with the heat crossover welded shut, it makes it hard to idle when the engine is cold. You may need to adjust the choke some more, eg; fast idle cam, opening of choke, rate of opening etc. The heat is there to vaporize some of the mixture and now it is not there. you will need a rich mixture at cold engine temps. Also, chevy trucks are notoriously set up very lean, especially the late 70's early 80'S llike yours. You may also need a higher flowing needle and seat. Rebuilder carbs use generic parts that are barely up to the task on a performance motor. I don't know who rebuilt the carb or what kit was used but most kits today leave a lot to be desired. That is why Cliff is in business and is working around the clock (at least it seems that way..) He has the best kit's on the market and they are reasonably priced. I'd call Cliff to get a kit "tailored" to your specific needs. I think this carb might not be the best choice for your specific combination on the 455 Olds engine. I would look for a 1977 -78 Oldsmobile carb. It would be easier to deal with and get closer to what you need. (JMHO).
