Try some PB Blaster on the valve stems to start with. then after running a while I would hope they begin to free up and all is well.

Did you use SAE 30 weight oil?
Not sure what you should use, but that's what I used. Non detergent if an old engine that probably had it to start with, and normal detergent if rebuilt or known to be clean from the start.

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-