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