firewall stud - drilled hole - next step help please

(did search, but couldn't find any info for drilled hole options)


so I'm on the home stretch of my APN header install, just finishing tapping the threads & throwing the new one on-patting myself on the back thinking of how proud my wife is going to be of me..until- what?, my tap won't go into the last stud hole?? What I originally thought of as a just a missing stud turned into a broken one deep in the head -(stupid)

..so, I center drilled all the way through the broken stud with the biggest bit (15/64) that the firewall & angle drill would let me, PB Blasted in the hole & that's where I'm at. So whats a good next move? (here's what I'm thinking

1. try Eazy-Outs, using extreme caution not to break them
2. use progressively bigger taps & work my way up to the one I used (3/8-24 I think) for the rest of the holes
3. Figure out a way to use a HeliCord (can't get the big bit (27/64) back there though, unless I can find a short one somewhere?)
4. try Eazy-Outs, using extreme torque until something gives
5. bolt on the APN like nothing happened!

any advice would be greatly appreciated - thanks!

9t3country said:

(did search, but couldn't find any info for drilled hole options)


so I'm on the home stretch of my APN header install, just finishing tapping the threads & throwing the new one on-patting myself on the back thinking of how proud my wife is going to be of me..until- what?, my tap won't go into the last stud hole?? What I originally thought of as a just a missing stud turned into a broken one deep in the head -(stupid)

..so, I center drilled all the way through the broken stud with the biggest bit (15/64) that the firewall & angle drill would let me, PB Blasted in the hole & that's where I'm at. So whats a good next move? (here's what I'm thinking

1. try Eazy-Outs, using extreme caution not to break them
2. use progressively bigger taps & work my way up to the one I used (3/8-24 I think) for the rest of the holes
3. Figure out a way to use a HeliCord (can't get the big bit (27/64) back there though, unless I can find a short one somewhere?)
4. try Eazy-Outs, using extreme torque until something gives
5. bolt on the APN like nothing happened!

any advice would be greatly appreciated - thanks!

Click to expand...

If you have any MRO (Machine Room Operations) supply houses anywhere nearby, you can get rather short drill bits - I think they're "screw machine" bits, but don't hold me to it. However, they run about half to two-thirds the length of regular drill bits, so that may be an option. Use them with an "angle head" or "close quarters" drill, and you can get them into the damndest places...

My solution wasn't very elegant (on my old 87). After drilling out the front and getting lucky and hitting the exact center with progressively bigger bits and then being able to clean the stock threads out with a pick. I decided being lucky twice and especially in the rear wasn't going to happen.
I drilled the old stud down a bit, ground one end of a new stud to a cone, chamfered the hole, welded the new stud to the head (and somewhat to the old stud), chamfered the manifold a little and cleaned the weld up a little with a Dremmel. I welded the stud in with 4-5 spot welds. It held for about 6-7 years until the 87 was rolled.
On my new to me 88, I just left the front and rear busted off (from the dealership) and figured if it ever gave me any trouble, I'd (try to) fix it like I did the old 87. Or whenever I had to pull the head off in the future. or whatever happened first, manifold sealing problems or head trouble.
I really can't remember a manifold (intake/exhaust) ever leaking in the front or rear, they most always leak someplace near the center.
I'm pretty darned good at drilling a straight hole freehand (I've seen few people better), but I see little chance of success doing the rear.
On a buddies front manifold stud (he had already tried to drill it out and failed), I drilled the hole the next size bigger (metric) and rethreaded with a blind hole tap (stubby square end). Worked out well, we got enough threading to hold a stud securely in place.
Lathe drill bits come in a variety of lengths.
I keep a selection of brass nuts, especially, to replace the manifold stud nuts with. They get the job done, though they are pretty darned soft.

Try the ez outs. If it doesn't work, you could either:

1)drill smaller hole in stud and tap with smaller fastener
2)weld new stud on
3)yank motor and do it right

keep us posted

well, I went w/ option #1 (drilling hole in stud)....too scared to breake an Eazy-Out.......so I got a 15/64th drill bit back there (biggest one I could) , which allowed me to tap a 1/4" -20 hole & just bolted it down w/ a grade 5 1 1/4" bolt. I hope it holds!!!

thanks again for the advice!

This is not a joke:
Ask at your local machine shop supply for a left hand drill bit. (about 3/16) You also may be able to order them from a competent hardware store(not Home Depot)

They are short reverse cut drills. You run the drill in reverse while drilling. When you are drilling the center hole in the broken stud, about 1/2 the time, the bit will catch in the stud and back it right out of the hole. If it doesn't work, you have the center hole to hit with the easy-out.

tbburg said:

This is not a joke:
Ask at your local machine shop supply for a left hand drill bit. (about 3/16) You also may be able to order them from a competent hardware store(not Home Depot)

They are short reverse cut drills. You run the drill in reverse while drilling. When you are drilling the center hole in the broken stud, about 1/2 the time, the bit will catch in the stud and back it right out of the hole. If it doesn't work, you have the center hole to hit with the easy-out.

Click to expand...

X2

I've had decent success with left hand drill bits.