I've tried everything I know from timing, points,plugs and carb adjustments and once the car gets up to running temperature it spark knocks on acceleration. I cannot get rid of it. I've tried all grades of fuel from low grade to even adding Cam 2. I'm also hearing what appears to be a back fire through the exhaust as well. I checked the vacuum adavnce with a gauge and it appeared to work fine,held vacuum. I re torqued all the manifold bolts. I'm very frustrated at this point. Could there be a bad vacuum hose or maybe the vacuum tree fitting on the thermostat housing is bad. How do I test that?....Could a bent rod cause this...help....