Put a carburetor kit in this 345 that has a history of idling on 4 cylinders. It runs better now, but still not firing an all 8 cylinders just above idle speed. Actually it probably does't do this "untill" you give it a slight throttle advance - Then you can here it labor on only 4 cylinders for a little bit, and after that, if you give it more throttle it will clear up and pull like a champ. The motor is in a 1966 1800 Loadstar farm truck. This thing has had a history of this for all it's life. ( 35 years) This most recent carb. tear down showed very little contamination any where. With the exception of a lot of black from the backfiring it goes threw when you advance the throttle. It is running a 2300 Holley with a governor set-up from the factory. Allen E., You told me to check the cylinders and find out which ones where not firing during this. It's the center two( 3 & 5 which I pulled ) and the # 2 and 8. Could this be any vacuum leak that is isolated to only that side of the intake? That would effect the idle though wouldn't it ? The low end Idle screws seem to be effective, and it runs smooth at absolute idle. At tear down I checked the throttle openings at idle and they seem to be synchronized with each other. I'm very puzzled at this time. Could anybody come up with some advice as to where I go from this point ? ? Thanks in advance to all the I H Minds I read at this site!