Did you check any of the work done on the engine? Meaning did you pull any of the pistons, check the fit in the cylinders, push rings down into the cylinders, get them parallel and check ring gap? Have you removed the oil cap to see if there is much blow-by? After the first couple of minutes there should be no blue smoke in an engine that was machined correctly. Will it idle decently? Have you checked with a vacuum gauge? What carburetor and has it been checked recently? If it is a Rochester B and the power piston is stuck it will be running greatly rich (maybe as much as twice too rich) and this won't help anything. Lastly are you using fresh gas or has the gas in the tank been sitting there a while? A couple of months ago I posted 3 images of gas. 2 of them had gone bad in 2 months time (one sitting in a new gas tank on my truck and one sitting in the lawn mower gas can). The bad gas burned more slowly and with notably more smoke and a lot of sticky crud left after it burned, albeit it was black and sooty smoke.
