when you change the timing chain in a chevy you are setting the valve timing. if you took the distributor out you have to set the ignition timing by finding no.1 tdc ON COMPRESSION NOT EXHAUST. because the valve timing is different it is set at no.6 tdc on v8 engines. if you set it as it sits on valve timing it will be off and low on power. it took me a month to figure this out now my van turns 1/2 of a turn and fires right up and runs smoothly and as soon as I get my fuel tank cleared up it will be back on the road.