Missing idle adjusting needles?

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Jul 31, 2005 | 05:52 PM

yellow71

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Instructor

Joined: Oct 2004

Posts: 124

Likes: 1

Missing idle adjusting needles?

Just discovered something possibly significant with my stock Holley model 4150 on 71 LT1. My forward metering plate has an idle mixture screw in both sides of the plate (2) and my secondary plate (rear) does not have any (holes empty on both sides).
My Haynes Holley manual shows adjusting screws in all four holes. Is this correct? I know mine has never had more than 2.

What is the correct setup? If only 2, which holes do they go in?

Maybe this is why I can't get the idle right.

Thanks
Neil

Jul 31, 2005 | 07:50 PM

Vetterodder

Safety Car

Joined: Feb 1999

Posts: 3,631

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From: Fountain Hills AZ

Some 4150's do have 4 corner idle adjustment but not all. It sounds like your manual is talking about an after market DP, not the stock type vacuum secondary 4150.

Jul 31, 2005 | 10:01 PM

yellow71

Thread Starter

Instructor

Joined: Oct 2004

Posts: 124

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So if you do have 4 idle screws how do you adjust idle? Go for a drop/rise on each one? My manual clearly shows 4 idle screws one on each corner and my carb has the openings for them.

Can anyone with a stock 71 LT1 look at the and tell me how many idle screws you have.

Thanks again
Neil

Jul 31, 2005 | 11:48 PM

b71vette

Burning Brakes

Joined: Jan 2004

Posts: 1,043

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From: Va

Yep only 2 were on my 71 LT1 orig Holley

Best way is to use a vacuum gauge when setting idle mixture.

Aug 1, 2005 | 12:57 AM

Solid LT1

Le Mans Master

Joined: Dec 2003

Posts: 5,727

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From: Fremont CA

You will only have adjusting screws on the primary metering block on any factory Holley.

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