So here is the scoop: I am trying to get my freshly rebuilt '51 235 to idle, but I can't seem to get the idle speed below 800 rpm and when I go below that, it runs rough and acts like it wants to cut out. The valve clearances have been triple checked and are correct, the engine is timed slightly advanced, and the idle mixture screw is 1.5 turns out (rochester 1 barrel). I did a vacuum test and at 1000 rpm my gauge is reading 13. So, all signs lead to a vacuum leak. Does this sound right and if so, what's the next step? I have an HEI dizzy with adjustable vacuum advance. Also, I have not done a compression test. Should I do this before I move on? I am noticing a popcorn like sound coming from the manifold side of the motor/carb and there is black soot in the tailpipe. Any advice would be greatly appreciated...
