have a 360 with a small cam 6 pack heads mopar intake and a holly 4150. will not stay at idle. this is the third carb I have tried and it's the same thing. it will idle at 1100 rpms for about 5 to ten seconds then it climbs to over 2000. I can hold the brake and load the clutch (4-speed)to bring it down but 5 seconds later it climbs.carb has no choke plate and I'm using a stock dist. with over 200,ooo miles. any help would be welcome