Hey guys, thought I would ask you all to see if someone can help me fix a problem. So I had a Holley 3310-S carb, which is a 750 cfm with a vacuum secondary. Years back I changed out the main body to a Proform brand one and also changed out secondary metering plate to metering block. It ran perfectly on my hopped up 355 SBC back then with no jetting or other changes. After that I had it on my SS for years and it performed flawlessly. I switched to a SMI 850 DP after I upgraded my 406 and needed more fuel. My buddy bought the carb off of me to put on his 406 SBC S-10. Earlier this year the baseplate cracked. So we put on a Proform billet baseplate and have been having major issues ever since. First of all, the mixtures screws used to be 1 to 1 1/2 turns out now they have to be 3 1/2 turns out to keep it running and when revved it returns to idle very slowly.If you stick a paper clip down both idle air bleeds it picks up rpm at idle. This to me indicates there is a vacuum leak somewhere, but I have sprayed all around the carb with carb cleaner with no rpm change. Secondly, at 6000 rpm exactly the motor just lays down. We have checked to make sure it isn't valve float by changing to a 770 Street Avenger carb another buddy had. Engine is way more responsive and feels like you just picked up 50hp and revs beyond 6000 rpm easily. I have disassembled the carb a number of times and the only thing I could find was one screw hole on the quick change vacuum secondary pod had stripped out and was causing a leak, so I changed the pod. Helped it out a little bit, but there is still a major issue somewhere. I have cleaned all passages and such checking for obstructions...found nothing. I have used new gaskets in it and also new carb to intake gasket. I don't know what else to look for and check. Any suggestions guys?
