So tightening up the exhaust manifold studs after repairing my head gasket the nut moves onto the stud the stud does not turn but the nut moves closer to the head but it doesnt get tighter.

I think the stud is pulling out of the head somehow! I was using a torque wrench set to the recommended 34 ft/lb

Anyone know the size of these?

Can I drill out the old threads and use the next size larger stud?

 

See Schuyler's discussion on same issue. Recommendation was high end inserst.

 

Even a basic Heli-Coil would be fine for this application. It's liquid-cooled. Doesn't get that hot. Certainly nothing like the manifold to turbo joint.

 

well thats good to know. the inserts are like $80 because they require special tools.

 

this one here?

https://www.miataturbo.net/engine-pe...threads-81900/

Doesn't give much information beyond either using helicoil or timesert.

Can't do timesert way to expensive. A kit to fix my one stripped exhaust stud would be about $90 the actual insert is like $3 but you have to buy the special drill tap installion tool tap guide and all this other gubbins.

I think I will do helicoil.

Should I just go up to a M12x 1.25?

 

I'd stay with the original stud size. The size is fine, plenty strong. If you drill and tap for the larger stud, you'll still have a steel stud engaging aluminum threads and you may have to enlarge the bolt holes in your exhaust gasket and manifold. Hassle. Once you've put in the Heli-Coil, your steel stud will be engaging stainless steel threads -- no more issues.

 

Do not go up a size. It may lead to unintended consequences. If there was a need for a larger size, it would have been there in the first place. Us designers don't (usually) just pick fasteners at random.

Besides, a decent helicoil (done properly) will be stronger than the original threads anyway.

 

I assumed when doing helicoil you had to go the next size up since I thought you drill out the threads and then thread larger and put the helicoil in.

The stock size is M10x1.25 correct? It seems a hard to find size.

 

the helicoil is almost the next size up, but you re-use the original size stud.

 

I helicoiled one of mine and it is holding up fine.
Last header swap I discovered another one was stripped so I will repeat the process without hesitation. Borrow the tools if you can. That's what I did.

Note: the ones close to the firewall are a bitch. I could barely get the one I did straight with electric drill. A 90 degree air drill would have probably helped for clearance.

 

NAPA has metric Heli-Coil kits.

 

I will be shopping for heli coil kits. I wish I could just borrow the tools and buy the coils but it sucks not having friends with tools!

I guess if it takes $50-$75 to fix a hole then there isn't a way around it.

 

You could always take it off and to a machine shop for a professional repair. Might be a cheaper solution.

 

HelicoilS are junk, keencerts (threaded insert, positive locking) are not expensive. McMaster has them for about 4 bucks.

Who is paying 80 for time serts???

 

Probably someone assuming they "require" special tools. Though, I have been unable to find keen-serts/time-serts locally, and kind of forgot to order them. So I may be going with a helicoil this go round....

 

Not the inserts... The set. You know the correct drill, countersink thing, tap, installation tool and a handful of inserts?

 

you do need special tools. the insert needs to be expanded into the drilled hole which requires a specialized tool. also needs to be counter bored which also requires a special tool. unless you guys are talking about ez lok above. which are held in with loctite and you have to drill out to 9/16" for the proper size ez lok insert. the whole deal with these is yes you can install them with a scredriver but to make it cheaper they use standard size taps in this case 9/16".

why exactly do helicoils suck?

also I should add I bought everything I need for $22. drill bit tap coil threading tool installation tool and coils. heck of a lot better than $80 for insert.

 

 

dont know how I missed you guys were talking about keenserts. those still need to be drilled out quite a lot. the thin wall ones to m14x1.5 and if you like me dont have a tap set already a tap needs to be purchased. according to a test I saw on a 1/4" bolt those are stronger of course its a larger thread a keensert needs to be threaded into. and they seem a little easier to install.
I chose helicoil because I didnt want to have to drill out a big hole in the head and if the helicoil fails I can still do a insert.