Good day,

I was hoping that I could get some information on some bolt threads for an AJ6 and v12 from an XJS.

I need the thread info for the front timing cover plate to block on the AJ6

And also the front timing and top cam cover plate to block for the v12.

Can anyone help me out with what thread bolts these require?

Thank you so much.

Regards,
Matteo

 

I have zero clue, if it is on something you own, why can't you just guess and buy 3 or so in the range you think it should be in to see which size it is exactly? Or buy a thread gage? Is it the length into the block you are more concerned with?

Sorry for not being so helpful, perhaps someone knows off the top of their head.

 

The Palm book has some detail on the fixings, but in the case of my emgine it was not entirely accurate. On the V12 engine Jaguar changed during the 1980s from UNF and UNC to metric, but not all of them. As SS said, it is safest to undo one and try a few nuts on it until you are sure which thread fits. Be very careful, as into aluminium it is very easy for a UNC bolt to turn quite easily into but nevertheless ruin a metric thread in the ally. Any studs are likely to have a coarse thread on the block end and a finer thread on the nut end.
Greg

 

Thanks for both of your replies.

Sadly, I do not have any original bolts, or else I'd just measure those. I have lots of metric and standard bolts & taps that I test fitted, and none of them seemed to screw in without leverage..... I got the block bead blasted recently, so my first thought was maybe there is debris clogging the thread path, but I made sure to get all of it out with compressed air and whatnot.. So I wanted to ask before I tried to put "force" into tightening a bolt.

Yeah, aluminum is very soft... At first I thought it was 5/16 course, which seemed to fit OK, but I soon realized I was stripping the threads..

I found out what thread the AJ6 timing cover used.... M8 1.25 IIRC...

I just need the V12, so if anyone knows this offhand or can find out with little stress, please let me know.

I know it's quite a silly question to ask, and I apologize for that.

Thanks,
Matteo

 

For the V12, if you post a photo or a diagram of exactly which bolts you mean, PLUS your car details (year, model, engine no.), I will undo the relevant bolt from my spare motor, assuming it is a compatible motor and that I can just undo one with no further disassembly needed, and see what it is.
Greg

 

Thank you Greg. I'll post the photos below, bolts needed will be circled in red.
As far as car details all I know is the engine no. but not the car year. 8S4761LA 71-79 XJS 5.3 NON-HE 7.8:1 CR
I picked up the fully dressed v12 & aj6 for $70 on CL... Soon they'll be a "matching" set of tables...

Thank you,
Matteo