Yeah like I said in the first post "Cleaned all the mating surfaces impeccably, put a little rtv on the back of the gasket to hold it in place, and then bolted everything back together torquing the manifold in patterned steps." And I did use the RTV for the front and rear gaskets, I've only used the ****ty rubber gaskets once on the first SBC I built and found out they are just good for causing major oil leaks.

When I pulled the lower manifold off again after making the first post there was no signs of water leakage in the gasket area. In fact the little bit of silicone I had put around the ports to hold it in place had squished out into a thin microscopic layer so the manifold apparently seated properly. It's also passed every compression test i've thrown at it. So at this point I've fashened coolant block off plates for the heads so I can pressureize the cooling system with the manifold off and hopefully see where the leak is. I suspect there is a break in the head between the intake port and water jacket but not in the combustion chamber. But that just doesn't seem likely. Now it's just waiting on good weather and days off to line up.

Damn truck, I've got a lot more fun motorcycle projects that it's keeping me from

 

I understand. The reason I mentioned those things are

impeccably can mean diff things to diff people

a "little" rtv on the back - same thing

and

torquing the manifold in patterned steps - maybe you just forgot to check the final torque

So, I only suggested these things because you are apparently having some problems, and problems can often occur by overlooking things - not that you necessarily did though.

I mean, there are only so many ways coolant can get in there, within reason, haha.