Zph , If your engine is running alright and you warm it up dont worry about thining the oil, but you do need to take care this . I dont mean to deminish your concern just dont pannic. Hear is what you do. remove the air cleaner cover and start the engine and warm it up . Now with the warmed engine that has the timing set and new or good NGK spark plugs, with the engine at idle incert your finger into the rear carberater's throat and lift the slide about 1 inch. this will disable the carb. and the engine will be running only on the front one . The engine should stumble and run roughly but not quite die , if it dies your too lean, if it runs and doesn't run vary rough , you are rich. To lean out the carb. reach under the carb and feel the large knob like fitting that has sirrations on it , this is the adjustment "knob" . To lean it crg turn counter clock wise or as if you were tightening it. give it a half a turn. and re test. when you get the front one adjusted do the same with the rear one. They must be ballanced for air flow before all this is done . There is a devise that makes ballancing the carbs easy , it a Uni-Syn mine came from edelbroock and I got it at the local parts store in there speed shop area. Now to varify weather you have set the carbs mixture correctly drive the car for a few miles and then pull a couple of pluggs and see how they look . I usually pull 1 an 3 4 an6 this way you are checking both carbs . Once you have done all of this you will see that it is not all that hard or complicated . Good luck to ya, Gary Portland Ore