure I have read the XJ6 engine is tilted back slightly, (and that is why extra silt accumulates at the rear block coolant passages), sorry I dont know the angle though, but some Googling may help you

dont know if this will help, but the topic is discussed

http://dazecars.com/dazed/JaguarIRS5.html

Just checked my S11 and I can confirm the engine definitely slopes down at the rear.I could only guesstimate the drop on the cam cover acorn nuts there is about a 25-30mm drop from the front nut to the rear one.

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

We are trying to confirm (or refute) that the engine (and thus the gearbox flange attached to it) have a slight angle difference from rear differential. That is, the transmission end and the differential end are not exactly parallel. Or are they? Accurate angle data measurement really appreciated!

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Isn’t the horizontal measurement a better verification; the valve covers are parallel to the crankshaft…

The alignment tool for the S1 propeller shaft prescribes a straight line, using front of the forward shaft, front and rear of the rear shaft. It is not measured against ground level - and allows for the propeller shaft to slope…

I don’t say that it does, but if it does; there should be a measureable difference between the height to the ground of the gearbox output axle and the diff input with either engine installed…

Nobody has reported any vibration problems when lumping with various engines - and as some engine/gear mount motion is inevitable; the universal joints, properly installed, may be tolerant to angular inputs/motions…?

Frank
xj6 85 Sov Europe UK/NZ)
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To clarify our measurement request please see this description: http://krissmotors.com/WP/2018/04/13/engine-mounts/ 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?

I will be back to my S1 car location the end of this week. If no one has provided you the answer I will put my car up on my lift and try to take the measurements for you.

Gordon Mortin

Thanks Gordon … really would appreciate that!!

I expect to be back on Sunday so hopefully I can do it on Monday. Send me a detailed message with what you want me to measure. I can also take pictures too. With the car raised so the tires are just off the ground I should be able to lay a level along the valve cover lift the appropriate end to level Abd determine how many degrees off level the engine is. I should be able to measure how many degrees off vertical the rear seal surface of the transmission sits and the same for the differential drive shaft surface.

Gordon, really appreciate your offer to help, but I think this issue is resolved enough so that additional measurements are unnecessary. We were able to get the angle difference between the engine and differential down to about 1.5 degrees, and that should be fine. Most Jag folks probably don’t bother to even measure this.

Glad you got it resolved.

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