I've got a stock Q-Jet on a 350 1968 Skylark with 74000 original miles. The secondaries never seem to open up when I gun it except one time within the year I've owned it. What can I try to kick in some of that legendary Buick Power?
You're talking about the air valve at the top rear of the carb right? To get that to open, you'll have to look at where the rod for the air valves meets the carb body on the passangers side, and there will be a small slotted screw and near that will be alan head screw. Loosen the alan head screw, (it faces down so its hard to find) then turn the slotted screw about 1/8 of a turn counterclockwise to loosen the air valve up. Then tighten the alan screw. Make sure you keep the screw driver in the sloted screw to keep it from completely unwinding from spring tension. If that doesn't help then do the same thing loosening it up a little more every time till it starts to bog when you get into the secondaries. Then go 1/8 of a clockwise. Also check the linkage to the vacuum canister on that side and make sure it doesn't hold the valve closed when there's no vacuum ie. with the engine off.
He already said it was a Q-Jet. Therefore it has mechanical secondaries and a vacuum (velocity) air valve. 1. Plenty of Q-Jets will not open the rear throttles because the throttle shaft is stuck in the casting, or, more often, the intermediate gasket gets "squished out" and binds the throttle blades. 2. Plenty of Q-Jets will not open the air valve because the choke is not COMPLETELY opened up. There is a lockout that prevents the secondaries from flowing air when the engine is cold. The common causes are lack of a heat riser valve to direct hot exhaust to the choke coil, and a carbon-plugged manifold which will also prevent hot exhaust from heating the choke coil. Less common problems are mis-adjusted choke linkage, or defective choke mechanism. The big thing is, if the air valve is properly adjusted, you WILL NOT feel it "kick in" because the power will be smooth and seamless. Are you CERTAIN that the secondaries don't work???
Obviously I don't know that much about carbs I had an old Q-jet and broke the vacuum diaphram at the rear - effectively killing the secondaries. It was a thought.
First check that everything moves like it should. If you push down on the secondary air valve with your finger tip (engine off) it should open smoothly with slight spring pressure. (The procedure described by Steve in post #2 adjusts this tension.) The lock out mentioned hangs off the back of the primary choke tower on the passenger side. It holds the secondary air valve closed unless the choke is fully open. Personally, I would wire this thing permanently open. It is only there to keep you from going to full throttle on a cold engine, and anyone driving a classic car should know better. They have a bad habit of engaging when they are not supposed to. Next have someone push the accelerator to the floor whie you look down the carburetor to verify that the secondary throtle plates are openning (agian, engine off). Open the secondary air valve with your finger and look down into the carb. You should see the throtle plates are vertical with the accelerator to the floor. Lastly, check to be sure that as the secondary air valves open, the secondary rods are coming up. The hanger for the secondary rods runs front to back between the two secondary air valves, you should see the front of the hanger rise about 1/4"
If your choke on your primary opens fully. There is a small little hook (on my 70 carb anyway) that keeps the 2ndary valve from opening. On my car the secondarys would only open occasionally. I found that I needed to bend that small lever that touches the linkage of the primary choke valve so that it would open more consistantly. to see the mechnisim that controls the 2ndary from the choke, with the engine cold set the choke by pushing the gas to the floor. remove the air cleaner and get a good look at the carb. on the passangers side of the engine is all the choke linkage. try to push the 2ndary air valve. if it dosen't open, look for the small little hook around the edges of the valve holding it up. That little hook is on the other end of the lever that may need adjustment and from there you should be able to see what needs adjusting. the problem that I now run into is that the secondary pull off valve holds it too often for my liking. -nate
I have to pull up on the lock out mechanism for the secondaries to get the valve to open. When you say secondary air valves, I assume you mean the thing that looks like the choke but covers the intake chamber on the secondaries? There doesn't seem to be anything that could move the lock-out mechanism except my finger. No rod or spring or any other actuator is attached. I think I'll try wiring it as you said. Thanks for the info!
Guys, I speak from experience here when I suggest checking the operation of the choke. On too many occasions, I have found the choke operation erratic, causing all kinds of problems including fast idle, no secondary operation, etc. The hot air choke is typically the culprit, regardless of the type in question. Be sure of several things, including, but not limited to, choke adjustment, heat supply, the possibility of leakage of outside, cooler air, the operation of the hot air controls in the air cleaner, etc. On the hot air supply on the air cleaner, it is essential that the air be heated in the air cleaner before it is sent to the choke housing, and that the vacuum leak in the housing be open. Also, be sure that the choke plate seal on the housing is not leaking, as both of these problems are what I typically find on choke related complaints. One other thing to assure yourself of is the operation of the linkages, and the lack of ANY binding, including the choke blade itself in the housing. These linkages are approaching 40 years old, and the expertise to fix them is becoming rare. I have this expertise, and welcome any and all questions regarding their operation. Ray
