This past weekend I started trying out my new Craftsman Advance timing light, the kind where you can dial in your advance on the light. I discovered that my ZZ4 distributor wouldn't allow more than 28 degrees mechanical advance, when starting at 12 degrees initial. I tried everything, finally Lars suggested I try 16-18 initial advance for a total of 32-34 mechanical advance. I tried this and the car performed good enough, but I had a problem with popping under light loads (high vacuum, bringing in the vacuum advance.)
I finally pulled the weights and plate off the distributor and tried to find out why it wasn't advancing enough. There had been some slight binding that I noticed when I tried manipulated the advance mechanism before I removed the center plate. After I put everything back in place the advance seemed to work a lot smoother while I was manipulating it.
I fired the car back up and set the initial timing back to 12 degrees, then I reved the engine to 3000 and I had 34 degrees timing! Then I hooked up the vacuum advance and had a total of 52 degrees. I took the car out and it ran like a spotted a-s-s-e-d ape. The off idle throttle response was spectacular, no surge, no bog just roar! It still runs out of gas about 4500 due to the small carb that I have on the engine, but I'm working on that problem.
So you guys check your stock HEI distributors and make sure that you're getting all the advance you need.

 

After using your new engine for awhile, try checking the inside of your rotor cap. You should see where the centrifugal weights contact the rotor. The rotor acts like a mechanical advance stop. Sometimes the weights flop under the "stop" and can give you too much advance. Just another weird thing that I've experienced w/HEIs.

Enjoy the power!

 

If you're running a 650 cfm carb you shouldn't be "running out of gas" at 4500 (or at 5500). What does it do at 4500? Does it just quit making power? Any sounds? Bucking? Anything?

 

I'm not using the 650 at this time. My Q-jet is junk, I have a Holley "Economaster" Q-Jet replacement, it's only about 425-475 cfm, it is a great carb for cruisin' and good mileage, but not much else. I'm having trouble finding an air cleaner that will fit over the Holley 4011 double-pumper, due to the wierd way the fuel lines go into the sides of the carb.
Besides I'm trying to "break-in" the ZZ-4, having a small carb will make me less likely to accept the numerous challenges I get from 5.0 'rustangs and ricers. :D Knowing that it is going to give up the ghost about 4500, keeps me from abusing it until I get a few more miles on it. I'm getting close to 1000 miles on the engine, so I'm really looking for a way to use that 4011 before too long.