coolant leaking around studs

[MikeDSmith]

I have completed a rebuild of my atomic four. I also added a heat exchanger. Both of the studs are leaking coolant. One of the studs had a helicoil installed. It comes out at the top of the thrmostat housing. Both the stud with the helicoil and the stud without are leaking. I've used permatex thread sealant, jb weld, permatix gasket sealant. During all of the atempts (six or seven) I've used heavy duty thermostat housing gasket material. I removed the head this past weekend, making sure that I got the threads clean before reinstalling with the thread sealant. Still leaks around the studs. Does anyone have a full proof solution.
Thanks.

[Don Moyer]

Mike,

While I can easily understand the Helicoil leaking (we've pointed out the difficulty we have sealing Helicoils several times in the past) but I don't fully understand why your good efforts have not resulted in sealing of the other stud.

I think we have to assume that the threads in both of your thermostat housing studs are a bit stressed which would explain why a prior rebuilder installed the Helicoil as well as why you're having trouble sealing the other stud. In any case, it's important that we find a solution before having to remove and replace the head many more times. Continued torquing and re-torquing of the rest of the head studs puts you at some risk of other studs weakening as well.

Unfortunately, given your repeated attempts to reseal the Helicoil, I see no way around having to remove the head at least one more time to remove the Helicoil and replacing it with one of our 7/16" repair studs. We can usually remove a Helicoil using an ice pick and needle-nosed pliers. I actually recommend using one of our 7/16" repair studs in the non-Helicoil hole as well.

If after removing the Helicoil, the threads are too large to provide a snug fit on the 7/16" stud, let me know and I'll try to have our shop make a 1/2" repair stud. Again, it's important that this next repair attempt succeeds.

I'll attach an abbreviated instruction sheet with this email. Complete instructions come with each repair stud.

Don

[Chip Hindes]

Don:

Along these same lines, I am in the middle of a rebuild and will be repairing the two thermostat holes as well as another that previously had a Helicoil installed. The two optional repair methods available through your catalog are repair bushings and repair studs. The manual appears to discourage the use of repair studs but that was writtien quite some time ago here you are recommending them.

Is one or the other method preferred and why? Seems to me the repair stud method is a little easier but I don't have a problem with installing the repair bushings if for some reason they are superior.

[Don Moyer]

Chip,I don't believe either method has an advantage over the other in terms of strength. The solid repair bushings have a certain aesthetic advantage for the purists among us, in that they finish off looking and functioning quite like an original block. The difficulty is that they are somewhat more difficult to install while an engine is in the boat and require removal ofthe head. One-piece repair studs install much more easily and can be installed through the head (unless of course a Helicoil is involved).

Don

[Chip Hindes]

OK, thanks. Engine is in all its component parts in my basement, so access is a non issue. I'll go with the busings. Aesthetic reasons are as good as any