Ideas on sealing header bolt?

Ever since I fired this new motor up with the w2 econo heads I've been having issues with the passenger rear header bolt leaking coolant. At first, it was trickling out a little bit when I used ARP thread sealant. I put it back in using copper RTV instead and I had no more wetness/dripping on the outside, but I was still getting occasional little puffs of white smoke out from around that primary almost as if it was leaking inside of primary. I pulled the header gasket out and it looks like it was wet all around the bolt and possibly caused the gasket to leak where the antifreeze softened it (which would explain the smoke trails).

Not really sure what to use at this point, anything thicker/more durable than RTV? Never had this issue before, and even the front header bolt which is also a wet hole never has any issues with just using the Arp sealant.. No cracks I can see around the port or bolt area, just seems like it's pushing out the threads. Could excessive pressure in the coolant system cause this? Compression test showed all cylinders within 5 psi of eachother but haven't done a leakdown yet.

Thanks!

I had the same issue until I put a can of Bars Liquid Copper in the radiator:

https://www.autozone.com/antifreeze-radi...aler/560508_0_0

I've also used RTV high temp silicone on leaky header bolts with good success. Make sure you're getting good thread engagement.

I use a can of Bars Leak in all my builds...
it should stop it

I use the silver solder,same results as the Bars Leak.No header gasket just high temp RTV.

An old pipefiter taught me a trick. Use Teflon tape making sure you put the tape on right so it gets tighter as you screw it in but then he would wipe a light coat of Teflon pipe dope on the tape. Works for me but I also use a stud whenever possible which really seems to help. I just hope your W2 Head isn’t cracked like mine was

that is what I would do, is get a regular OE type fine/coarse double end shouldered stud. You can shorten the outer fine thread end so only enough remains so when the nut is torqued, it is flush with the end of the stud as any more is a waste & hampers header fitment over the stud. & use some viscous sealer on the threads that go into the head.

Masters metallic pipe dope.

Indian head / aviation sealant on a stud.

I had this same issue with a set of 452's. Found out that the rear freeze plug had rusted and was leaking. I thought it was the header bolt not sealing. I couldn't see the rear of the head. I had the freeze plugs replaced with copper ones and have not had a problem.

I use the bars with a copper flake. Also have had really good results with alumaseal powder...🤘

I have 2 exhaust bolts on my Indy -1s that hit water. White Teflon paste. Been running the car 5 years, 500 passes. Never leaks.
Doug

Stud it with good ole hardening permatex.