Carb Adjustments

[Zilverado]

So, after doing my carb rebuild this spring, the truck has never cold-started well. Once warm though, she runs great. I've played with just about every different choke setting (electric) with some success, but nothing too great. I think the fuel mixture and idle need to be tweaked (I never touched them during the rebuild), but I just do not have the time or the expertise to deal with this right now.

So, although I don't like the thought, I have scheduled the truck to go to a mechanic to get it professionally tuned and dialed in on Friday.

So, what are your experiences? Do you find that these adjustments are usually well made by the "profesionals"? The atual manager of the shop admitted that this was definitely a job for the "grey-haired" guys in his shop. As he put it, the ones that know what bias ply tire sizes are...

BTW, this is the same shop that did my front end alignment the other day, and definitely got rid of the annoying pull - she tracks straight as an arrow on the highway now.

Thanks in advance for the feedback.

[Yankeelights]

What kind of carb? If it's a quadrajet I may be able to provide some insight.

~ Dave

[Zilverado]

Yes, it is a Q-jet. Here are a couple of threads I posted during the rebuild...

http://67-72chevytrucks.com/vboard/s...highlight=carb

http://67-72chevytrucks.com/vboard/s...highlight=carb

Like I said, the truck is just a bit of a bear to start initially. Once she's running for 5 minutes, she's great.

I'm sure if I played around with it, I could get it dialed in, but I am VERY short on time these days, and we're going on vacation (using the truck) at the end of next week. So I thought it might be worth an hour or 2 of shop time to have it "professionally" tuned.

What do you think?

[xtreme80]

When you initially start it up in the morning, will it idle higher? If not, try turning your choke until it does. I forget which way, but I think it's counter-clockwise. This opens up the butterfly plate.

Living in Arizona, I have almost no way to adjust the choke to idle higher in the mornings, because it's already almost 90 degrees out in the morning, so I just keep my foot on the pedal for a few minutes to let it warm up.

[Yankeelights]

The first quadrajet that I ever rebuilt started hard. It turns out that the lead plugs were leaking causing the float bowl to empty overnight. I had to crank it like crazy to fill up the float bowl in the morning before she would get any gas. I plugged all 6 of them with JB Weld; problem solved.

Also, my primary throttle shaft was worn badly causing a vaccuum leak. There was not enough vaccuum to allow the choke to operate properly and I had to keep my foot on the gas until she warmed up. I bushed the throttle shaft and everything improved; starting, idle; acceleration and mileage. This was on my 71 C10 with a 66 327 and crane 272 fireball cam. I just did the same quadrajet mods for the 406 that I'm building.

To check the throttle shaft, remove the cables & springs from the carb, crack the throttle a little then wiggle the shaft fore & aft, then up and down. If you can feel any play at all, I would bush the shaft or have it bushed. Hopefully, you won't have to go through this, but it's typical with quadrajets. Here's a couple of good articles with photos that show you how it's done:

http://www.circletrack.com/techartic.../photo_01.html

http://www.chevyhiperformance.com/te...et_carburetor/

Like the guy at the shop told you, if you have them do any of this for you, it's the grey haired guys who can help you out.

~ Dave