I have a 350 with a 750 vac sec. I've always had the idle screw backed out to far to get the rpm's down to 800. It has a TA dual plane with a adaptor plate with two gaskets to run the 4150. It does have a PVC provision on the carb and it is hooked up to the manifold with a pvc valve. When i block it off it doesn't drop much rpm. Both pri and sec plate are closed in the bore and it still idles at 650. 4 corners are 1/2 turn out. all jets and bleeds are spec. so where is the leak coming from and how to find it. a few months ago i tried a new gasket with no results. thanks!
today i plugged the brake booster tap on the manifold and made sure the other tap was sealed good. I put a cap on the PVC tube on the carb and made sure the vacuum sources were plugged. I got a can of carb cleaner and went looking for a leak around the base of the carb and along the sides of the manifold. Then i tried starting fluid, no luck. I didn't find anything, i did check that the idle did dip when spraying a bit into the carb. 20* of timing, both plates bottomed out. does that mean it has to leak under the manifold? BTW, car runs really good at idle and off idle.
