TaMpAToNy69: You have never stated what is in it now and if you have a PV? If you have the power valve I would run aproximately what Levi is saying, but if you plug the PV you need to go about 8 sizes bigger. Every day that goes by I learn more about what the Holley gives and what the rotary wants! Something I am in the process of learning is, the leaner you run seems to have a better top end and the richer seems to have a better low end. So Iam thinking now, is to get the 50cc accelerator pump with bigger cam and lean out jets a little, so my low end lean stumble I have created with leaning of the jets (65prim - 59secs) should disappear with the bigger squirt of gas down in the low rpm's. My theory being to richen my low end and lean my top end, since the Holley is infomous for their rich top end, because of the small air bleeds. Hopefully I can get it right with out having to fuck with the air bleeds, because the air bleed are not adjustable in the 4160/4150. And can easily screw up a perfectly good carb if you start drilling holes ! ! !