Quote Originally Posted by JD323 View Post
Adjusting the primary idle mixture screws does absolutely nothing, when screwed all the way in there is no change in how the engine runs, and zero change on the vacuum gauge. When adjusting the secondary screws, it will stall out when they are screwed all the way in, but still virtually no change on the vacuum gauge. Even when adjusting the timing there is no change on the vacuum gauge. I'm using one of the ports in the front bottom of the carb to check vacuum and also run the vacuum advance. I was thinking vacuum leak, but I can't seem to find any anywhere. The fact that the primary idle screw adjustment makes no difference either way makes me think that it's an issue with the carb.
Hi Denny,
Float levels was a good catch, I totally missed it. If the floats are too high it will spill into the carb's venturi and run way rich.

Usually when you can shut the idle mixture off and make no difference it indicates it's getting fuel and air from somewhere else. While a vacuum leak can be a cause, usually it causes a lean condition not rich, this usually leans towards a carburetor issue. High floats or a damaged Power Valve diaphragm or gasket are likely suspects. The vacuum at idle is going to stay low until the overly rich condition is corrected, I suspect a damaged Power Valve issue, and it may be float levels as well.

Mid 90's LT1 usually don't like as much total timing, 32-34° is usually max for their head design.