I think I maybe got lucky for a while... Even if not, I have three spare B18 heads if I did really screw this up...

So... last time I was stopping vacuum leaks and replacing gaskets, I managed to break my forward manifold stud. Having limited time and no decent screw extractors, I left as was for the week and got back to it this weekend when exhaust leakage was really becoming a problem.

The stud was snapped off at the surface and required that I drill a pilot hole to get an extractor in there.

Nothing went well... The distance from the head to the inner fender is such that I could not get my drill in there at a proper distance. And then the damn thing skated off center. Then the screw extractor made things much worse.

Since this has worked for me several times before, I decided to re-tap the hole for a 5/16" stud. That went sorta okay...


The main issue here is that when I was enlarging the drill hole the drill went in at something other than perpendicular and suddenly bored into an open area. Nothing came pouring out (like coolant or oil) so I'm pretty sure I did not pierce the super important parts of the head...

I used a probe to measure the depth of my new hole and compared it to one of my spare B18 heads. It seems that at maximum, the drill bit could have gone as far in as the far edge of the headbolt tunnel. From the direction, my best guess is that the drill went into the headbolt tunnel, but skipped more towards the #1 exhaust tunnel side of the headbolt tunnel.

I removed the thermostat to look for signs of piercing the coolant reservoirs and water-jacket, and was greeted by a lot fo coolant bubbling up. I reasoned that if there is that much coolant under the thermostat, then it woudl have come pouring out if my stud hole had pierced he jacket. So...

After I finished the shallow tap for the new stud, I buttoned everything back up and test drove it. Everything seems fine. No leaking fluids, no overheating, no weird engine noises.

I think I got off lucky, but I'm thinking that when time allows (or necessity requires), I should probably pull the head and at the least replace that headbolt. If I really screwed it up, I can always swap on the head from the car's original motor (which needs to be re-assembled) or I can just drop on the 67 B18 head from my Wagon's original motor.

At such a time I could remove this head for a more thorough inspection, and maybe a helicoil to restore the proper angle to the #1 stud.

Fun stuff. Please let me know if you have any theories on my catastrophe.
If there was a *far* easier way of getting that stud out, also please let me know. I do not ever want to repeat this experience!