I have a 1979 Dodge D100 with a 318 4bbl. Just rebuilt factory thermoquad 9223-s. Was using digital timing light to check timing on replacement (not O.E.) distrbutor with pertronix upgrade that has worked great for a while. I noticed that from idle ( factory setting is 8 degrees for my application), the timing will momentarily retard a few degrees before it advances as I open the throttle. This does not happen above idle since either vacuum or cetrifical has begun to engage. I have vacuum and cetrifical advance and verified both are working. Has anyone noticed this phenomenon? I might suspect the timing chain? Its not noticed when driving but does not help for stop light acceleration when looking for max power (think roasting tires ). Does it?? This is more a theory question rather than drivabilty issue. Thanks for the help.

 

Maybe you se the vacuum advance drop out at the hit?????

 

mine would do wacky things like that and when i busted the engine apart, that timing chain had some maaaaajor slack in it. nobody could ever time my car. had to be done by ear.