I’m currently restoring a 1965 Pontiac LeMans/GTO with a (pretty much stock) 326. Among my most annoying and debilitating problems while driving is that the engine has this weird hiccup/buck/seizure problem while I’m stopped at red lights or stop signs. It has gotten to the point that it seizes (rpm drops and engine seems to stop for half a second before picking back up to normal) multiple times before I get going again and occasionally even dies on me!
I’m just learning about all the ins and outs of car restoration and maintenance, but I have recently changed the fuel and air filters, treated the gas for water, cleaned and checked the gaps in the plugs, changed the oil, and set the idle mixture. None of them helped. I have heard that elevation impacts a car and should be adjusted for in the timing (I live at about 4200ft.) My questions are: How much should the timing be adjusted for elevation? Advanced or retarded? And could there be a different cause to these seizures? Thanks!