Car not making power 2700 rpm and up in first...
07-08-2002, 12:21 AM
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Car: 84 Z28
Car not making power 2700 rpm and up in first...
When I floor it, it seems like the car stops making power once it hits 2700 rpm. I checked the timing and it is dead on. It seems to only be in first gear. The only other problem I can really think of with the car is bad valve seals and sometimes it seems to misfire at lower RPM's when I start driving it and it hasn't been on long. It is an L69 engine, no codes are being thrown.
07-09-2002, 02:30 PM
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Car: 4
Engine: 6
Transmission: 5
The air valve itself should be closed when the car is jsut sitting there; you can push on it and open it, there should be a noticeable amount of tension. The adjustment itself is a little screw that looks like it would be in line with its shaft, on the pass side of the carb; there is a lock screw for the adjustment, which is underneath the air horn, it's a 5/64" Allen IIRC.
To adjust the tension, loosen the set screw; the tension will all go away, and the air valve will become floppy. Put your little (1/8" IIRC) screwdriver in the adjuster screw, and turn it clockwise until it just barely starts exerting tension on the air valve; then continue to turn it clockwise to apply the desired tension. Then while holding the tension where you want it, tighten the set screw.
Optimum tension for a 305 is usually between 5/8 and 7/8 turn. It's a tunung adjustment, so feel free to experiment until you get the effect you want.
The "bog" is usually caused by not enough tension; the air valve will flop open, the velocity through the venturi will be very low, the carb will meter no fuel, and the engine goes waaayyyy lean. Too tight, and the secondaries will be too rich. People seem to think that they can get rid of the bog by loosening the valve; this is backwards.
There are some other things that control air valve opening rate, and then other things that control the fuel mixture at various points as it opens. The choke pulloff diaphragm in particular retards the AV opening so that it doesn't flood the engine with air by opening too quickly. If you still have the original L69 carb, you already have a good set of metering parts.
To adjust the tension, loosen the set screw; the tension will all go away, and the air valve will become floppy. Put your little (1/8" IIRC) screwdriver in the adjuster screw, and turn it clockwise until it just barely starts exerting tension on the air valve; then continue to turn it clockwise to apply the desired tension. Then while holding the tension where you want it, tighten the set screw.
Optimum tension for a 305 is usually between 5/8 and 7/8 turn. It's a tunung adjustment, so feel free to experiment until you get the effect you want.
The "bog" is usually caused by not enough tension; the air valve will flop open, the velocity through the venturi will be very low, the carb will meter no fuel, and the engine goes waaayyyy lean. Too tight, and the secondaries will be too rich. People seem to think that they can get rid of the bog by loosening the valve; this is backwards.
There are some other things that control air valve opening rate, and then other things that control the fuel mixture at various points as it opens. The choke pulloff diaphragm in particular retards the AV opening so that it doesn't flood the engine with air by opening too quickly. If you still have the original L69 carb, you already have a good set of metering parts.
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