Exhaust port crack.... need help!

[Matts30coupe]

So I found my culprit that has been feeding my exhaust antifreeze... I took down my model "B" block today to find an old repair. Someone stitched the crack and them threw a weld over the top. The stitch was not overlapped and was never properly sealed. So with what I had here in the garage, I tried to preheat, braze, and postheat only to find more cracks... I was able to cover most of the cracks and smooth it out with a bur-bit, but I am not totally confident with the fix...

Does anyone out there know of a product that I can use to coat over the top of this. (Epoxy/Sealer???) They are hairline cracks that don't deal with a lot of pressure, I just want to run this motor till I upgrade to something later down the road.

***** I can't stitch where all of the cracks are.. so if it can't be brazed, I'm wondering if a epoxy or sealer will hold up to the temp.

Anyone have luck with this, or can recommend a product??

Thanks,
Matt