Unanswered Carb Adjustment Question

[braol]

So, things are going great with the new-to-me '31 Tudor. It starts, runs , and drives quite well and we have gone out in it almost every other day..to the store, local tavern, restaurants, etc... But here's what I have noticed:


Car starts fine on one full turn of the GAV. Advance the spark and the engine runs faster and smooths out. Wait for it to warm up for a bit and then when I close the GAV valve engine RPM slowly climbs until I'm at about only 1/4 turn open at idle. SO far so good...this mimics the instructions in the owner's manual. The issue is while driving. I find that while driving I only get good power with about 3 to 4 full turns of the GAV valve...any less and I get low power and even the occasional backfire under full throttle. Please note that I have sprayed WD-40 around the intake manifold and carb to see if I might have an air leak of some sort...to no avail.


I read that any more than one full turn of the GAV should make no difference, but that is not the case in my situation. I can start, run, and drive all day long with 3-4 full turns of the GAV valve but I get higher RPM (the "sweet spot") at idle with the GAV valve at the recommended 1/2-to-1/4 turn open. What gives?


My instinct tells me this: With the throttle closed the idle system is performing as it should. With the throttle open/accelerating I am lean...so there must be a "main jet" that is perhaps clogged? What puzzles me is that the GAV valve is supposed to have no effect beyond 1 full turn (or so) opened...yet is DOES obviously affect the mixture with the throttle opened up. Please help.