What is the cfm rating on a stock carburetor 1986 gmc sierra pickup with 305?

There isn't a single CFM rating for a stock 1986 GMC Sierra 1500 with a 305 engine. The carburetor's CFM (cubic feet per minute) rating depends on several factors, including the specific model of carburetor used and even minor variations in manufacturing. GM used different Rochester Quadrajet and sometimes even Motorcraft carburetors across their various trim levels and options for that year and engine.

To find the CFM rating, you'd need to:

1. Identify the carburetor: Look at the carburetor itself for casting numbers. This will allow you to look up the specifications online, through parts catalogs (like those from GM), or with the help of a mechanic familiar with these engines.

2. Consult a parts catalog or service manual: Once you have the carburetor's identification number, you can often find its specifications, including the CFM rating, in a GM parts catalog or a repair manual specific to your 1986 GMC Sierra with the 305 engine.

Without the carburetor's identification, it's impossible to give you a precise CFM rating. A general guess for a stock 305 in that year might be in the 500-600 CFM range, but this is just an approximation, and it could easily be higher or lower depending on the specific carburetor fitted.