just rebuilt 427, new everything, 049 heads, 10.5:1 pistons,had motor built with square port heads, gm L-88 cam factory snowflake 375HP intake, ran at higher rpm, miss at idle. tried everything vaccuum leak test, compression test,two cylinders on passenger side have weak fire when you take wires off makes no change in motor, on drivers side has 1 cylinder same way. tore back down everything looks wonderful built backup with o49 heads lunati solid grind cam with 2500-55oo rpm range and weiland intake and 770 holley carb, everything new changed from mallory dist to chevy hei spark is hot. did the exact same thing ,took it to my buddys big garage with fancy machines, shows everything good except vaccuum is weak on those cylinders, block has never been decked, 3512 block still has factory stamp and vin on the pad.everything checked good at machine shop when machined everything balanced, drives you crazy anybody got any suggestions, somebody told me maybe my cam needs degreed in. thanks

Sounds like a carb or electrical problem to me, I doubt anything is wrong with your motor.

You haved check the resistance through the ignition wires?

Now you'll miss shifting that 427 at 7000+ rpm. Its too much fun!