Hey guys, needing some help as I'm currently stumped and I know talking with you all, someone will have the right answer for me. Well I know this isn't in my SS, but thought I could find help here anyways. In my 1989 Chevy K1500 I pulled out the TBI engine and I have installed a 406 SBC with TrickFlow heads, Comp XE274 cam, RPM Airgap intake and a Eddy 750 carb. The problem I am having is after a year of having this thing together it just started backfiring through the carb under hard acceleration. I had previously jetted down the carb on the primary and secondary for better fuel economy with no issues and ran it this way for 9 months. Checked plugs and they were all clean white with little tan, so I jetted up all back to stock and even went a few stages past on the rich side with no change. I also upped the step-up spring from 5" to 7" to get it to go to the power mode a little quicker with no change. When it backfires it is a repeated backfire under WOT but if I lightly and quickly flutter the gas pedal from floored to just a little less it is fine. I'm going to change the carb to intake gasket to see if there is a leak there, also check fuel pressure to see if pump is weak. Also thinking of changing the pick-up coil, but with the fluttering of the pedal kinda getting it to not backfire I don't think the pick-up coil is the problem. Any other suggestions guys would be greatly appreciated. Thanks
