carb running too rich!

Placing too small a carburetor on an engine will generally cause an overrich condition (up to the point where the engine runs out of air); as the velocity of air in the larger engine pulls more fuel out of the fuel wells. Conversely, placing too large a carburetor on an engine can cause a lean condition.

Easiest fix is obtain the correct carburetor; however, anytime there is a perceived problem with the carburetor always check the ignition first.

Jon.

Thanx for the response,CarbKing.In this aplication the carb used on the 317ci and the 389ci is the same cfm carter wcfb,the only diference to my knowledge is the diferent size jets,should I just be looking for bigger jets?or Is the float level responsible?its a freshley professionally rebuilt carb.thanx so much!

vepf - the WCFB used on the 317 is significantly smaller than the factory 4-barrels used on the 389. Here is a link of original carburetors used by Pontiac up through the 1960 model year:

Pontiac carbs 1926~1960

And 1961~1967

Pontiac carbs 1961~1967

Jon.