My car is 1977 preHE v12 xj-s. Engine is now out of car,
the cylinder heads are now off,
the cylinder head studs look rusty. I thought to get them electroplated in zinc and passivated then reuse them. I know this company that does this for acceptable cost and the parts they return to me always look shiny bright beautiful. Would this process interfere with torque specs or otherwise be bad? Or considered acceptable?

I did this to the crankshaft pulley bolt too, intend to do it on lots of bols if it's okay

Thanks
Janos

 

Head studs like to stretch under torque. The spec for them would need to be measured against. They only stretch so much before they snap. Especially if now you involve corrosion. Disclaimer: I've no V12 Jag experience but just general mechanic knowledge.

 

Modern cars use Torque To Yeild head bolts. The XJ-S does not.

The ROM's Instructions are to replace any that show signs of corrosion. If they're rust free you can reuse them.

 

And there's the right answer lol. I gave it a shot.

 

This video gives the do's and dont's of reusing studs on the V12.

Jon

 

I am guessing you have not taken the studs out of the block yet.
I they are in good condition I would just leave them in the block.
They can be very difficult to remove, and you might strip the thread in the block.

As long as you use a good inhibitor in the coolant, and replace it about every 5 years, the studs will not deteriorate.
Unfortunately many owners do not do this.

 

Stop, STOP, STOP!!!
You do realize only the tip of the stud will show. Plus zinc is a soft metal and doesn’t provide lasting protection.
Buy some Chrome acorn nuts . Make sure the not bottoms out before the threads stop. If it doesn’t reach all the way down buy some chrome washers. ( use a piece of Toilet paper over the acorn nut to keep it from marking the chrome).

I’m a racer and when I want to dress up the engine I buy 12 king AN. Nuts. It really looks racy.

 

I use two nuts, fasten then against one another on the stud, then turn the lower one with a wrench. This method was able to get the large studs out. The small ones, I undid 2 of them with an impact wrench, I have a battery powered impact wrench, seemed to fo it with ease. The impact wrench can only attach to the top one of the 2 nuts. I am now waiting to get the correct socket wrench for the impact gun, I only have socket wrenches for hand use and SAE inch size tool are a rare thing in this part of the world.