best sealant for head studs in block

[A Model Man]

I've traced a leak in my Model A engine to a small hole in the block at the bottom of the threads where # 7 head stud goes. The threads appear to be solid. I need to seal these threads to eliminate the leak but not permanently affix the stud so it can't be removed when the need arises. What would be the best sealant that can take the heat, seal the threads, hold the torque and still allow the stud to be removed? Preferably something I can get at the local parts store.

[Joe K]

Permatex No. 2 would be the classic method to seal.

Pipe dope might work. The old fashioned clay based (NOT teflon) would be best.


Of the two the permatex would be the more remove-able - and I expect would seal better.


Joe K

[100IH]

If the threads fit loosely to the threaded stud but your willing to see if you can get by without a thread repair insert, use the #2 and add a very thin ring of silicone or Right Stuff sealer below and above the head gasket. this is to seal coolant so as not to creep up the stud. Bottoming the stud won't have much affect as far as sealing the coolant. I believe that they are meant to be left 1/2 turn backed off.

[Pete]

I use high temp black RTV.
Apply some to hole. Coat thread on stud, screw in finger tight to bottom. Back up 1/4 turn. Let sit for 1/2 hour before torquing.

[Synchro909]

You could just put it together as is and put a little radiator leak repair in the cooling system. A few years ago, I was about 1,000 miles from anywhere when I noticed a small leak like yours. A teaspoon full of powder and I haven't touched it since.

[CWPASADENA]

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I agree with #2 Permatex


I have been using this stuff for a very many years to seal head studs with very good results.


Chris W.

[GOSFAST]

I usually post in the next section but this question just caught my eye!

We use the hard-setting #1 Permatex (#1C) on all our studded builds, we even use it for the head bolts that go into the water! Can't recall ever having a single leak either, stud or bolt?

Thanks, Gary in N.Y.

P.S. Even though it's considered "hard-setting" I've never really seen it get to the point where a stud can't be removed later on, unlike using Loc-Tite!

[A Model Man]

Thanks for the good advice. I have a pretty good selection of permatex products on hand so I'm ready to reassemble.

[rotorwrench]

A friend of mine used to dip the threaded end of the fastener into a container of Aviation Form a Gasket before installing them in an "into the coolant passage" fastener. It keeps the fastener from rusting on the tip and it seals the threads. As long as a person didn't wait too long about running it in then bolts could still be retorqued but they won't move much. Studs aren't a problem in that respect.

There are some more modern anaerobic sealers that might work better like Loctite 515.

[30 Closed Cab PU]

Permatex - Permatex 51813 Anaerobic sealer