Try as I might I can’t find a torque spec for the 4.2 engine head studs in any of my ancient and forbidden Jaguar tomes or the internets.
Does anyone have that info or is it just mechanic-tight? That’s how I’ve always done it but I got me a new, fancy 7/16-20 stud installer so I figured if there was a torque spec I’d do it that way… all precise like a guy in a white lab coat instead of like a guy with a bunch of Jags up on blocks and an engine hangin’ from my front yard tree.
Hi Mike, when I refitted the head on our long stud 4.2l I was advised to make up a plug tap on a long T bar and scrupulously clean out the threaded holes at the bottom of the block. Once all the crud was removed - multiple iterations - then checked that studs were fully bottoming. Then bottomed the studs including Never Seize or similar, double nutted the top and leant on the spanner - “mechanic tight”. This way ensures room at top of domed nuts - with single washer. Fitted head and wound nuts to 54lbs.ft (apology for any failing memory). Touched up after 3 months, this approaching 3 years ago. This is all hot air if you have a short stud, of course. Paul
if the head need to come off later for a gasket etc, what is to stop the long stud unwinding with the nut, and then scum fall in the hole, and you have a big problem?
the female hole threads tend to deteriorate due to corrosion with the male stud thread, water ingress…this can be a block-killer
instead of copperslip, and “finger tight”, I am wondering if the weakest thread locker, such as purple lockite might kill 2 birds with one stone?
ie seal out moisture, as will copperslip, but hold the stud in tight enough to enure it does not screw out with the nut, (purple can be undone with hand tools and no heat)
the long studs are often rusted in, hard to get out, and can be rusted near thru at the base
I use double nut to R&R the studs, and have removed a couple of broken of stubs, the female hole thread is a worry with old blocks
Hi Tony. I guess I decided that following all the horror stories about seized long studs - especially those that “neck down” from rust and break down in the water void - my first task was to enable the stud out. It was a “heart in the mouth” job when I pulled the head and then fought to get the rusty studs out. The T bar plug tap did a great job of cleaning out the crap - I think we have to plan for this job in these engines as a likely eventuality. They weren’t “finger tight” going back in I really leant on the spanner and made sure they were tight and bottomed. Next time if some come out, stud and all, I will deal it as I did on the last occasion (for a couple of them at least). Just pleased to get them out! Paul
One thing I did notice, on an engine rebuilt by Jag pros, is the head stud/nut junction is smothered with copper anti-seize, far more than I would have thought to use
I did the same (as advised by a pro) - and still had one weep collant for a while until it settled. I think we all think similarly, there are no shortcuts on these engines. Paul