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)

[Phoenix-MN]

Both myself and Phoenix914 have used the EZLOC with success, i used the M8 1.25 x 1/2" 13 also, I have step studs and helicoils but the EZLOC looked like the beefiest solution that i doubt would ever pull out. I have had many failures with Helicoils pulling out. EZLOC's are easily removed which i liked over the Timecerts but can be also be locked in place.

I used a hand drill on mine very carefully and wrapped tape around the drill bit to set the depth. The existing hole was my guide.

Ace Hardware or Hardware Hanks sells metric exhaust studs.

Yup, this is what I used (from McMaster Carr) They make them in several body sizes for different pilot hole sizes.

[Bartlett 914]

Both myself and Phoenix914 have used the EZLOC with success, i used the M8 1.25 x 1/2" 13 also, I have step studs and helicoils but the EZLOC looked like the beefiest solution that i doubt would ever pull out. I have had many failures with Helicoils pulling out. EZLOC's are easily removed which i liked over the Timecerts but can be also be locked in place.

I used a hand drill on mine very carefully and wrapped tape around the drill bit to set the depth. The existing hole was my guide.

Ace Hardware or Hardware Hanks sells metric exhaust studs.

Yup, this is what I used (from McMaster Carr) They make them in several body sizes for different pilot hole sizes.

I used these as well. You will need to grind the tap so it will thread deep enough. A bottoming tap may work. I have only plug taps so I cut mine down. These inserts may be bigger than timeserts. I have never used a timesert.