Helicoil on Exhaust Manifold Stud Failed - Drill/Tap to M10?

[High PSI]

So the head was helicoiled before, and just now while torquing the studs (to only 26 ft-lbs!) one failed and pulled out of the head clean with the head threads.

I think on the 7-bolts these are M10? Can I just drill/tap to that?

 

[Vegas Smith]

Yes, that's an option. Remember that you'll have to drill the manifold hole larger.

 

[greddy_1700]

Or look into a timesert. Might still be an option depending on what size it was already drilled and tapped for the helicoil

 

[High PSI]

Yes, that's an option. Remember that you'll have to drill the manifold hole larger.

Actually, I don't think that's going to work as the hole looks like it was drilled too large for the helicoil.

Or look into a timesert. Might still be an option depending on what size it was already drilled and tapped for the helicoil

I'm thinking I'm going to get Big-Sert #5812 kit as another user outlined here:

https://www.dsmtuners.com/threads/exhaust-stud-repair-big-sert-tips.522654/

 

[greddy_1700]

Perfect, I assumed they would make timeserts in a larger od, just didn't know they called them big-sert. Definitely update and let us know your experience as well once its complete.

 

[steve]

I think on the 7-bolts these are M10? Can I just drill/tap to that?

I thought it was only the two end studs that were bigger, not the top and bottom ones.

 

[High PSI]

I thought it was only the two end studs that were bigger, not the top and bottom ones.

Correct. When I went back out and looked at it I noticed that it was just the two bottom studs that were larger.

Got my Big-Sert kit, drill and tap guides and some warm weather forcast so I'll be giving this a go over the next couple days. Will update this thread with how things went.

 

[steve]

I forget which studs are close to oil channels, i think it's the top middle, but just be careful....