Engine now smoking after new valve seals

Professor Fate said
So, what has changed between then and now?
You had the heads off, and put the heads back on.

Blue smoke or white/gray steam?
My guess? Head gasket(s).
Run a compression test, and pressurize the cooling system to see if you can confirm the leak before you tear it all down again.
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Nothing has changed other than the valve seal bosses were cut lower and narrower then new seals installed by a machine shop and built back up by them.

White/grey smoke out the tailpipes, pretty thick smoke too. Definitely doesn’t seem like steam.