You might also want to check the mechanical distributor advance mechanism?

If it has been sitting for a long time, grime and grunge may be causing them to stick and operate erratically (if at all).

~ Dan
1951 Chevy 3 window 3100
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"My Grandpa Carl's Truck and How it Became Mine"
1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver)
US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)