Carb Mixture screw

[bobcostas]

Hey dudes.
I've been working a lot on my truck aesthetically. Now I need to get it running tip top. Now that its warm out, it starts up pretty easy, but it still needs a little warm up to get going. I've noticed two things with my 350:

a) my automatic choke is totally boned. it's always pulling down so the choke flapper is vertical. So in other words, no choke.

b) it seems to be running rich. i smell a hint of gas out of the exhaust.

I have a manual choke kit in the mail to fix the auto-choke problem. i like manual anyway, so its a quasi win/win

now i think i have the stock 2 barrel carb on there. do you guys know which screw is the mixture and how much i should mess with it?

thanks a lot. you guys have been a lot of help over the past few months.

[markeb01]

If you can post a photo of the carburetor someone here can probably identify exactly what brand and model you have. Without knowing the specific carb, all I can offer is an old school generic practice.

Obtain a vacuum gauge and connect it to any port with full manifold vacuum. Bring the engine up to normal operating temperature. Assuming there are two idle mixture screws - turn one in slowly until the engine stumbles, then back it out until the highest vacuum reading is obtained. Repeat for the other screw. If it were a one barrel on a six cylinder the same procedure would apply to the single idle mixture screw. This should put you very close to ideal. The next step is drive testing and adjusting both screws in or out no more than a quarter turn at a time for fine tune adjusting.

The other option is to LIGHTLY seat both mixture screws, and then back each screw out the same number of turns, and again check with a vacuum gauge to obtain the highest reading. Some carbs like 1.5 turns out, some like 2.5 turns - it depends on the brand and the model. If the screws are really cranked down to seat them, it will damage the needles and disrupt flow. This is a common problem on old carburetors that have suffered from heavy hands.

[bobcostas]

Thanks Mark!
I'll give it a shot this afternoon.