quadrajet 455ho

[gearhead63]

the primary jet is 74 leaving off the two step att 2600 converter locksupp att 5100 condition gets better between 5900-6300 and in second and third gear

[FSA1673]

Your primary jet is too large based on my experience for not using primary rods. I run a 65 jet and have gone to 63s on the primary side with a very similar combo. The pump shot puts a fair amount of fuel when you mat it on the two step and it could cause it to run rich at the start. Are the secondary vent tubs plugged when you remove the air horn? I do not run a two step but someone with experience may be able to help. Have you tried foot braking to see if the AFR is where it should be. The other thing to check is the air door spring tension. If the air door does not open fast enough it will run rich, if it opens too quick it will create a lean bog.

[gsa612]

Originally Posted by gearhead63

the primary jet is 74 leaving off the two step att 2600 converter locksupp att 5100 condition gets better between 5900-6300 and in second and third gear

That's way too rich if your running a fixed jet (no rods).The general rule is to be 5 steps leaner than with a rod.You should be around 67 possibly leaner.Your float level at 1/2" is too low,it should be around 1/4 ".I would think at that level it would lean out due to lack of fuel in the bowl. It's hard to keep the needle on the seat when the fuel level is that low.A q-jet has a small fuel bowl to start with.When you build your fuel system you should have a pump with good volume and 1/2" lines to keep the bowl full.And keep your pressure low (6-6 1/2 lbs) for a clean leave. gsa612

[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.