What are the symptoms if the carburetor is too big for the engine. I had a stock 1970 Q-jet (750CFM) poop out on my brothers daily driver (Skylark w/350). I stuck the Q-jet from my Riv (800CFM) on it for the time being. I adjusted the idle speed screw all the way down and it still idles too high. I assume this means the carb is just way too much. I do get a response from the idle mixture screws i.e. the idle drops way down when I turn one of the screws in. The car dies if I turn both of them in. Also, on both of the carburetors (750 and 800) when I pull off a manifold vaccum hose the idle increases instead of decreasing? What does this tell me, if anything? My brother is probably going to buy a new carb. Should I reccommend that he stick with 750cfm, or should he go smaller?
First thing is to check for vacuim leaks. Most of the time a high idle is a leak. If everything is sealed up then check to see if the secondary throttle plates are stuck open a little. This will also keep the idle up. Good luck Mike
is the choke still on one of the steps of the fast idle cam, you may have to back the screw on the passengers side down to get the throttle to close properly, if everythings o.k., look down the primaries while the car is idling, (use safety glasses!), if there is gas dripping out of the main nozzle while the car is idling, something is wrong (high float, dirt in needle, too much fuel pressure). if there is no gas dripping, adjust screws accordingly, speed screw (drivers side near linkage) 1/2 turn in after making contact with linkage. mixture screws start at 3 1/2 turns out, then gradually turn one at a time until rpm drops, once rpm drop turn respective screw out until rpm recovers, this may require a few tries. make sure the distributor vacumn line is disconnected and plugged while making adjustments, and all other vacumn lines are connected or plugged. good luck
