I have a 454 with a fairly strong street cam and yesterday I went to go out and the car really idled very rich. Came back home and the secondary carb. float was too high (Demon Carb). I lowered the float level and went back down the street. The car seemed to run good but when I let off the gas it would slightly pop (backfire). The timing was checked and it right where its always been. Is it possible that I fouled the spark plugs causing some slight back poping? Open for suggestions!!!!!

I am guessing that you are still too rich on decel and you have gas igniting in your exhaust system. Need to get things a bit leaner methinks

A fouled plud plug is a very possible cause. Please don't take offense but I gotta ask: If you think you have a fouled plug, why are you asking us instead of checking your plugs?

A fouled plug is a "symptom" not a "cause" of a problem.In other words something caused that plug to foul, you need to find out what and then no more fouled plugs.

I got home too late last night to change them but not to late to check w/ team Chevelle via this site.

I'd also check for an exhaust leak at the headers that are feeding air into your exhaust, typical of backfiring when you let off the gas.

High fuel pressure will make engine idle rich. I have a demon 825 the needle and seats that come with carb were junk and I found a piece of bronze metal shaving in between needle and seat causing high float levls and flooding. I replaced neddle and seats with Holley .130 seats float levels set to the second line in sight glass. No more rich idle and flooding of carb and fouled out plugs. I did not get any back fire tho. If raw gas gets in the exhaust it will pop and will see black run off on exhaust connections. By the way I took my carb apart and cleaned out many metal shavings and put in all new gaskets I used BG carb kit. Comes with all needed to freshen up. Hope it helps out.