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Per a previous post, I am re-porcelainizing my intake and exhaust manifolds. Unfortunately, one of the exhaust manifold studs was corroded and broke about 1/2 inch above the flush surface. I used lots of penetrating oil and heat but when I tried to remove it, it broke again about 1/4 inch inside the drilled stud hole. Today, I decided I would have to drill it out, so I started with a very narrow 1/16 bit and to my surprise, it drilled very easily and before I know it I was through the stud, but when I pulled the bit out antifreeze came shooting out through the hole I had drilled through the broken stud! I had noticed that the freeze plugs were located on the same horizontal level as the studs, so I guess it makes sense that the water channels communicate completely with the drilled exhaust stud holes. I've drained the water to a level below the holes, and I suppose I will continue to drill out the broken stud or try an easy out. Does anyone have any experience or words of wisdom with this. I don't think I can do any harm continuing to drill out the broken stud, but I'd appreciate any feedback from anyone who has more knowledge.

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Just realized I forgot to say that this is a 1931 840 engine- thanks!

Just a couple suggestions, reverse drill bit and grease the bit, to help collect the little bits as your drilling.
Wes

Thanks Wesley-- I guess my main question and concern is: Do the exhaust manifold studs normally communicate with the underlying water jackets? If not, I guess it's possible that someone previously drilled too deep and connected with a water jacket. Crack in the block? It's hard to imagine that a bad head gasket could cause this given the location of the stud holes.

Any thoughts?

Those stud holes are all drilled into the water jacket. Carry on. Put some sealer on the new stud.

Thanks Ross- what sealant would be best- I assume a non-hardening sealant would be indicated.

Thanks

In my working life, I had a lot to do with a line of products made in the US by a company called Federal Process. They make an excellent thread sealant called 'Gasoila' soft-set. It is gas and oil compatible, does an excellent job of sealing and never hardens. (so disassembling down the road is never a problem. Just as an aside, this company also makes a 'rust buster' product called 'Free-all' and I have never seen anything that holds a candle to it for breaking loose frozen parts. Check out Gasoila - top-drawer product. Chris

Apologies for jumping in. I've got essentially the same engine and I used Indian Head gasket shellac on my manifold studs, that was nearly 15 years ago and no problems yet.

Many thanks to all who have responded. I'm relieved to hear that these stud holes weren't blind holes but are in contact with the water jacket.

I've never heard of Gasoila products. Looking at their website, they seem to have a sealant for just about every application. They make two gasoline/ethanol resistant types: the Soft Set Thread Paste with PTFE and the E-Seal Thread Sealant. Anyone used both of these- preference?

I suppose Permatex Ultra Black would work well too.

Thanks again!

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If the manifold is a reproduction I would say go ahead and put new porcelain on it, but I would hesitate to do that to an original because I have seen them warp and crack into pieces. So unless the car is a trailer only case there is a very high risk of complications.

The 833 and 840 exhaust manifold are the most robust of the two piece systems, but nobody is deducting anymore for high temperature powder coat so I would do that rather than the porcelain route.