Hey ThreeTree,
I am a rookie here and would not usually have anything to offer - except that a similar pattern just happened with me. 1950 GMC 1/2 ton with 216. Ran the best it ever did - took her for a "big" 50 mi trip smiling all the way. Then a week later very hard to start, ran really rough & needed high RPM just to keep ticking. Compression test on #5 cylinder was zero - ended up being a broken intake valve spring. Plug on that cylinder was really dry sooty.
Hope for your sake it is something better - but worth checking the compression.
G' luck
Jim
Last edited by GMJim; 06/15/2021 10:50 PM.
