The Stovebolt Site Forums The Shop Area Engine Shop Stock 305E carb adjustment(s)

OK...First the story: picked up a 1965 GMC 1/2T with the original 305E, original carb and air cleaner, 4 speed manual, original GMC AM radio, and faded with a little surface rust but original paint. I moved it from Sacramento, Ca to Reno, Nevada. Reno is about 4500 AMSL and Sac-town is about 100 AMSL. After replacing the starter and getting a new battery, she fired right up!!! Put the plates on 'er and went into town. Truck ran great down the freeway but upon exiting it died on the on ramp. It kept on dying on me and running rough at idle. I have to pull the choke out a bit to keep it running at idle. I saw the idle speed adjustment, but am wondering if there are other adjustments to make i.e. idle mixture and what is the proper procedure. I'm getting little backfires outa the exhaust, and it smells like it's running too rich.

Any reply is greatly appreciated. This is my first GMC and I'm enjoying it so far.

Scott :confused: :confused:

I've made the same trip up to Reno and back and know what your talking about.

With the engine running and at idle turn the mixture screw in until the idle slows down and then back out until you get the best idle speed.

You probably want to check the fuel filter and also check your points because I think that's where your popping is coming from.

Thanks for the reply Joe. Now the newbie question: Where is the idle mixture adjustment??

:rolleyes:

what kind of carburator are you running on it? if your facing the engine, the mixture screw will be on the left side on a carter, same for the rochester M carb, on the backside of the carb for a rochester 2G carb, and if its a Bendix stromburg, they will be on the front of the carb.

In order to adjust the mixture on your carb, it probably a good idea that you check a few things. This depends on your carburator.you have to make sure the timing is correct, check vaccum, RPM and other things in order to set the mixture. I would find a Chilton manual on trucks from 1961 to 71. I have this book, and it tells you the procedures for adjusting the carbs on all V6 GMC engines.

I hope I didnt confuse you with all this carb stuff, but I hope this helps anyway. some one else can probably help you out more with Mixture and stuff, so make sure you read up on procedures and stuff before adjusting your carb.

[ 11-10-2001: Message edited by: gmcfan ]

Thanks for the help. Carb turns out to be a Stromberg (idle mixture screws on front part of carb). Checked the timing, checked for vacume leaks, and then set the idle mixtures. Truck runs great!!! Starts right up!! Now all I hafta do is the brakes and drivers side glass and I'm in "tall cotton"!! Thanks again