I RAN A 500CFM PERFORMER ON MY 304, CHANGED IT TO A Q-JET THOUGHT I NEEDED BIGGER .........UH??? THE CARB WAS OFF A 77 CHEVY TRUCK THAT HAD SAT FOR A COUPLE YEARS BOLTED IT ON WITH THAT ADAPTER AND HAD NO PROBLEMS, BUT I AM ALSO RUNNING A T 18. THE BIG SECONDARIES ARE NICE, REALLY OPENED IT UP WHEN YOU PUNCHED ON IT. CHANGED TO A 1405 600 CFM PERFORMER CARB WHEN I REBUILT THE ENGINE, NOT MUCH DIFF. THE Q-JET MAY HAVE HAD ALITTLE MORE UMF WHEN YOU PUNCH IT. BUT I TINKERED WITH THE QJET ALOT. STILL TRYING TO DIAL IN THE 1405 TO FIND THE BEST A/F SEEMS LIKE I CAN'T GET IT RICH ENOUGH. THERE IS A SMALL HICK UP OR BOG WHEN COLD AND YOU PUNCH IT ,BUT THAT HAS ALWAYS BEEN THERE NO MATTER WHAT CARB AND BEFORE OR AFTER THE REBUILD?? STILL FIGURING IT OUT. WITH TRHE 1405 AND THE RICHEST JETS IN THE KIT IT HAS GONE AWAY. STILL HAPPENED, BUT ONLY A FEW TIMES.