Already done that. Putting it on ported makes no difference and I have already checked my wires and the distributor is brand new from top to bottom and has less then a hundred miles on it. Old carb when it was on did not do this issue at all.
Soon as I put this new one on then it started and that was the only thing I changed. I wanted the electric choke setup of the 80457 so I used the main body and base plate and used my old metering blocks from my 1850 to put on the 80457.
Thing should not have any problems but I have gotten duds out of the box. I bought a brand new holley 670 street avenger almost 5 years ago and the engine would run fine then all of a sudden it would almost die and you would have to keep giving it big shots of gas to keep it running.
Spent countless man hours checking ignition and everything else and ruled out the carb cause it was new. Well after sometime we said it had to be the carb and put my dad's old 80457 carb on he just got rebuilt and it ran just fine.
Replaced my holley 670 with another one and it did the exact same thing like this one cant get rid of an off idle backfire. I sent it back and got a third one and it would not even shot gas out the shooter and taking it apart it looked fine but got fed up with it. Shipped it back then got the 1850 carb and it ran just fine with no issues.
I am going to try a new metering block I got and if that does not get rid of it. I would have kept old carb but I already sold it to help pay for my 80457 carb so to late for that.
I got a spare quick fuel 600 tower to use and if the changing the block does not cure it then I am taking it off and checking it out and if looks anything bad its gone and replaced with the quick fuel one.