ok so nothing new to some but could have saved me MONTHS of frustration had i known this: and i quote: .......Nailhead distributors differed in the amount of mechanical advance built into them depending on the year of the engine and other options........ That could be it! The '63 LeSabre 401 with Dynaflow automatic trans is spec'd at 12* BTDC. The later 64-up with ST400 automatic is spec'd at 2.5* BTDC. thanks to all (esp wkillgs) in my thread on overheating and using an IR gun here: http://www.v8buick.com/showthread.php?314362-what-is-normal-head-temp-with-IR-gun
