I've also been using calyx for several decades and can attest to its effectiveness on cast iron manifolds. It also does a good job on cast iron master cylinders. Apply it with a toothbrush
Regarding exhaust manifold treatment:
Somthing I’m trying on a non-Stovebolt engine in my life….graphite spray line. I don’t recall where I got the idea (probably YouTube). It’s cheap, available at any hardware store, and easy to touch up.
I can’t report any results just yet as this engine has yet to fire. But in raw form I think it looks really good.
