Vacuum Advance
Posted: Thu Feb 18, 2016 11:49 pm
Hello--I hope everyone is well--I'd like to see some discussion of vacuum advance...in particular, how it needs to be used on a 144 six. My car has a Holley 1940 1V that was a dealer replacement for the original carb. However, it does not have the spark control valve. When I check the timing, it advances as the rpm's increase, as I think the vacuum is coming from above the throttle plate. However, there is no advance at idle, and spark does not retard when the throttle is opened quickly (load on engine). What should the advance characteristics look like? Should vacuum be acting on the dist. while at idle? Should spark retard when throttle is suddenly opened? I've read so much online which is contradictory. Some say vacuum from the manifold is the way to go, but wouldn't that advance the spark way too far at idle? Right now the engine idles smoothly at about 8-10 BTDC, and does not knock when accelerating, but am I missing some performance? I can't tell since the motor is so puny to begin with! Thanks