I just rebuilt my 305 L69 engine, will be using a CCC quadrajet. I also swapped in a bigger cam (Comp Cams XE268H). I did the 30 minute break in process at 2000-2500rpms and it went fine. When I let off the throttle to idle, it just died. I set the timing to 6 degrees BTDC and same thing it would just die at when I let of the gas. I used the stop screw on the throttle linkage to hold the throttle open just a bit, so it would idle around 700 (I'm pretty sure this isn't the right way to set the idle but it worked for now). I checked the dwell and it was moving between 40 and 45. I was messing with the Idle Air Bleed Valve and the Idle Mixture Screws but the dwell hardly moved. I also checked vacuum and have only about 12" is this a problem?

I'm stumped at what to do next, if anyone could give some advice that would be great!

 

I had the same problem with my L69 with a XE262 cam. My solution was to get rid of the CCC system for a traditional Quadrajet and distributor (though in your case I don't recommend it).

After all my attempts I traced the problem to a faulty computer/sensor that really hated the new cam.

 

Well I got the dwell to read between 25 and 35 degrees. The problem was I used the stop screw on the throttle linkage to keep the throttle open and if I read correctly the idle system works only when the throttle plates are closed. So this is why when I was adjusting the IAB and idle mixture screws the dwell would hardly change because the throttle was slightly open and the idle circuit wasn't in affect.

However now the problem is the car is idling to low (500-600rpm). The only way I know to increase the idle speed is to use that stop screw to hold the throttle plates slightly open. Are there any other ways to increase idle or is this the right way to do it?

I hope what I have said makes sense. I'm kind of new to this stuff and doing my best to learn as I go on, so any help would be great!