So, this one is a real headscratcher.

I need to replace the harmonic damper on my 1992 XJS 5.3L (part #eac9693). I took it to my garage so my mechanic could remove the radiator and cross-over pipe, see if they need replacing, and to have him get to work on replacing the crankshaft damper. I ordered a refurbished crankshaft damper from the same, very reputable place, where I purchased my refurbished crankshaft damper for my 1993 Daimler Double Six 6.0L (part #EBC9389)

When my mechanic got the damper off my XJS, he found it was not the same as the refurbished part EAC9693 that I purchased. The refurbished damper I ordered (EAC9693) is tapered. The crankshaft damper pulled off my “5.3L” fits a parallel. It’s not tapered, it also has a ridge, and a wider diameter, and the notch is not the same place (see photos).

My question is: does anyone know if the last late model 5.3L XJSs produced in 1992 had a different crankshafts /crankshaft dampers to all other facelift convertible Marelli XJS 5.3L produced?

OR . . . is it the following:

My mechanic suggested that at some point in the car’s history the engine might have been replaced with a 6.0L that was used in the 94-96 XJS and XJ40/Daimler Double Six.

So, I got a photo of the refurbished crankshaft damper I purchased in 2021 for my Daimler Double Six 6.0L (Part# EBC9389) and . . . bingo. It’s exactly the same.

It makes a little more sense now that my mechanic had to do some alterations to the new water pump that I purchased and the WOSP alternator that were both marketed as “bolt-ons,” but required a bit of workmanship to fit. The new stainless steel cross-over pipe also is not an exact fit.

Tried to get the engine block number; but too unclear. Maybe purposeful from previous owner’s mechanic?

Does anyone know any other tell-tale way to easily distinguish if the engine is a 5.3 or 6.0? Remarkably, the car has driven without any problems. My mechanic said it is possible to put the 6.0 into a car originally fitted with a 5.3; but not the other way around. So, I could have a 6.0 fitted to a GM400 transmission? It’s definitely not the 4L80E that I have in my Daimler.




It’s never about the destination with these cars, but the journey!

 

To know for sure, check the stroke of the crankshaft with a plastic straw or similar, through the spark plug hole 2.750 = 5.3, 3" 6.0

 

What is the engine number, Charles?

 

Other thought is at some point in the cars life a replacement damper has been fitted? As far as I know the 5.3 Marelli and 6.0 dampers are completely interchangeable, so it really shouldn't matter what is on the engine. The difference is the 6.0 did away with the tapered cone on the crankshaft and made it a single piece. It functions the same.

 

Your mechanic is right... It is possible to put a 6.0 into a 5.3 car and use the 5.3 transmission becasue the 6.0 blocks have all the 5.3's bolt holes but they were undrilled, The bolt holes would need to have been drilled to fit the 5.3's transmission so the origional 6.0 transmission bolt holes should be visable. Another tell is the alternator, the 6.0 used Desno alternator with a 5 rib belt and pulley, the earlier cars used a 4 rib belt and pulley for the alternator. Another tell could be the A/C compressor, all the 5.3 used the venerable GM A6 compressor and the 6.0 used a Denso. The fuel rails are diffrent on the 6.0 too.

 

I fitted the later crank pulley to my 84, as I fitted a 120 amp alternator and got fed up with the noises coming from the belt and weren't sure if it was the bonding of the pully or the belt,
At the time the later rebuilt pulleys were being offered on Amazon from the USA,
As it turned out the old pully was very sound so that was sold which offset the cost quite a bit.