ABC's of Carburetion



	THE CARBURETOR'S JOB Continued



	SPARK TIMING

	There is one more job the carburetor does, though somewhat indirectly. In most modern cars, the carburetor bore just above the throttle valve is the location of a vacuum port leading to the automatic spark advance on the distributor. This automatic advance is cali-	brated to regulate the spark timing correctly for satisfactory operation under various loads. Manifold vacuum is the factor most sensitive to loads; the vacuum port in the carburetor is the means by which timing is made to vary with manifold vacuum and thus engine loads.

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