Saw someone ask about the different throttle plates on a forum the other day. So here: Why are some throttle plates thicker than others? In the case of 172 and 173 as shown, the thinner plates almost never seal as well. With closed throttle airflow moving in the primaries more and the secondaries closed, the pull seen at the fuel bleeds is vastly different. Primary plates don’t need to seal as well as they are going to be held open to attain no load idle speed. Some carbs like Cobrajets are...

So to explain what these are as invariably a bunch of people will decide to throw their opinions around without much back info. Before someone says “oh those are 660s!” They are not. These are from 67-68. Center squirters were not available until later 69 (I believe). These are the second evolution of the center squirter. The first hand made ones I have seen are from 1965. In the 1960s (and before) Ford and Holley were very intertwined. Just about any performance Ford came with a highly...

How to read the “Holley Black book.” Part #36-51 1. Find the part in question (I normally double check jet and pv) 2. Find part on the chart 3. Look up and cross reference it with your list number. In this case, List 4511 jet size is 68 and 82. Throttle plates 224/172 Pump nozzle .026 Metering blocks 6211/6213 Power valve 6.5 Etc