Holley NH idle circuit

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mike zahorik
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Holley NH idle circuit

Post by mike zahorik » Thu Oct 01, 2020 3:37 pm

On the Holley NH carburetor, why are there two idle circuit holes near the throttle plate? Seems that when the throttle is closed, the back, larger hole is on the non vacuum side side of the throttle plate and the smaller hole is on the vacuum side. Does the larger hole act an air bleed until the throttle is opened to the point where the larger hole is more influenced by the engine vacuum? Then the larger hole also provides more idle gasoline until the throttle is opened where the venturi starts to function? Thanks Mike.

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DanTreace
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Re: Holley NH idle circuit

Post by DanTreace » Thu Oct 01, 2020 4:38 pm

The Service Bulletin explains these two holes, Extreme Idle D and Low Speed E.


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Steve Jelf
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Re: Holley NH idle circuit

Post by Steve Jelf » Thu Oct 01, 2020 11:48 pm

Here's a little bit better copy. Volume 5, #2 — February 1924.

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Topic author
mike zahorik
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Re: Holley NH idle circuit

Post by mike zahorik » Fri Oct 02, 2020 7:00 pm

Thanks, Mike

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