<VV> Helicoil Advice

[Todd Miller]

Hi Folks:
 Looking for a little advice with helicoils, and to be honest, this isn't directly related to corvairs, other than I know many of you have had experience with having to use these with aluminum corvair engines.  The offending issue is on my son's 1986 Corvette with an L98.  We changed out the leaking water pump, and were concerned about the thermostat as well, so we attempted to remove the two bolts in the thermostat housing.  As these may not have been out since the car was built, both bolts sheared off.  One loosened a bit, and broke off when we tried to tighten it back up.  The other broke off trying to get the bolt out.   A friend tried to Mig weld a nut on the end of the broken bolts to try and remove them, but couldn't get enough penetration in to make it hold with any strength.   So, we are thinking that the only fix at this point is to try to drill out the steel bolts from the aluminum manifold and then put in a helicoil to be able to hold the new bolts for the thermostat housing.  Any other ways to do this?  Any advice on drilling out the bolts and using helicoils? Thanks for the help. Todd in TX69 Monza Convertible65 Corsa Turbo Convertible(Haven't had to drill out and helicoil anything, yet)