Engine Dieseling - Options?

I was able to do a little check tonight - got the engine warm and checked for vacuum leaks - nothing shows up any where - good and bad I guess but will eliminate that as an issue - next I backed everything off on the carb, mixture screws front to 3/4 and rears to a 1/4, idle screw backed off completely, reset timing to 20 - idle down to around 900, vacuum now moving between 7 and 9, not jumpy or fluttering though. heavy rpm drop when going into gear, exhaust smells a little rich still - dieseling was nearly gone, cranking still ok with no kickback. Looks like I will find a decent spot for initial from 16 to 20, so looks like Im heading in the right direction, I would be OK driving as is to go top off the gas tank and finish diluting the octane boost juice down. starting to hope again I can tune out and run on pump gas - Im gonna get back at it this weekend, first thing is the carb is coming off for a good thorough inspection if I can get a rebuild kit with all the gaskets, may even re-jet my 670 and put in on there - it has been a proven performer on my Mustang - thanks for all the info - will see what I can do with a little refresh of thinking


When you get it right, the RPM drop should be no more than 150 RPM from neutral to in gear.

Usually when you see a big drop like that, the curve in the distributor is wrong. Once you clean that up, you’ll probably have to take some fuel away at idle.