Idle problem

It has PCV valve. The power valve is stock, I believe it's 6.5. I haven't adjusted secondary butterfies. The higher the idle, the better the idle. When I put timing light on it and adjust for around 12 degrees initial, it won't run. That's why I just adjust distrib. until it runs OK. Car has plenty of power and starts well. I did check damper for correct zero against timing mark with TDC tool, it was right on. When I first built engine I had a 750 Edelbrock on it and I had the same problem where it would start shaking. I thought it was defective and replaced it with Holley. My opinion is that the transfer slot has too much showing and like you Guys said, I should adjust secondaries or drill holes in primary butterfies. I guess I'm trying to rule out other options before I try messing with the carb. Gauge is stock gauge in 66 Barracuda. I did try another gauge hooked to vacuum port of carb.