Unusual Backfiring Problems

i have a 64 polara 440 auto . this 440 had a 750 cfm eldelbrock on it and it would run okay as long as u were not on it ! as soon as u floored it after 3 grand it would miss fire like crazy :banghead: so my engine biulder tells me its ignition :protest: not have all new electronic !! put a rebuilt 750 holley on it no miss fire pulls like crazy :burnout:just a thought might be the eldelbrock


mike