Well another problem. I had broke the header bolt off inside the head of my 327 1968 on the drivers side that holds the alternator bracket. It was about a 3/8 normal header bolt,  and I had to drill it out to 1/2" and rethread it. For some reason I cannot get the new bolt tight enough to pull the headers against the block so as no exhaust leaks. The bolt will not tighten enough. I am not familiar with HELI Coils but I think that is what I need. And how much trouble is it to install a HELI COIL. Any suggestions on how to tighten the manifold bolt so as to hold the alternator bracket and also seal off the gasket on the headers.

If you were able to drill/tap the hole to 1/2", then you can certainly install a Heli-coil. You will need to drill it again to a slightly larger size, then screw in the Heli-Colil insert. Just get a Heli-coil kit for the size bolt you are using.
Be vewy carfuwl drilling there...you can easily go into the water jacket...stop drilling as soon as you hit the bottom of the hole that is already there.

You may want to look into putting a metric bolt in there..the size up would be less or the same size as the hole already drilled..unless the bolt has an extension on it for a bracket..that would make it difficult to find a correct bolt..you may get away with borrowing a heli coil set from the machine shop you got the engine done at..they are expensive and you probably will never use it again..do be careful drilling in there as it may ruin the head.. Rich

if you drilled the hole out with a half inch drill bit you drilled it too big for a half in. tap, when ever you drill a hole for a centain size bolt you drill the hole smaller than the bolt to allow material  left so you have material to cut  the threads themselves, I think thats why you can't get the bolt to tighten , there's no threads, if you do anymore tap work make sure you have the correct drill bit size for the tap your going to use and that goes for heli coils to.

|UPDATED|8/22/2011 12:30:39 PM (AZT)|/UPDATED|

Maybe an easy-out will work, if you can get a good bite in the broken stud. Use lots of PB. Might give that a shot.

Gary I think he has the broken one out already. And yes there is a guide as to what size drill / tap combo to use.

I BELIEVE RICH'S NEXT OPTION IS A 9/16" BOLT AND THATS SCARY, WENT TO AUTO PARTS TODAY FOR SOME THINGS AND ASKED THE COUNTER GUY  IF THEY MADE OVERSIZED OUTSIDE DIA. HELI COILS FOR A 3/8" BOLT HE LOOKED IN THE BOOK  AND COULDN'T FIND ANY, I KNOW RICH DOESEN'T WANT TO HEAR  THIS BUT THE ONLY NEXT OPTION I CAN THINK OF IS PULL THE HEAD USE LOCKTITE STUD MOUNT AND PRESS IN A SLEEVE OR PIN AND TAP  IT FOR A 3/8" BOLT, THIS IS A JOB FOR A MACHINIST, ANY OTHER IDEA'S? 

|UPDATED|8/23/2011 4:45:35 PM (AZT)|/UPDATED|

There is a product called "Threadsert", that is similar to a Heli-coil, but it is basically a chunk of stainless, or "regular" steel, that is threaded on the outside, and the inside. It takes a larger sized hole than a Heli-coil, so that might be an option. I've used them, and have a few still in my toolbox, but nothing that large. I think all of mine are 1/4" & 5/16".
I'll see if I can find a link, or something....