Re: 302 rough idle, hesitation, backfire through carb.
I thank all of you for your input! I tried everything you all suggested, and I believe we found the problem. We found the engine was misfiring but only above an idle. We isolated the misfire to one cylinder, (no. 3), and identified the intake valve spring as being weak. I just had the heads serviced and am very upset that they did not check the springs, since this whole mess would have been averted. We are going to replace the one spring on Monday, and with any luck I will be up and running again!
302 with Edelbrock performer 600 cfm carb., performer cam, and permormer intake.