nor am I trying to imply that your not inteligent, it's just that we can all make a mistake now and again, or get sidetracked or distractracted.
IF all else fails, go back to the basics, is the point gap correct? are the valves properly adjusted? is the timing at the correct setting? ETC.
I have, over the years seen where valves are ourt of adjustment, and they will be tight, as in keeping some or all of the valves partially open. intake valves are prone to do this on A series engines and the exhaust valves will be loose.
all any of us are trying to do is offer suggestions that might help, please don't take it personal.