Right, so, my head had to come off again. Nearly done, but 1 stud won't fully come out. It won't unscrew any further, but it will go back in. Somehow it's stuck so what I want to do it hold the stud very tight and unscrew the bolt that's on top.

Question: How do I hold the stud so tight I can unscrew the head bolt?

 

With the head in the way, I dont have any idea.

The head nut, as in the Dome style, can bind to the stud due to no anti-sieze, or lack of proper spacing between the head and nut, which of course, is of little help now.

All I can think of this early in the morning, is to unscrew that stud as far as possible, which will leave a gap between the head and the base of the dome nut, and then dribble some penetrating fluid down the stud. This "may" provide enough lube for the stud to thread all the way out. That engine should be what is known as a "short stud" engine, where the studs only thread into the top deck of the engine block.

OR, coffee is kicking in, cut off that dome nut, using a dremel or similar. redress the threads if they get slightly damaged. Dome nuts are easy to find.

 

I've had it off 6 months ago and the nut itself came off then. I ruïned the thread below the nut with a wrench. Might not be an option.

 

I would sacrifice the nut at the very least.

Threads can be redressed, and some very sad threads can be saved.

Last option for me would be to cut the stud below the nut, get that head off and out of the way, remove the remains of that stud, and simply fit a replacement stud, either new or s/hand.

If it was out 6 months ago, whatever is giving grief simply cannot be too serious. Annoying, yes, but it can be removed, and sometimes the long way round is the most fruitfull.

I have had issues getting the studs out of V12 blocks over the years, and that block being alloy, time must be on your side, or it simply becomes a fancy wine rack for 12 bottles.

There is always a way.

 

So, just to be sure before I cut the nut off I tried it one more time, this time adding 2 thingys to the clamp to increase the hold while my dad turned the bolt off and it worked.

Not so much fun: The cilinderwall looks worn and I can see brass/copper stripes?

 

Here's a thought/2 cents. If there is room, get two shallow or skinny nuts and screw them on to the top of the stud, lock them together=1 left/1 right and them hold them in place(holding the stud) and then break that seal/lock on the original one.
IF THERE'S ROOM FOR TWO NUTS(skinny)

 

The brass/copper stripe is rust from the piston ring > oil scraper. My engine is early March 1969 so must be original. It has over 150k kilometres. Today I got a engine from a Dutch forum member with oversized pistons that is basically brand new for free, just need to swap my head and crankshaft into it. Will take me a while.