vaccuum gauge readings - Team Camaro Tech
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post #1 of 7 (permalink) Old Feb 9th, 11, 07:18 PM Thread Starter
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Shane
 
Join Date: Apr 2007
Location: Alabama
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vaccuum gauge readings

Been trying to tune my holley carb and finally decided to get a vaccum gauge to help. I have a big block with a mild cam nothing real radical( I can provide info on cam if anyone interested 770 street avenger carb) and I am running around 15 inches vaccuum after tuning this seems to be about the best I can get at idle. I have the gauge hooked up to a port on the carb itslef. From what I understand this is not bad for a motor with a mild cam like I have.

My question is should this reading stay steady at all times or is it normal for it to fluctuate when I rev the engine?

Thanks in advance,
Shane
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post #2 of 7 (permalink) Old Feb 9th, 11, 07:22 PM
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Steiner
 
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Re: vaccuum gauge readings

If you rev it out of gear there is no load so you'll see it initially dip and then shoot up. If you hold the pedal down a bit it'll rise. Once you put a load on it it'll drop.

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post #3 of 7 (permalink) Old Feb 9th, 11, 07:36 PM Thread Starter
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Shane
 
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Re: vaccuum gauge readings

Quote:
Originally Posted by Steiner View Post
If you rev it out of gear there is no load so you'll see it initially dip and then shoot up. If you hold the pedal down a bit it'll rise. Once you put a load on it it'll drop.
Thanks for the quick reply. The book I have does say reading should stay constant so I guess that means at idle it just was not that clear so again thanks for the response.

Shane
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post #4 of 7 (permalink) Old Feb 9th, 11, 07:40 PM
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Steve
 
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Re: vaccuum gauge readings

Check this out.. http://www.secondchancegarage.com/public/186.cfm

69 SS, 350/300 h.p., M-20, 12 bolt, matching numbers.


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post #5 of 7 (permalink) Old Feb 9th, 11, 09:08 PM
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Steps
 
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Re: vaccuum gauge readings

Mild cam = inefficent at low rpms = low vac at idle, unless the the idle timing is increased.
Do this by adding more VA..increasing Cent intial too far loads the strter up, causing armiture issues
Regardless.. just tune the carb at a give advance to the highest vaccuum, then turn the mixturev screws in (lean) 1/4 turn

DO NOT 'tune' the timing with a vaccuum gauge OR by ear..unless u want to increasae NOx to high levels and start burning valves, melting holes inj pistons and eventually throwing bearings
Covered in many old threads in detail and how toos

Every car should have an in
car vac gauge

My Spelling is not incorrect...it is creative

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post #6 of 7 (permalink) Old Feb 10th, 11, 06:05 AM Thread Starter
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Shane
 
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Re: vaccuum gauge readings

Quote:
Originally Posted by reelknots View Post
Great info thanks a lot. Shane
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post #7 of 7 (permalink) Old Feb 12th, 11, 03:22 PM
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Mike
 
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Re: vaccuum gauge readings

Quote:
Originally Posted by reelknots View Post
Good stuff thx for the info


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