Frozen Head Bolts Universal 5411

[jimd333sail]

I am doing a piston ring job on my Mod 15/5411 engine and half of head bolts are frozen and had to be broken off. There has been water fifteen years ago and the head bolts have been used before, it appears. I'm going to weld a washer and nut and hoping to break out the remaining part of the bolt without breaking it off. They are protruding from the block from 1/8" to 3/8"....I'm using heat and cold and vibration.
My question is this: if I have to drill and extract the bolts (especially if they break again below the block deck...I've been told that if your drilling is off more than a couple of thousandths, you might not get helicoils or threadserts to work. Is that true?
Does anyone know if there is a jig that can clamp onto the block to center the extractor? Also someone told me about a product called "Drill-Out Power Extractor". Anyone use that?
Thanks, Jim

[tommays]

If the studs go into a wet part of the deck the helicoils tend to leak so its best to drill exact and save the hole

On my A4 gas after getting everything off i used the good holes to hold the head in place

Then got drill bits the size of the clearance hole in the head and drilled just a BIT to spot the hole and changed to the correct size bit

This was also a good way to guide the tap as they make extended ones

[jimd333sail]

I hadn't thought of using the cylinder head as a guide for centering the extraction process...will keep you posted, thanks, Jim