| Quadrajet Idle Circuit [message #80873] |
Sat, 17 April 2010 20:12  |
Frank Condos
Messages: 90
Registered: March 2004
Karma: 0
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While I hunt for my Doug Roe Rochester book, does anyone know if I should see the fuel flow from above the throttle plate during idle? Both barrels uniform spray, 800 RPM 15" vac, a slight idle miss. Performs great while driving.
From memory I thought the idle cirduit fed below the throttle plates. Any help?
Frank Condos
Ahwahnee. CA
Come to Auburn next month
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| Re: Quadrajet Idle Circuit [message #80893 is a reply to message #80873] |
Sun, 18 April 2010 07:20  |
g.winger
Messages: 792
Registered: February 2008
Location: Warrenton,Missouri
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You might go see and post on Cliff Ruggles forum. He,s a great help and his book is excellent. Read it 3 times.
www.cliffshighperformance.com,,,,,he,s stated many times that ignition problems will mask carb problems. GL,,,PL
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| Re: [GMCnet] Quadrajet Idle Circuit [message #80943 is a reply to message #80893] |
Sun, 18 April 2010 18:06 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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The main difference between a car carb. and a truck/motor home is the
power valve.
Power valve on a car opens as low as 14" wg, while the GMC will not
open until 11"wg.
We supply both Springfield units from D Patterson and also our local carb shop.
I make sure the local carb guy knows the difference between the two
every time we send couple units for rebuilding.
On Sun, Apr 18, 2010 at 5:20 AM, Paul Leavitt <leavittpaul@yahoo.com> wrote:
>
>
> You might go see and post on Cliff Ruggles forum. He,s a great help and his book is excellent. Read it 3 times.
> www.cliffshighperformance.com,,,,,he,s stated many times that ignition problems will mask carb problems. GL,,,PL
> _______________________________________________
> GMCnet mailing list
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--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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Jim Kanomata
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jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: Quadrajet Idle Circuit [message #80981 is a reply to message #80873] |
Sun, 18 April 2010 21:21 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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From what I know the answer is no. You should not see fuel coming from the primary booster venturis at idle. 800 is a touch fast, but I would think not. Try it at like 650 and see what happens. If you still see fuel the first think I would check is float level.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Quadrajet Idle Circuit [message #80987 is a reply to message #80873] |
Sun, 18 April 2010 21:38 |
Larry
Messages: 2875
Registered: January 2004
Location: Menomonie, WI
Karma: 10
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Frank,
Possibly...Just above the idle circuit orifice is a vertical slot. When the throttle is closed, the bottom half of the slot is below the throttle plate, and top half is above. it's purpose is to feed fuel to act as a transition from idle to intermediate circuit. Depending on how high the float is and amount of vacuum, it may or may not have fuel visable above the throttle plate. If there is a lot of fuel, your float may be set to high or if it is a composite float, the outer coating may have partly disolved from these new fuel blends and may be sinking. In either case, I'd check the float for proper level and weigh it. Can't remember what the weight is suppose to be, but Roe's should have it. 15" of vacuum seems low for idle. IMO should be around 18" or higher. Could be excessively rich mixture because of float. Might be worth checking.
Say Hi to Freddy for us...miss seeing you two...
Larry 
78 Royale w/500 Caddy
Menomonie, WI.
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