My truck is a 1986 C10 2wd, Auto, 305, 700R4, Rochester QuadraJet Carb, Headers, Dual Exhaust. I`m not sure what ports those plugged lines went to. Some of the lines were plugged already by the previous owner. I would prefer to get all original lines connected as much as possible. So now I am in the process of putting things back together. I did'nt mark my vacuum lines when I did the Head Gaskets Having said that, the numbers I shared may be a good starting point.Īdding an affordable vacuum gauge to your toolbox is a good idea, but you can tune your Quadrajet carburetor pretty well without one, provided the carb and the engine are in proper running condition.So let's start by being Honest. Every situation is different, so my advice is to educate yourself as much as possible on the subject. Now, the adjustments that worked for me may not work for your carburetor. And you certainly don't need to buy a new carburetor. You do not need to spend money (sometimes lots of it) with a mechanic. if you do a little bit of research and follow standard procedures, your car will idle and operate properly. Frankly, I want to adjust it to the best of my ability. My plan is to drive the car like this for a few days and then I will use the vacuum gauge to fine-tune the carb since I cannot leave well-enough alone. But I had to experiment some more, so I adjusted the idle mixture screws one more time to 1¼ turns.Īfter another long test drive it seems that's the magic number. The engine is running smoothly and is very responsive, and there's hardly any gasoline odor either while driving or after I pull into the garage. I drove the car again the next day for about an hour. So I reset the mixture screws and went with 1½ turns from fully seated for each side. When I pulled back into the garage I shut the engine off and restarted it a couple of times without any issues, other than I felt it was still running a bit rich. Late that evening I took the car out for a long drive, and it ran better than ever. It started right up and idled so smooth it surprised me. Honestly, I thought it was going to be hard to start and/or idle poorly.
#1977 el camino emission vacuum with quadrajet full#
I started with the lowest digit and I turned each screw two full turns out. Like I said before, the suggested number of turns ranges from two full turns counterclockwise to four-and-a-half. You must establish a starting point and start counting from there. Your starting point may be at 2-o-clock or elsewhere, but the same principle applies. Remember, both idle mixture screws must be adjusted equally!Īnd don't expect your carburetor's idle mixture screws to be exactly as shown in the diagram. I don't want to state the obvious but it is important to know what a quarter-turn, a half-turn, three-quarter-turn, and a full-turn are. Once they are fully seated, start turning them counterclockwise (to the left) counting each full turn. Once the car is at normal operating temperature, shut it off and turn the idle mixture screws until they're fully seated by turning them clockwise.Īlso, make sure you count the exact number of turns for each side, and you may want to write those numbers down just in case you need to reset your carburetor to the previous setting. It is important to note that "fully seated" means snug but lightly. I decided to give this approach a try to see if it would solve my idle issues.
I watched a whole bunch of how-to tuning videos and the takeaway was to set the mixture screws anywhere from two to four-and-a-half turns out (from fully-seated). I was on the right path but putting the cart in front of the horse. Using my misguided approach, I ended up running from one side of the car to the other like a madman, losing track of how much I had turned the previous mixture screw and in which direction. Idle mixture screws on the Quadrajet must be adjusted equally to have a balanced air/fuel mixture. Assuming they were set properly was dumb. Yes, I should have adjusted the idle mixture screws before attempting to fine-tune the carburetor with the vacuum pressure gauge. The gauge needle, however, was somewhat erratic so I concluded that this was due to a discrepancy in the mixture screws. I adjusted the idle mixture screws and the best reading I got was about 17½-in-Hg. I used the brake booster vacuum line for the manifold vacuum source, and I adjusted the idle mixture screws with okay results since I did not have a decent baseline to work from.Īccording to my research, the ideal vacuum pressure for the Quadrajet is 18-in-Hg (inches of mercury). I didn't have one and, as you know, one cannot have too many tools. So I went ahead and purchased an inexpensive engine vacuum tester gauge online.
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