Hi folks, while tightening exhaust manifold nuts, one stud 'pulled out'. Small steel crescents fell out and were wound tight around the stud, evidence that a repair had been made previously. I figure that I should drill and tap the hole for a step stud. The engine is in the car, the car on a Quick Jack.

Any tips on drilling out and tapping the hole while under the car. As I will need to buy a tap, exactly what type/size should I get? I read on another thread that someone made a drilling jig for this purpose. Would something like that be needed/advisable for this job? Does anyone have one to lend?

Also, what are the torque specs for the stud and nuts?

My personal opinion, they are a bit pricey but Time-sert has been what I have used for alloy thread repair. It holds up.

https://www.timesert.com/

I used a time-cert and a step stud on one that I pulled and it’s held up for many years with no issues. Did it with the engine in the car. Just go straight and slow with plenty of cutting oil, and not too far when drilling!

As far as step stud size, I think I used an 8x10 because the threads were really buggered and it looked like someone had been in there before. I had a hard time finding the proper step stud at the time, maybe they are easier to find now.