81 stock carb
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Joined: Aug 2005
Posts: 52
Likes: 1
From: Utica New York
81 stock carb
Hello Everyone.
I have a question about the stock 4 barrel carb on my 81. Are the secondary's supposed to open up if you punch the gas when the car is in park. The engine seems to not have as much pep as it used to. I recently
replaced the ECM. It runs better now but still has no pep when i punch it.
The transmission shifts down but it feels like the secondary's are not
opening. Any suggestions?
I have a question about the stock 4 barrel carb on my 81. Are the secondary's supposed to open up if you punch the gas when the car is in park. The engine seems to not have as much pep as it used to. I recently
replaced the ECM. It runs better now but still has no pep when i punch it.
The transmission shifts down but it feels like the secondary's are not
opening. Any suggestions?
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Several issues can cause that kind of problem:
1. There is a secondary lockout lever on the lower right side of the carb. It works with the choke mechanism. If the choke is not fully open, that lockout lever will not allow the secondary throttle plates to open. That lever needs to be free to swing; if it binds up at all, it won't release to allow the secondaries to open.
2. The accelerator pedal mechanism can wear and/or bend, making it impossible to get complete cable movement to the carb linkage. To check, get engine warm then turn engine OFF and have someone sit in the driver's seat; raise hood, remove air cleaner, and hold secondary airvalve (at top of secondary openings) open so you can look down and watch the action of the secondary throttle plates. Now, have your 'helper' push the accel pedal to the floor and hold it. If the lockout lever is not preventing the plates from opening, they should be rotated 90 degrees and sitting in a vertical position. If they are not...or they don't open at all, the problem could be inadequate cable movement due to too thick of a floor mat, worn/damaged accel pedal mechanism, improper cable length adjustment, binding carb linkage, and because the carb is not mounted square on the intake and the plates are hitting the manifold gasket or manifold bores.
3. The linkage on the carb might be damaged or worn to the point that it won't work any more. Springs, levers, pivots can all wear out or become damaged.
Important: If you are going to be exercising your accel pedal to WOT position several times, it is BEST that you use a small nailset to drive the accelerator pump lever roll-pin IN (toward the carb body) so that the lever isn't functional during your testing. Otherwise, you are just squirting a bunch of raw fuel into your intake manifold. And, if the engine is fired with that much raw fuel in the manifold, LOOK OUT !!!
Don't drive the roll-pin all the way to the carb body; you will need to get a screwdriver tip in behind it to move it back into position for the lever pivot, eventually.
1. There is a secondary lockout lever on the lower right side of the carb. It works with the choke mechanism. If the choke is not fully open, that lockout lever will not allow the secondary throttle plates to open. That lever needs to be free to swing; if it binds up at all, it won't release to allow the secondaries to open.
2. The accelerator pedal mechanism can wear and/or bend, making it impossible to get complete cable movement to the carb linkage. To check, get engine warm then turn engine OFF and have someone sit in the driver's seat; raise hood, remove air cleaner, and hold secondary airvalve (at top of secondary openings) open so you can look down and watch the action of the secondary throttle plates. Now, have your 'helper' push the accel pedal to the floor and hold it. If the lockout lever is not preventing the plates from opening, they should be rotated 90 degrees and sitting in a vertical position. If they are not...or they don't open at all, the problem could be inadequate cable movement due to too thick of a floor mat, worn/damaged accel pedal mechanism, improper cable length adjustment, binding carb linkage, and because the carb is not mounted square on the intake and the plates are hitting the manifold gasket or manifold bores.
3. The linkage on the carb might be damaged or worn to the point that it won't work any more. Springs, levers, pivots can all wear out or become damaged.
Important: If you are going to be exercising your accel pedal to WOT position several times, it is BEST that you use a small nailset to drive the accelerator pump lever roll-pin IN (toward the carb body) so that the lever isn't functional during your testing. Otherwise, you are just squirting a bunch of raw fuel into your intake manifold. And, if the engine is fired with that much raw fuel in the manifold, LOOK OUT !!!
Don't drive the roll-pin all the way to the carb body; you will need to get a screwdriver tip in behind it to move it back into position for the lever pivot, eventually.
Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
The secondary air valves are demand driven. My heads + cam small block will open them up just a tad when "winged" in neutral. A stock emissions era motor likely will not. (Maybe the L-82).
Bear in mind that you do not use the secondaries at unless you're at about 65% maximum throttle angle. If you're feeling a power loss below that, your problem is not in the secondary circuit.
Bear in mind that you do not use the secondaries at unless you're at about 65% maximum throttle angle. If you're feeling a power loss below that, your problem is not in the secondary circuit.
