Helicoil exhaust manifold bolt hole

[bohog]

I have to Helicoil 1 of the exhaust manifold tapped holes in the head.

Do I have to put some sort of sealant on the thread insert before installing into the head to prevent coolant from leaking, or will the insert alone be enough to seal?

 

[62MAX]

The insert won't make,use a good sealant on the insert and stud.

 

[1968rick]

Head on or off.....I dislike Helicoils. prone to failure when the stud or bolt are removed.....Look for a thread insert, or make your own.....Thread inserts are threaded to the original size internally and a couple of sizes larger on the out side. Drill and tap the head to the outside diameter and thread the insert in and jam it into the bottom of the threads , then cut any exposed flush.

 

[coloradodave]

Head on or off.....I dislike Helicoils. prone to failure when the stud or bolt are removed.....Look for a thread insert, or make your own.....Thread inserts are threaded to the original size internally and a couple of sizes larger on the out side. Drill and tap the head to the outside diameter and thread the insert in and jam it into the bottom of the threads , then cut any exposed flush.

I've used Heli-coils for many years and have yet to have a problem with them. In fact I did the 2 front-most end exhaust manifold bolt holes in my iron heads. These do go into the cooling passages. Instead of using my usual ARP thread sealer I used a good amount of red Loctite on the exterior of the Heli-coils and then let it set-up for 24 hours before bolting up the headers (no room for studs) and adding coolant to the system. No leaks in the last 2,500 miles.
Different strokes for different folks...

 

[cryplydog]

If its just a general repair I would just clean out the existing threads with a 5/16 bit gently and then retap to 3/8-16 and also enlarge the hole in the manifold. If you are using alum. heads with blind holes heli coil works great if installed right. If iron heads I then use a plumbing compound that is non hardening called RECTOR SEAL. wondefful stuff and its use is for steam-gaseous prods.-water and just regular plumbing. easy fix for a mopar guy. I think those thread/hole dims. are correct so make sure. I do many repairs like this.

 

[747mopar]

I've used Heli-coils for many years and have yet to have a problem with them. In fact I did the 2 front-most end exhaust manifold bolt holes in my iron heads. These do go into the cooling passages. Instead of using my usual ARP thread sealer I used a good amount of red Loctite on the exterior of the Heli-coils and then let it set-up for 24 hours before bolting up the headers (no room for studs) and adding coolant to the system. No leaks in the last 2,500 miles.
Different strokes for different folks...

Same here, I'm an industrial mechanic-machinist and have had nothing but good luck with heli-coils. Only failures Ive ever seen happened right off the bat from being installed incorrectly (not deap enough hole usually). As for the question no sealant is needed although a little red loctite doesn't hurt, putting rtv on the stud will seal it just the same as it would normally.

 

[miller]

Yeah...on my wore out 906 heads, had to helicoil all the exhaust stud holes, since all but one were too loose. Red loctite between the holes and the helicoils to help seal it.