Stripped Exhaust Riser Stud!? How to repair - 5.7 Mercruiser

[the force]

I installed new exhaust risers, and had a bracket coming off one of the studs for my coolant overflow bottle. Apparently that 1/8 or whatever was too much and I stripped the threads in the manifold (was using a torque wrench though no idea how accurate this for 33ft/lb). The Mani’s are only 2 years old so I prefer not to need to purchase a new one.

I’m not sure removing the bracket and cleaning threads with a tap and die will be enough to hold… any advice? Longer stud (grade recommendation if this is possible), thread repair insert (which type), etc. this is definitely not my area of expertise.
5.7L mercruiser is the engine.

 

[terrin]

I installed new exhaust risers, and had a bracket coming off one of the studs for my coolant overflow bottle. Apparently that 1/8 or whatever was too much and I stripped the threads in the manifold (was using a torque wrench though no idea how accurate this for 33ft/lb). The Mani’s are only 2 years old so I prefer not to need to purchase a new one.

I’m not sure removing the bracket and cleaning threads with a tap and die will be enough to hold… any advice? Longer stud (grade recommendation if this is possible), thread repair insert (which type), etc. this is definitely not my area of expertise.
5.7L mercruiser is the engine.

Probably need to take Mani off and size up to next thread size then drill the riser hole to the same size.

 

[ship happens]

You can't go up a size. Just replace the stud.

 

[Offshore]

Heli-Coil is a good brand for thread inserts but if the manifold is cast iron you are going to need a drill and tap to be made for that.

 

[seachicken]

So you stripped through stud or the hole the stud threads into? If it's just the stud then replace it by threading it out with vice grips or similar, if it's the hole it's a different game.

 

[the force]

So you stripped through stud or the hole the stud threads into? If it's just the stud then replace it by threading it out with vice grips or similar, if it's the hole it's a different game.

Yeah I wasn’t very clear, the stud is fine it’s the threads in the cast iron manifold that pulled. Not realizing at the time but must have ran out of stud length due to the additional bracket and only been 2-3 threads in.
I’m not sure how deep the threaded holes are in the mani, I’ll check tomorrow and perhaps if deep enough I can go up 3/8 or 1/2” in stud length to get enough purchase.

 

[the force]

Heli-Coil is a good brand for thread inserts but if the manifold is cast iron you are going to need a drill and tap to be made for that.

Didn’t realize there was a different drill and tap for cast… thanks for that tip. Depending how much effort this takes I may just need to buy a new manifold for $500

 

[Samnjoe]

Run a bottoming tap into the hole as far as it will go. That will tell you how much good thread you have left. Use a longer stud and run it in as far as it will go. If you stripped it out at 33 pounds you can't have been very deep.

 

[the force]

Closing the loop on this one, got out the caliper and took measurements for half an hour. Had more good threads remaining in the hole then what the other 3 studs were threaded in. Bought a longer stud, ran a tap in, vacuumed out shavings and double checked fitment would work out w/o bottoming the stud out.
Installed everything, took her for a run and retorqued, seems to be good. Thank goodness, seems to have been easier than I initially thought. Thanks for the feedback all!