Crane Vaccuum advance makes backfire - carb?

Hi all this one has me stymied, and is costing me a load of fuel.

recently, i had to replace a bad distributor. Naturally I removed my Crane Cams 99607-1 before returning the old distributor for a core. I did not remove the advance springs. I did not put new advance springs in the new distributor.

I installed the replacement distributor and hooked up the crane unit. My timing was set to 15* initial.

The car immediately popped and fired through the carb. If the vacuum advance is disconnected, the car runs fine. Although, the mileage is terrible.

Is the crane unit bad?

Any thoughts?

Hey Brian, good to hear from you.

I replaced the distributor because the shaft bushing was shot, back in January. The reluctor was slamming against the pickup.