Pin hole in cast iron head

Earlie A said
Your math is spot on. I also think you are correct in the hole size guess. My concern with the epoxy is the long term. The force pushing on the epoxy would be 0.005 lbf if the epoxy stayed 100% adhered to the cast iron. If the epoxy lost contact with the cast iron, the 16 psi would be acting on a larger area. It is then a snowball until failure.

I like the thought of brazing/soldering but brazing especially would require high localized heat on a thin metal area. I have a buddy that's a great mechanic and fabricator, but even he is not that comfortable with cast iron.

I'm thinking of drilling a small diameter exploratory hole (in the existing hole) to try to decide if there is enough metal to tap/plug or braze. Seems like even brazing would want fresh metal.

Other thoughts - how big of a hole would radiator leak stop fix?

And it is a leak because my colored alcohol (that I use for cc'ing) slowly trickled from the port side into the water jacket.

There are several issues you will deal with.

One is cast iron. It’s problematic in its own right.

And then to that add all the scale and **** that is on that old cast iron. Even if you shot blast the head you will still deal with the remnants of that crap. Cast iron is dirty on its own. Used cast iron is nasty.

If that head was aluminum I would go in there with a grinder and clean out the area so I could get to the other side of the casting.

Then I’d weld it around, in and then out.

The biggest issue you’ll find is how thin the entire area is. You have to control the heat while still getting a clean weld.

You might get lucky if you can screw a pin into the hole and then weld the pin in place but that still takes heat.

You are between a rock and a hard place.

IMO I wouldn’t spend a second messing with it. You lose all your work BUT if you try and repair it and it fails you are out all that work too.