Quote:
Originally Posted by Classics Fan
Yeah, Quadrajet. I’ve only tuned an idle circuit once, on a 72 Pontiac 350, but did it in Park. Why Drive? I wasn’t planning on tuning this one since I know it’s pulling 15” vacuum at idle, and there’s virtually no exhaust smell in the shop when the door is shut and the truck’s running. I’m a novice at tuning but am finding it enjoyable. Just ordered a Moroso kit, should see it before the end of the week.
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So just a little 101 on tuning:
First for your carb you want to make sure the idle set screw is set so that your transfer slots look like squares when viewed from the underside. If you've played with this screw to set your idle speed you may induce an off idle stumble if the transfer slots are overexposed.
Then set your initial timing to achieve the idle rpm you want. Larger cams will need more initial.
Then you set your idle mixture screws in drive simply because that's where you need the right mix, in drive ready to drive the car, with a load on the engine from the torque converter.
Then set your idle mixture screws for best/highest vacuum.
All of this has less to do with exhaust smell and more with optimizing the AFR at idle and this is how you do that short of an AFR gauge.You may very well have the right tune on your carb/distributor but this is how you do it from square 1.