Cylinder head exhaust stud issue

[dom14]

Hi Guys,
Vehicle is an RB30 Patrol on carby.
While I was putting the exhaust manifold back on the cylinder head, I ended with a problem I wasn't expecting.
I had to pull the exhaust manifold out to do a welch plug.
Today I put the manifold back in.
Previously it had about five bolts. I replaced four of them with studs.
I was going to replace all the bolts with studs, but didn't realize I need five of them.
So, there's only one bolt that goes into the head to fit the manifold.
While I was tightening that bolt, I realized I had the thick washer and the spring washer reversed.
So, I started undoing the bolt to correct that. And it was getting harder to undo the bolt, but I didn't realize
it was a problem. I was having hard time getting the bolt out, but eventually managed to pull it out enough to find
out there's a spring insert was installed into the stud hole.
The spring insert was ruined by me pulling on the bolt.

I'm wondering how to fix this.
The exhaust manifold is fitted and all the other bolts are tightened along with generous amount of exhaust sealant to deal with any leaks.
Now, I have this issue.

I prefer if I can fix this without having to pull the exhaust manifold out again.

Any ideas, tips will be greatly appreciated.

[billyj]

that insert would be a heli coil(thread repair device) if your lucky just fit a new heli coil worse case drill and tap it out to a bigger size and fit a solid insert then drill/tap to correct size

[dom14]

that insert would be a heli coil(thread repair device) if your lucky just fit a new heli coil worse case drill and tap it out to a bigger size and fit a solid insert then drill/tap to correct size

Thanx mate. Hopefully I'll be able to get a new heli coil and screw it back in without having to pull the exhaust manifold out again.
It's a bummer if I have to 'cos I applied generous amounts of exhaust sealant to the damn thing.
And I was damn sure this is the last time I'm putting the exhaust back for a long time from now.
Couldn't be more wrong by the sound of it.

Where can I buy the matching heli coil for the exhaust stud?
I'll be buying a new stud from the exhaust guy.
Would he have these heli coil thread repair thingys??

Thanx

[Sharky1]

I'm not a huge fan of helicoils, especially in a semi high torque application. In all honesty your best bet, provided the manifold has enuf meat on it, is to drill out the the manifold if necessary & use a larger diameter bolt.

Or.........if this isn't possible then definitely use a stud on this hole & locktite both the helicoil & the stud with something like locktite 518 or similar. Don't overtighten this nut, ever!!!

[dom14]

I'm not a huge fan of helicoils, especially in a semi high torque application. In all honesty your best bet, provided the manifold has enuf meat on it, is to drill out the the manifold if necessary & use a larger diameter bolt.

Or.........if this isn't possible then definitely use a stud on this hole & locktite both the helicoil & the stud with something like locktite 518 or similar. Don't overtighten this nut, ever!!!

Thanx mate

That's exactly what I did mate, except I didn't have to drill the manifold hole or the cylinder head hole. Helicoil is a bit of PITA 'cos the manifold is already fixed to the head with exhaust sealant as well.
The size of the enlarged threaded hole on the head for the helicoil insert was 7/16". I couldn't find a bolt of that size with enough thread length.
But, I ended up finding a bolt in my bolt/nut box and cut it to stud and inserted it into the head with a mixture of epoxy & loctite red.
I left it for couple of days before tightening.
It's all good now. I could've done the same thing with a helcoil insert but didn't wanna pull the manifold out again.
Helicoils are bad news for bolts that need coming out too many times. I reckon that's exactly what happened.
I've been pulling the exhaust manifold out at least three times this year.
It won't be for a very very long time now.

BTW, exhaust nuts come loose after a while, even if I overtighten them. I think it's more to do with the gasket settling, rather than the nuts coming loose.