If you can find it, Sodium Silicate works especially well. I used to find it in the drug store. It is also known as Iron Glass.
Plug off all of the water jacket holes. I used to use a piece of flat steel for the block to head surface. Place the sealed up head in an oven and heat it up to about 275 degrees. let is stay in there for a couple of hours to insure that it is evenly heated all the way through.
Mix up the Sodium Silicate if needed. It usually comes in a liquid form in a glass jar.
Remove the head from the oven. You'll need a pair of oven mitts or something comparable. Pour the liquid into the head through the thermostat housing hole and plug it up. Slosh the liquid around in the head until it no longer shows any leaks and dump out the excess liquid.
I've used this stuff numerous times on leaky, porous heads and blocks. It works well and doesn't effect cooling. DO NOT let it stay in the head!!! Pour out the excess as soon as evidence of leakage has stopped!! It can harden in block passages that you can't clean out.
I learned this trick from Smokey Yunick. Again! It has always worked for me.
Last edited by Blackwater; 06/18/16 04:26 PM.
