Quote:
Originally Posted by 94cobra69ss396
I found this on FordMuscle.com after I found out what I thought was wrong.
"When it comes to Holleys, 4150 and 4160 refer to the two most popular models of Holley carbs. A 4150 has both primary and secondary metering blocks, allowing you to change jetting for both the primary and secondary circuits. The 4160 models utilize a metering plate in the secondary , which has fixed, non-adjustable, metering orifices. All 4160 models have vacuum actuated secondary throttle plates. The 4150 models come in either dual mechanical throttle plates or with vacuum secondaries. All 4150's have dual accelerator pumps, and dual fuel inlets hence the term "double pumper." The difference between vacuum and mechanical secondaries is simply in how the carb actuates the secondary metering system. In vacuum actuated carbs, the secondaries open up only when the vacuum across the primary venturis reaches a certain level. A diaphragm housing on the side of the carb contains a changeable spring which controls precisely when the secondaries open. On a mechanical secondary carb the secondaries open when the throttle lever reaches a certain position. The simplest way to tell which type you have is to look down the throat of the carb, with the engine off, and pull back on the throttle lever. If the secondaries open, its a mechanical secondary."
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Now I see what you mean. Yea, if you look at it that way 4160 would all be Vac Secondaries. But, 4150 and 4160 is determined by metering blocks--the Vac Secondary thing is just a by line. But, could be true if you want to look at it as a Vac Secondary only.
