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Re: Jet changes-tell me your thoughts
[Re: Dunnuck Racing]
#371875
07/10/09 07:58 PM
07/10/09 07:58 PM
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Joined: Jan 2003
Posts: 4,085
Indiana
W5Duster436
master
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master
Joined: Jan 2003
Posts: 4,085
Indiana
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I have the same Q-950-AN with the 78/86's. I am waiting for an LM-1 to diagnose it. I did change the primaries to 76's but I know it's way too fat as it struggles to hit 7200 rpm. This is a 340 w/ 275 @.050 solid. street driven so don't really want to remove the PV. I am guessing I'll need to run that same 73/78 type when I can finally check it out with a meter.
'70 Duster - SDSS 436 W5 4spd (Gone)
'71 Dodge D100
'70 Dodge W100
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Re: Jet changes-tell me your thoughts
[Re: VernMotor]
#371876
07/10/09 08:04 PM
07/10/09 08:04 PM
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Joined: Jan 2005
Posts: 1,163
Newark, OH
Hunted Duck
super stock
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super stock
Joined: Jan 2005
Posts: 1,163
Newark, OH
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Quote:
My car changes in ET too much for me..from good to bad air..2000 ft to 4000 ft..7.00s to 7.teens
so I thought I would lean it up a touch.Now I thought the jets in the carb was what it came with. Had carb 2 years now and I have change them a flew times.But I open it up tonight and they are not. Carb is a QF 850 it came with 76-84 with PV .so the paper work I got says anyway?
It has 74-79 in it and tonight I change to 73-78. you think I am too far off base with these from what it came with ?
Jamie what air bleeds are you running? Sounds like you may need to change the high side bleed to me.
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Re: Jet changes-tell me your thoughts
[Re: VernMotor]
#371880
07/10/09 09:39 PM
07/10/09 09:39 PM
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Joined: May 2007
Posts: 1,443
Maryland
Dads426
pro stock
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pro stock
Joined: May 2007
Posts: 1,443
Maryland
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Check your vacuum at idle in gear. Power valve value should be numerically lower or it will stay open at idle and affect driveability. An old-timer that I respected told me to run a little on the rich side as it will even out the changes in weather (lean mixtures tend to be more sensitive); our old 440 w/an 850 DP ran 82/88 jets with a 4.5 PV for an A/F ratio of 12.5-1 on gas. I remember in the Junior Dragster (Nitro Fish car) running a little rich worked pretty well.
2012 422 Allstars NSS Champion
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Re: Jet changes-tell me your thoughts
[Re: Dads426]
#371881
07/10/09 09:41 PM
07/10/09 09:41 PM
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Joined: Jan 2003
Posts: 32,394
Quicktree
I Win
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Quote:
Check your vacuum at idle in gear. Power valve value should be numerically lower or it will stay open at idle and affect driveability. An old-timer that I respected told me to run a little on the rich side as it will even out the changes in weather (lean mixtures tend to be more sensitive); our old 440 w/an 850 DP ran 82/88 jets with a 4.5 PV for an A/F ratio of 12.5-1 on gas. I remember in the Junior Dragster (Nitro Fish car) running a little rich worked pretty well.
not really, running it rich will cause a huge gap between good air and bad. 
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Re: Jet changes-tell me your thoughts
[Re: VernMotor]
#371883
07/10/09 10:05 PM
07/10/09 10:05 PM
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Joined: Jan 2003
Posts: 32,394
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Quote:
It has 4.5 PV in it.. Not sure why I have jets that lean..74-79 has been good to me..Just seems a touch to rich..But I agree that I should not be jet'ed down that much?
why do you think it's rich?
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Re: Jet changes-tell me your thoughts
[Re: Dads426]
#371885
07/10/09 10:10 PM
07/10/09 10:10 PM
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Joined: Jan 2003
Posts: 32,394
Quicktree
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Quote:
Quote:
not really, running it rich will cause a huge gap between good air and bad.
How so? It seems that the engine will have more leeway to run safely and in an acceptable A/F mixture zone (due to weather changes) when on the rich side than when lean.
because when it's hot and humid and your running rich you can't burn the fuel- slowing it down. then when the air is better and the humidity comes down the car speeds up. if you want to run consistent you run lean.
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Re: Jet changes-tell me your thoughts
[Re: VernMotor]
#371887
07/10/09 10:15 PM
07/10/09 10:15 PM
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Joined: Jan 2003
Posts: 32,394
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Quote:
Just because it pick up with good air..thats all?
plugs do not look lean by no mean.maybe a touch dark..but not bad. I can dial the car the way it is.we have won a flew races..I just picking at it to make it better. most of our day start out in the 3500 DA and end up 1800 da.. car out of the box will run 7.10-7.11 by the night over with we are running 7.05 7.04 ..I have seen 4000 da out of the box run about 7.14-7.15 and seen the air change to 1500-1200 da and car runs run 7.02-7.03
when was the last time you cleaned and blew out the carb? does sound like it's rich. maybe it has something to do with the way it's set up. also check to see if the jets have been drilled. try going down on jets one or two sizes to see what happens. it may slow the car a little but make it more consistent.
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Re: Jet changes-tell me your thoughts
[Re: Dads426]
#371890
07/10/09 10:25 PM
07/10/09 10:25 PM
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Joined: Jan 2003
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Quote:
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because when it's hot and humid and your running rich you can't burn the fuel- slowing it down. then when the air is better and the humidity comes down the car speeds up. if you want to run consistent you run lean.
How lean? 12/1; 13/1; 14/1? What is an acceptable range for making power, being consistent and not hurting parts?
forget the af readings, yes it may hurt power a little. I doubt you could get lean enough to hurt any parts.
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Re: Jet changes-tell me your thoughts
[Re: Hunted Duck]
#371892
07/10/09 10:50 PM
07/10/09 10:50 PM
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Joined: Jan 2003
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Quote:
Jamie I would take the high side air bleed to .035 and leave the jets alone. You said you had .033 in it now, right? That will lean it out alittle. JMO 
very little
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