I agree with the others, this is a simple valve lash adjustment.
Funny how many 'modern' mechanic's assume things about these old cars that they know nothing about. I had one tell me once that there was no way my 273 came stock with mechanical solid lifter cam and that ALL dodge small blocks were hydraulic. Same genius also told me they didnt make forged cranks for small blocks. Ah well.
Motor's manuals are a great reference, but are harder to find. I got mine some years back from an old amish guy. Waterdamaged, but I carefully opened & separated the pages for Dodge and Plymouth.
