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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

Karma:

Senior Member

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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[Message index]

		[GMCnet] Injection versus Carbs By: Richard Lister on Mon, 08 February 2010 10:01
		Re: [GMCnet] Injection versus Carbs By: Mr ERFisher on Mon, 08 February 2010 10:10
		Re: [GMCnet] Injection versus Carbs By: GeorgeRud on Mon, 08 February 2010 10:17
		Re: [GMCnet] Injection versus Carbs By: Ron on Mon, 08 February 2010 11:08
		Re: [GMCnet] Injection versus Carbs By: Matt Colie on Mon, 08 February 2010 11:14
		Re: [GMCnet] Injection versus Carbs By: Steven Ferguson on Mon, 08 February 2010 12:25
		Re: [GMCnet] Injection versus Carbs By: k2gkk on Mon, 08 February 2010 12:35
		Re: [GMCnet] Injection versus Carbs By: Mr ERFisher on Mon, 08 February 2010 12:46
		Re: [GMCnet] Injection versus Carbs By: Steven Ferguson on Mon, 08 February 2010 18:31
		Re: [GMCnet] Injection versus Carbs By: Larry on Mon, 08 February 2010 22:00
		Re: [GMCnet] Injection versus Carbs By: Steven Ferguson on Tue, 09 February 2010 07:19
		Re: [GMCnet] Injection versus Carbs By: bill schurman on Mon, 08 February 2010 13:11
		Re: [GMCnet] Injection versus Carbs By: Ron on Mon, 08 February 2010 14:31
		Re: [GMCnet] Injection versus Carbs By: Ken Burton on Tue, 09 February 2010 02:11
		Re: [GMCnet] Injection versus Carbs By: Jim Bounds on Tue, 09 February 2010 06:40
		Re: [GMCnet] Injection versus Carbs By: tgeiger on Tue, 09 February 2010 09:51
		Re: [GMCnet] Injection versus Carbs By: Jim Bounds on Wed, 10 February 2010 07:57
		Re: [GMCnet] Injection versus Carbs By: Jim Galbavy on Mon, 08 February 2010 15:30
		Re: [GMCnet] Injection versus Carbs By: USAussie on Mon, 08 February 2010 16:23
		Re: [GMCnet] Injection versus Carbs By: Larry C on Thu, 18 February 2010 09:06
		Re: [GMCnet] Injection versus Carbs By: Jim Bounds on Thu, 18 February 2010 11:17
		Re: [GMCnet] Injection versus Carbs By: Gary Worobec on Thu, 18 February 2010 11:33
		Re: [GMCnet] Injection versus Carbs By: Chr$ on Mon, 08 February 2010 16:48
		Re: [GMCnet] Injection versus Carbs By: Chr$ on Mon, 08 February 2010 16:49
		Re: [GMCnet] Injection versus Carbs By: k2gkk on Mon, 08 February 2010 18:12
		Re: [GMCnet] Injection versus Carbs By: Rick Williams on Mon, 08 February 2010 18:45
		Re: [GMCnet] Injection versus Carbs By: David L Greenberg on Mon, 08 February 2010 19:55
		Re: [GMCnet] Injection versus Carbs By: George Beckman on Mon, 08 February 2010 20:14
		Re: [GMCnet] Injection versus Carbs By: Matt Colie on Tue, 09 February 2010 13:25
		Re: [GMCnet] Injection versus Carbs By: Richard Lister on Tue, 09 February 2010 14:36
		Re: [GMCnet] Injection versus Carbs By: George Beckman on Tue, 09 February 2010 20:50
		Re: [GMCnet] Injection versus Carbs By: GeorgeRud on Tue, 09 February 2010 15:04
		Re: [GMCnet] Injection versus Carbs By: Jim Galbavy on Tue, 09 February 2010 15:54
		Re: [GMCnet] Injection versus Carbs By: Jim Galbavy on Tue, 09 February 2010 17:03
		Re: [GMCnet] Injection versus Carbs By: Jim Bounds on Wed, 10 February 2010 05:41
		Re: [GMCnet] Injection versus Carbs By: klassic kampers on Tue, 09 February 2010 17:34
		Re: [GMCnet] Injection versus Carbs By: Bob de Kruyff on Tue, 09 February 2010 18:35
		Re: [GMCnet] Injection versus Carbs By: Sandra Price on Wed, 10 February 2010 11:18
		Re: [GMCnet] Injection versus Carbs By: tgeiger on Wed, 10 February 2010 14:37
		Re: [GMCnet] Injection versus Carbs By: ljdavick on Wed, 10 February 2010 14:45
		Re: [GMCnet] Injection versus Carbs By: Jim Bounds on Sat, 13 February 2010 08:20
