It has a 305 with a 4 barrel and its a k10. with a stock electronic ignition, spark plug gap should be 34 or 35 thousandths, any less would start burning the center electrode off the spark plugs, I call the auto parts store they can look this up too !!what should the gap be on my '91 c1500 305. I've tried to research it and couldn't find a thing. 3 Answers. I'm trying to change the spark plugs on my '91 c1500 305 for the first time and im not sure what the gap should be at.
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Remove all the plugs with a plug spanner. With the plugs out, there is no compression in the cylinders, so you can turn the engine easily. Remove the screws or bolts holding the rocker or cam cover to the cylinder head. Carefully lift the cover together with its gasket. Put the cover in a clean place, upside-down on newspaper to catch oil drips.