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Re: [GMCnet] Injection versus Carbs [message #74259 is a reply to message #73254] |
Thu, 18 February 2010 15:08 |
Larry
Messages: 2875 Registered: January 2004 Location: Menomonie, WI
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The Altitude Compensating carbs work great...UNLESS...you have a Wide band O2 and a FA meter. Now that sounds strange, but the FA tells you what the carb is *really* doing in terms of FA at all speeds,throttle positions and loads. If yo hav ethe O2 meter, I can guarentee, you'r gonna want to change something. In the Q-jet, each curcuit (idle, part throttle, primary circuit, power inrichment, WOT primary, part throttle secondary, all in between throttle positions in the secondary, and WOT secondary) all have an effect on the others. Change the idle screws by opening them up a bit for a richer mixture at idle and it richens up all of the other throttle positions...though to a more minor degree, the wider open the throttle gets. A change in jets or rods directly effects not only the primary, but the secondary circuit. Change the power piston spring, it changes the entire primary circuit enrichment cycle relative to throttle position. In the secondary, while the jet is fixed, there is a nearly infinate (exaggerating)number of secondary rods...each of which has it's own enrichment curve depending on vacuum, and throttle position.
So, now with the Altitude Compensating carb, add in one more power valve with yet another rod to the primary circuit, and an aneroid that is hooked to a rod and is adjustable like the APT, and suddenly you have more variables than you can imagine. After playing with it for several months, I finally gave up trying to tune it for the FA's that I wanted at the different throttle positions and loads, and got a Q-jet with a Adjustable Part Throttle (APT) off of a, IIRC...81'chevy 454 PU. I'm finally getting close to what I want and i'm changing to a MPI. Why???...because it's there....and I can make changes with a laptop instead of having to take the Carb apart.
IMO, unless you know what you are doing and have a FA meter to compliment your tuning procedure, you have no business changing rods, jets, or making ATP, or any other adjustments to a q-jet. To lean, and you could burn up a motor...to rich and you contaminate the oil with washed down fuel doing over the long term, damage to your motor. If you are not sure of what you are doing, get a Patterson Carb, and be happy with it. JMHO
Larry
78 Royale w/500 Caddy
Menomonie, WI.
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[GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: Ron on Mon, 08 February 2010 11:08
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: k2gkk on Mon, 08 February 2010 12:35
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: Larry on Mon, 08 February 2010 22:00
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: Ron on Mon, 08 February 2010 14:31
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: tgeiger on Tue, 09 February 2010 09:51
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: USAussie on Mon, 08 February 2010 16:23
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Re: [GMCnet] Injection versus Carbs
By: Larry C on Thu, 18 February 2010 09:06
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: Chr$ on Mon, 08 February 2010 16:48
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Re: [GMCnet] Injection versus Carbs
By: Chr$ on Mon, 08 February 2010 16:49
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Re: [GMCnet] Injection versus Carbs
By: k2gkk on Mon, 08 February 2010 18:12
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: tgeiger on Wed, 10 February 2010 14:37
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Re: [GMCnet] Injection versus Carbs
By: ljdavick on Wed, 10 February 2010 14:45
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: Ron on Sat, 13 February 2010 16:14
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Re: [GMCnet] Injection versus Carbs
By: Surbo on Sat, 13 February 2010 17:45
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Re: [GMCnet] Injection versus Carbs
By: Ron on Sat, 13 February 2010 17:57
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: Larry on Mon, 15 February 2010 14:40
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Re: [GMCnet] Injection versus Carbs
By: mlincoln on Mon, 15 February 2010 15:31
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: mlincoln on Wed, 17 February 2010 19:31
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: Kosier on Wed, 17 February 2010 21:46
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Re: [GMCnet] Injection versus Carbs
By: mlincoln on Wed, 17 February 2010 22:01
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Re: [GMCnet] Injection versus Carbs
By: Kosier on Wed, 17 February 2010 22:34
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: mlincoln on Thu, 18 February 2010 08:38
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Re: [GMCnet] Injection versus Carbs
By: Kosier on Wed, 17 February 2010 20:57
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Re: [GMCnet] Injection versus Carbs
By: Surbo on Mon, 15 February 2010 14:09
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: jimk on Wed, 10 February 2010 22:18
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: psakw on Sat, 13 February 2010 21:58
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: g.winger on Thu, 18 February 2010 14:11
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Re: [GMCnet] Injection versus Carbs
By: Larry on Thu, 18 February 2010 15:08
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Re: [GMCnet] Injection versus Carbs
By: wally on Thu, 18 February 2010 15:33
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Re: [GMCnet] Injection versus Carbs
By: Larry on Fri, 19 February 2010 13:44
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Re: [GMCnet] Injection versus Carbs
By: wally on Fri, 19 February 2010 14:44
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Re: [GMCnet] Injection versus Carbs
By: Larry on Fri, 19 February 2010 19:05
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: Keith V on Sat, 20 February 2010 10:12
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Re: [GMCnet] Injection versus Carbs
By: GMC_LES on Sat, 20 February 2010 16:45
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Re: [GMCnet] Injection versus Carbs
By: WD0AFQ on Sat, 20 February 2010 17:35
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