		Re: [GMCnet] Injection versus Carbs By: Bill Freeman on Sat, 13 February 2010 09:01
		Re: [GMCnet] Injection versus Carbs By: emerystora on Sat, 13 February 2010 09:47
		Re: [GMCnet] Injection versus Carbs By: Bill Freeman on Sat, 13 February 2010 15:47
		Re: [GMCnet] Injection versus Carbs By: Ron on Sat, 13 February 2010 16:14
		Re: [GMCnet] Injection versus Carbs By: Surbo on Sat, 13 February 2010 17:45
		Re: [GMCnet] Injection versus Carbs By: Ron on Sat, 13 February 2010 17:57
		Re: [GMCnet] Injection versus Carbs By: Bill Freeman on Mon, 15 February 2010 13:33
		Re: [GMCnet] Injection versus Carbs By: emerystora on Mon, 15 February 2010 13:42
		Re: [GMCnet] Injection versus Carbs By: Larry on Mon, 15 February 2010 14:40
		Re: [GMCnet] Injection versus Carbs By: mlincoln on Mon, 15 February 2010 15:31
		Re: [GMCnet] Injection versus Carbs By: Bill Freeman on Tue, 16 February 2010 07:49
		Re: [GMCnet] Injection versus Carbs By: Matt Colie on Wed, 17 February 2010 17:34
		Re: [GMCnet] Injection versus Carbs By: GMCWiperMan on Wed, 17 February 2010 17:57
		Re: [GMCnet] Injection versus Carbs By: mlincoln on Wed, 17 February 2010 19:31
		Re: [GMCnet] Injection versus Carbs By: Ken Burton on Wed, 17 February 2010 20:23
		Re: [GMCnet] Injection versus Carbs By: Kosier on Wed, 17 February 2010 21:46
		Re: [GMCnet] Injection versus Carbs By: mlincoln on Wed, 17 February 2010 22:01
		Re: [GMCnet] Injection versus Carbs By: Kosier on Wed, 17 February 2010 22:34
		Re: [GMCnet] Injection versus Carbs By: klassic kampers on Thu, 18 February 2010 14:22
		Re: [GMCnet] Injection versus Carbs By: Jim Bounds on Thu, 18 February 2010 09:09
		Re: [GMCnet] Injection versus Carbs By: Matt Colie on Thu, 18 February 2010 07:49
		Re: [GMCnet] Injection versus Carbs By: mlincoln on Thu, 18 February 2010 08:38
		Re: [GMCnet] Injection versus Carbs By: Kosier on Wed, 17 February 2010 20:57
		Re: [GMCnet] Injection versus Carbs By: Surbo on Mon, 15 February 2010 14:09
		Re: [GMCnet] Injection versus Carbs By: Jim Galbavy on Mon, 15 February 2010 14:38
		Re: [GMCnet] Injection versus Carbs By: Bill Freeman on Tue, 16 February 2010 07:38
		Re: [GMCnet] Injection versus Carbs By: Carleton Douglas[1] on Wed, 10 February 2010 14:53
		Re: [GMCnet] Injection versus Carbs By: jimk on Wed, 10 February 2010 22:18
		Re: [GMCnet] Injection versus Carbs By: Richard Lister on Tue, 16 February 2010 10:55
		Re: [GMCnet] Injection versus Carbs By: bryant374 on Tue, 16 February 2010 12:21
		Re: [GMCnet] Injection versus Carbs By: Bill Massey on Tue, 16 February 2010 13:24
		Re: [GMCnet] Injection versus Carbs By: psakw on Sat, 13 February 2010 21:58
		Re: [GMCnet] Injection versus Carbs By: emerystora on Sat, 13 February 2010 22:07
		Re: [GMCnet] Injection versus Carbs By: rallymaster on Thu, 18 February 2010 11:45
		Re: [GMCnet] Injection versus Carbs By: g.winger on Thu, 18 February 2010 14:11
		Re: [GMCnet] Injection versus Carbs By: Larry on Thu, 18 February 2010 15:08
		Re: [GMCnet] Injection versus Carbs By: wally on Thu, 18 February 2010 15:33
		Re: [GMCnet] Injection versus Carbs By: Larry on Fri, 19 February 2010 13:44
		Re: [GMCnet] Injection versus Carbs By: wally on Fri, 19 February 2010 14:44
		Re: [GMCnet] Injection versus Carbs By: Larry on Fri, 19 February 2010 19:05
		Re: [GMCnet] Injection versus Carbs By: GMCWiperMan on Fri, 19 February 2010 19:23
		Re: [GMCnet] Injection versus Carbs By: Keith V on Sat, 20 February 2010 10:12
		Re: [GMCnet] Injection versus Carbs By: GMC_LES on Sat, 20 February 2010 16:45
		Re: [GMCnet] Injection versus Carbs By: WD0AFQ on Sat, 20 February 2010 17:35

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