180-Degree Distributor Indexing Error

A 180-degree indexing error occurs when the distributor is installed with the rotor pointing toward the cylinder #1 terminal while the engine is on the exhaust stroke rather than the compression stroke. Because the four-stroke cycle requires the spark to occur only during the compression stroke, the engine will fail to hold idle or take revs, often accompanied by backfiring through the carburetor or exhaust. This is confirmed by verifying that the cam lobes for cylinder #1 are pointing toward each other (exhaust stroke) when the crankshaft 'P' mark is aligned at Top Dead Center (TDC).