Exhaust Stud Heli Coil Pulled Out, Wou is me, Help! Correction Time Sert came out Options

[913B]

So the continuing saga of fitting the SS heat exchangers continue. I somehow pulled out the heli coil repair on the exhaust stud. The coil measures 9.5mm OD.
I suppose I need to re-tap the hole with a step stud.

So what size step stud should I use ?? M8 to (M10 or M11) ?
Where would I find such a stud ?
Is it do-able, drilling and tapping from under the engine ?
How the heck am I going to keep the bit and tap straight and not F/up ?

Man it never ends with old cars...... (IMG:style_emoticons/default/ar15.gif)
Thanks in advance for everyones help !!!! I really appreciate it.
(IMG:style_emoticons/default/beerchug.gif)

[HAM Inc]

You won't like this, but read it anyway. Remove the head and have it welded, machined, drilled, and tapped. There's a REALLY good chance the threads and inserts are going away because the head is cracked. Be sure they fix ALL the cracks. Plan on spending a lot of money.

BTW, there's NOTHING wrong with Helicoils if they're used as intended. They WON"T fix weakened or cracked base material, nor will any other brand/type of insert.

The Cap'n

Everything The Cap'n said is correct. I've seen a gazillion of the cracks he describes. That said, I examined the photo and it appears that you may just have a stripped boss. Hard to be 100% sure, but that is my hunch.
And there is nothing wrong with Heli-coils if they are installed correctly. The biggest mistake is poor threading, regardless of the insert type. It's a touch task laying on your back to get it right. An unsteady hand will make a larger thread.
The biggest drawback to the heli-coil is that it can be difficult to install in certain situations, like this one.

If you have been living right and you do a perfect insert installation the unit may just stay put. If it doesn't you are facing removing the head.

I can sell you a M10 x 8 step stud. My supply of the damn things is dwindling but I can spare one for a forum member in distress.
It will be M10-1.5 x M8-1.25

I may be wrong about this, but I believe the EZloc requires a larger hole than the time-sert or heli-coil. If that is the case I would not consider it for this job as you are about out of boss material.

A bit of advice that may sound counter intuitive, but trust me on this. Before you install whatever insert you decide to use slather both sides of that baby with copious amounts of copper anti-seize. Copper because it will stay put at higher temps without turning to paste like the silver kind. This will help keep the threads from corroding and increase the odds that the insert won't pull out over time.

The Time-Sert will be much easier to install in this situation than the heli-coil.