This distributor came out of a box of MK7-9 parts, but I a dont think it is from those vehicles, as they are clearly stamped with a model number on the body
This unit has no markings on the body at all, (except the normal advance script info)
It may be from a MK10/420G or possibly an XJ6 S1 or S2
Tony, the backwards clamp with the (impossible) tightening nut facing to the engine block definitely makes this a DVX 6A or possibly an earlier DVX H6A distributor. These were used on the Mark 5 and Mark VII and XK120 and XK140. However, the advance curves were different depending on the application.
If you take it apart, you will get a better idea what model it came from. You’ll need to remove the three screws that secure the top half of the distributor to the bottom half. Then remove the screw at the top of the points cam and remove the cam. Then lift out the springs and weights. Now you’ll see the stamped number on the action plate.
The number in the photo below means it provides 14 degrees of total mechanical advance (at the distributor) or 28 degrees of total mechanical advance at the crankshaft. That makes it an XK120 or XK140 action plate.
The DVX 6A distributors used in the early Jaguar sedans, typically had action plates stamped 17, giving 34 degrees total mechanical advance at the crankshaft. (However, in my collection I have one action plate stamped 21 degrees - but I suspect it did not come out of a Jaguar distributor.
Tony, I’m almost certain the weights were the same in all these DVX 6A distributors. But different springs, action plates, and vacuum capsules were used for different model Jaguars.
Additionally, the points cams were eventually updated from “standard” to “high lift”. With the standard cams, you set the points gap at .010 - .012. With the later high lift cams, you set the points gap at .014 - .016. If you provide the measurements across the “peaks” and “valleys” of the points cam, I should be able to tell you whether it is standard or high lift.
An update, I feel a bit stupid, as I did find stampings once I dismantled it.
They were faint and small, and hidden behind the vacuum capsule, nothing like the earlier ones with very clear obvious stamping on the body face
This one has the following designation;
DVX 6A 40372A GC53 9/55
Vacuum capsule end has 4/18/12
Stamping on the action plate is 15
My parts manual call this out as correct for late MK7 or early MK8
I have a question Mike, (or anyone else).
After marking most parts for re-alignment, in a moments inattention, I lifted and twisted the part in below diagram marked 'Cam"
The Cam has a cutout to mate with the rotor button, and can be installed 180* out
In my opinion, this would cause the wires to be 180* degrees out, as the rotor would be 180 out from offset dog ?
Luckily I was able to observe on the DVXH unit, that with the cam cutout facing me, the “wider” side of the offset distributor dog was on the right, and that is how I assembled the DVX
You’re right about the spark plug wires being 180 degrees out depending on how the points cam is oriented. Below is a diagram showing the “standard” plug wire setup for an XK engine.
If the DVX distributor is installed according to the diagram, with the rotor pointing to #6, then the “wider” side of the drive dog offset will be on the right in my photo below.
One reason I asked that question is because, over the years, and there was a few recently, confused and wondering if the drive gear had been assembled 180 out, with all sorts of gruesome engine surgery needed
I say just swap plugs wires and make a note of the situation
However, swapping this cam around would be an easy “fix”
Fiendishly bodgy though, dizzy put together all wrong, be very hard to detect for any future owner or technician (although they may never need to know, as it all should work)
I will double check your pic tomorrow on the cam orientation
If the plug wires are out 180 degrees and you don’t want to disassemble the distributor to flip the points cam, another way is to drive out the pin for the drive dog and flip that 180 degrees. I’ve done it both ways in the past.
I am not sure why pan off engine surgery was suggested, but presumably there must be a circumstance where that is needed to make everything fully right ?
I had to fix a blown head gasket on my first Jag, and managed somehow (dont know how) to assemble 180* out, I think I may have used this list to work out the possible issue and drove the car for about 15yrs with the plug wires reversed
Eventually I took the head off again and rectified it
while I have your attention, is that drive pin tapered, meaning it can only be driven out one way ?
Thanks for your astute reply, when I checked, I found I had assembled it backwards, despite having a similar one to copy, so have now corrected this
I took it apart but did not take digi cam pics, or mark certain parts with nail polish, but did scribe most parts, I was watching sport on TV, chatting, and it was night
The weights and springs can easily fall out, and they can also be put back together various incorrect ways
I have had them apart before, and its super important to mark everything and take pics
Given how easy it is to install the cam backwards, I suspect that is most likely the issue with individuals who have taken the distributor apart and then find themselves 180 out