quadrajet 455ho

[ss3011]

Originally Posted by gearhead63

the car is a 1972 lemans no ramair hood no aircleaner no primary rods just jets secondary metering rod holes are sealed float level 1/2 in fuelpressure 6psi accelerating well tubes are blockt afr 12.5-13.5 in second and third gear. regards magnus

Was the float level and the accelerator well tubes modified that way to try and fix this rich problem ? Not sure what you are talking about when referring to accelerating well tubes . Are these the tubes that are supposed to feed fuel into the secondaries as the flaps start to open ? Also when you are on the 2 step , are you flooring the accelerator pedal ?

[gearhead63]

float level 1/2in accelerating tubes are the tubes that feed fuel into the secondaries when the flaps opens they were seald to try to fix the problem. yes the pedal is floored on the 2 step.

[ss3011]

Originally Posted by gearhead63

float level 1/2in accelerating tubes are the tubes that feed fuel into the secondaries when the flaps opens they were seald to try to fix the problem. yes the pedal is floored on the 2 step.

Apparently you have some sort of data acquisition system , assuming you are measuring A/F ratio with a wide band O2 sensor . When on the 2 step , what is the A/F ratio ? Once you release the 2 step , what is the A/F ratio ? Is the A/F ratio consistent at 11.5 through out 1st gear , then goes to 12.5-13.0 after the shift to second ?

[gearhead63]

yes we have a racepack. after releasing the 2stepp the afr goes from 10.5 to 12 att the first to second shift after that it varies between 12.5 to 13.5.

[ss3011]

Originally Posted by gearhead63

yes we have a racepack. after releasing the 2stepp the afr goes from 10.5 to 12 att the first to second shift after that it varies between 12.5 to 13.5.

What is hard to understand , is usually when your on the two step the O2 sensor is faked out , and will read very lean . This is because the two step interrupts the ignition which means some cylinders don't fire and the air passes right through the engine , and the O2 sensor reads that as excess O2 and therefore lean . Yours is reading rich , which is opposite from what I would expect . You may want to make a run without running the two step and compare the results .

[Hacksaw]

I firmly agree you have too much main jet. I think you should change the primary jets to # 68, then evaluate.

[Jeff Stout]

Originally Posted by ss3011

What is hard to understand , is usually when your on the two step the O2 sensor is faked out , and will read very lean . This is because the two step interrupts the ignition which means some cylinders don't fire and the air passes right through the engine , and the O2 sensor reads that as excess O2 and therefore lean . Yours is reading rich , which is opposite from what I would expect . You may want to make a run without running the two step and compare the results .

I always thought the opposite. Unburned fuel from 2 step going out exhaust and making a rich condition. My bracket car has a O2 reader and on 2 step it is rich and gets right by second gear shift. Yes on to big primary with no rods.

[ss3011]

Originally Posted by Jeff Stout

I always thought the opposite. Unburned fuel from 2 step going out exhaust and making a rich condition. My bracket car has a O2 reader and on 2 step it is rich and gets right by second gear shift. Yes on to big primary with no rods.

In a production car , when the engine misfires the O2 sensor reads lean , and then starts to add more fuel to correct . Most production calibrations will only allow so much correction , and once it reaches that limit , it sets a code . A misfire is similar to what a two step does only more controlled . I am surprised your engine reads rich when on the two step . Hopefully a few more folks will chime in with their experiences .

As far as running as big a jet with no rods , I agree , too big , but remember that this particular carb has the POE system , which adds even more fuel into the primaries at WOT . He might have to put a very small primary jet , or reinstall the power piston and primary rods .