4.3 backfire
 

I just put a built 4.3 in my s10 the truck is 88 the motor 85 the guy I got the motor from broke it in on a stand so it did run I got it with no carb or dis so I got a eldlebrock 600 and a msd dis complete put it in and got a 3 foot flame just cracking it I've checked timing and all plz help