<VV> 390 Holley Carb

Rodney Sampson rsampson at swbell.net
Tue Oct 11 11:47:20 EDT 2005

  Thanks for the info, I'm looking at the Summit on-line catalog now...

Sethracer at aol.com wrote:
In a message dated 10/11/2005 8:17:31 AM Pacific Daylight Time, rsampson at swbell.net writes:

   I need to lower the vacuum at which the secondaries open .

   Anyone know how to ?   I'd like to try to increase my gas mileage.....


The secondary action is controlled by vacuum overcoming the spring in the diaphram. Holley sells kits with various strength springs to "allow" the opening of the secondary. I thinks a kit contains 5 or 6 different strengths - they are color coded, as I recall.
Acccording to Holley:
The opening rate of a vacuum secondary system is controlled by the diaphragm spring located in the vacuum secondary diaphragm housing. A “lighter” spring will allow the secondary throttle plates to open more quickly. A spring assortment kit, Holley P/N 20-13, is available to help you “tailor” the secondary opening rate to your application. A “quick change” kit, Holley P/N 20-59, is also available for fast and easy access to the spring. It consists of a two-piece secondary diaphragm housing cover which, after it’s installed, can easily cut in half the time required to change the secondary spring.
Check www.summitracing.com for easy pricing.   - Seth Emerson

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