So...I pulled my Weird-o Holley apart, and there were all sorts of jets in there. Pulled up some numbers from Holley, and it seems that out of the box, it ran 64/90. Now, I know the rule for 1 jet size down for every 2K in altitude, so that puts me in the neighborhood of 61/87. I also know that the same carb on a 455 punched to 462, it runs great factory. Should I down my sizes even a few more considering it will be on top of a 430 with a TA212? Here's what I've got. 67 430. TA212 cam. top half rebuild. all stock besides cam. 4011 Holley dual feed, single pump, vacuum secondaries. I know that without testing, nobody can just magically give me the right numbers. A ball park idea would be nice though. Thinking maybe 60/84? Thanks guys!
I would start with the Holley jetting, with your altitude correction factored in, as long as you took care to maintain a power valve, if it came that way from the factory. If you have deleted the power valves, then jet up 8-10 sizes. The carb is jetted from the factory to provide the correct air fuel mixture, at a given altitude and temp, on a "standard" engine.. meaning it has a "normal" ability to produce vacuum. The size of the engine (hence an increase in airflow) is not a relevant factor for changing jets. The carb is jetted to be a metering device, that is correct unto itself, considering the venturi sizes and configurations, as well as the air bleeds, of that particular unit. It should work on virtually any engine, of any airflow, as long as it can provide that airflow. Example.. Ron at the dyno shop has a 1000 cfm Holley.. he has never changed a jet in it, as his dyno cell is a "standard" set of atmospheric conditions, varying only slightly on the barometer, due to weather changes. That carb has run on 500 HP small blocks, and 800 HP big blocks, and metered fuel with an acceptable parameter on each engine. Jet changing is more for fine tuning, to account for varying weather conditions, and to be honest about it, a carb will run pretty much the same over a fairly wide range in tuning. The only time this will change is when you get into an engine with radical camshaft timing, which creates a low vacuum signal to the carburetor, and then you may have to work with the idle and transition circuits, in a Holley to a point, that is as easy as adjusting the idle mixtures screws. JW
