Hi, just a quick question regarding the thread pitch and size for the camshaft sprocket bolts on an XJS V12.

The bolts that are currently in there seem way too short for their application with only 2 or 3 full turns of thread taking up the load. As a result the threads in bolts and cams are a little stretched!

I’ve ordered new bolts but want to re-cut the threads in the cam before I put them in. Unfortunately my limited array of UNF taps don’t match so I’ll have to buy a new tap for the job. If anyone knows or can measure the thread diameter and TPI it would be greatly appreciated and will see my XJS once again live!

From what I can gather the bolts that are in there aren’t original. They are drilled for wire retainers rather than retaining tabs. Probably earlier XK specific rather than XJS. The new bolts are about 3/16 longer than those that were already installed.

Thanks for any help you can offer!

Richard.

 

I think I may have found the correct size tap! Can anyone confirm 5/16 x 32TPI?

 

You will get limited eyes on you quite specific query posting here

If you post in the XJS section your audience is global and with that more chance of an answer

 

Steve is right,

BUT

I saw it.

My scribblings from doing too many V12 cam timing tasks are:

Setscrew 0.375" X UNF & 0.625" long. C33918 was the part number, and I ALWAYS fitted new setscrews whwever in that area, NO exceptions. They cannot be too lomg, or they will clobber the head hehind that flange. I agree, not much in it.

Some I have dismantled have had a thick spring washer under those heads, are NO NO for me, as those washers are quite a lot thicker than the OE lockplate.