I have an original Stage 1 rochester carb. and i doesnt seem to be running quite right. Normal slow accelleration is fine but when i jump on it off the line it boggs down like the distributer cant keep up with the acceleration or it might be the fule accelerator pump, either giving to little fule for the air flow or too much im not really sure. ANY SUGESTIONS!!
Yes, check the air valves at the top of the carb, above the secondary throttle plates. Their job is to size the carburetor air flow to engine demand. If they flop in too quickly, it feeds more air to the engine then it can handle at low RPM. They are supposed to tip in gradually. There are 2 things that control the air valve action. One is the spring windup on the air valve shaft. With the engine off push the air valves open, and remove your finger. They should snap back without sticking. The second thing is the primary vacuum break on the passenger side front of the carb. There is a metal rod linking the vacuum break to the air valves. When you floor the car from low speed, the vacuum goes to 0, the vacuum break releases it hold on the air valves and allows them to slowly tip in. With the engine running, try to push the air valves in. You should not be able to, if the vacuum break is working. If you can, it is defective, replace it.
Just got through solving the same problem on my Q-jet. It's most likely the secondaries opening too soon, see the above post. The best way to track down the problem is to block off the secondaries so they won't open, then go for a drive. On the passenger side, there should be a little 'foot' shaped link that the choke linkage lifts up to hook a pin in the end of the secondary throttle. Take a bread twist-tie or something, and tie the link up so that the secondaries won't open. (Mine has the link removed, so I had to remove the actuating link on the throttle side.) If it still bogs, look to the primary side, you're best off getting a carb kit and making sure everything inside is CLEAN. (most likely the accelerator pump/passages/checkballs/nozzles.) If it's the secondary side, first look at the vacuum dashpot as in above post, if it's ok, then check the air valve windup spring. It's on the passenger side of the air valve ("choke" looking plate on secondary side). Right behind the end of the air valve shaft, there is a small flathead screw, it winds up the return spring, which you can feel under the top carb casting (air horn). There is a SMALL hex-head locking screw that comes up from under the screw. Loosed the locking screw, and adjust the windup spring 1/2 turn past the point where it just contacts the pin on the air valve shaft (1/2 turn of pressure on air valve shaft.) Lots of "performance tuners" will loosen the windup spring, thinking that they are opening up the secondaries sooner for more power. All they cause is an excessively lean condition when they start to open, hence the "Infamous Q-jet Bog". In my not-even humble opinion, Q-jets are the best carbs ever made! Their only problem is that most folks would rather spend $$$ for a Holley (inferior design, fuel leaks, blown valves, JUNK) than learn how to work on the Q-jet they already have. James
