The old story water in the oil. (This is a 51 L-6). Purchased a head gasket and pulled the head...examining the old gasket wasa inconclusive for a blow out, but when I cleaned up the block I found some rust pitting under the old gasket material. It looks like the water was getting into the valve train through these small pits (it looks like metal after it is rusty slightly bumpy).
So here's the question, what do you recommend for gasket sealer under the gasket to stop the leak?
Speaking of stop leak, the motor is full of it so while I wait for an answer from the group, I'm bottle brushing out the gunked up water passages.
Thanks.

 

I don't know about anyone else but an old way that I have used with very good success is spaying silver paint on both sides of the head gasket before putting it on.

 

you can get some copper coat spray or use the brush on kind works great for pits

 

Spray works good. have used it.

 

permAtex copper coat spray/brush on ..if the surfaces are really bad . a steel brick wrapped in very fine sandpaper.. stuff the cylinder bores with plenty of rags and tape seal them as best you can.. dirty way but i've used it with sucess..or do it right and spend some money and have both the head and the block deck milled .. also be sure the bolt holes are clean and the bolts not hitting junk in the bottom of the threadholes .. dosen't hurt to run a tap down em while the heads off ..

 

Or if you don't feel comfortable with any of the recommendations above you can always use Copper Coat Spray or Brush-on!