so i belive that my dizzy is bad...it spark knocks bad under med load....gets horrible gas mileage...and the mark on the balancer goes back an forth an dont stay still...it does that with the vac advance on or off...but runs worse with advance connected...

has new plugs wires cap etc etc

now heres the thing...my motor is from a 72?...my trucks an 86...when i bought the dizzy it asked for with or without vacc advance....but the 72 motor also said same...

so will this vac advance work with my truck?

 

The truck must have a vacuum advance. The same distributor is used in both years. The parts store is telling you that they offer the distributor with or without a vacuum advance because the vacuum advance can be purchased separately.

 

ah gotca/...thanks for the help