First of all a Holley with no metering block has a plate and you can't change the jets. Second of all, why Holley put PV's in the secondary metering blocks at all makes no sense at all on square bore carb. By the time your foot is in the secondaries, the vacuum is below the PV rating anyway and the secondary accelerator pump takes care of the transition. Third of all, my model # 4777 lists 71's and 76's respectively from the factory without a secondary PV. That's only a 5 size difference. Of course I'm speaking of square bore double pumper carbs only.
Care to debate? :-D Presently I'm running this carb (4777 with a Quickfuel throttle body) with 73 & 74 jets respectively on my build and all plugs look great! Every engine build will need to be jetted on an individual basis due to the myraid of configurations not only in the engine build itself but chassis weight, gearing, transmission, converter stall and altitude where the vehicle is being run. Jetting that is close to "square" is an indication of good fuel distribution and proper tuning. :)
