tuning dual carbs? - Team Camaro Tech
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post #1 of 8 (permalink) Old Mar 24th, 11, 04:16 PM Thread Starter
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Brian
 
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tuning dual carbs?

my dad's friend has a blown 383 with a 6-71 s/c....with 2 650 quick fuel carbs i think?

he's having a problem tuning them right and has called quick fuel's tech line just to talk to an idiot...not sure if he has called back yet to talk to someone else there...

i'm just trying to help since he painted my new front bumper on my s10 for me...lol

what he says it does is idle fine for 20 seconds then immediately runs rich, black smoke out the exhaust, and even leaves exhaust marks all over the ground...and he just can't tune it right...?

i think he said he had 66 size jets? big fuel line and big fuel pump...lol...not sure what size...and also he has plugged the power valves and/or unplugged them i don't know...sorry carbs are chinese to me...so nevermind my ignorance. lol

any help would be greatly appreciated. thank you!!

Brian
MY RIDE

01 S10 Xtreme 2/3 drop, BUILT 4.3L v6, 5spd
DADS RIDE
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post #2 of 8 (permalink) Old Mar 24th, 11, 05:37 PM
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Cory
 
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Re: tuning dual carbs?

if this is a street car, take the power valve plugs out, install some 6.5's, run the car, hook up vaccum gauge and start from there. set the timing or check it again.

68 with a 505cid
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post #3 of 8 (permalink) Old Mar 24th, 11, 06:29 PM Thread Starter
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Brian
 
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Re: tuning dual carbs?

Pretty sure it's just a race car, pushing 600+ hp but since it's so incredibly nice and clean it could be just a street/show car i don't know...

I will find out more info and post back...which i probably should have done to begin with...lol thanks!

Brian
MY RIDE

01 S10 Xtreme 2/3 drop, BUILT 4.3L v6, 5spd
DADS RIDE
69 Camaro 500+ hp 355, t400, currie ford 9inch 4.56 gears, 100 shot
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post #4 of 8 (permalink) Old Mar 24th, 11, 07:02 PM
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george
 
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Re: tuning dual carbs?

Quote:
Originally Posted by joyride_ View Post
my dad's friend has a blown 383 with a 6-71 s/c....with 2 650 quick fuel carbs i think?

he's having a problem tuning them right and has called quick fuel's tech line just to talk to an idiot...not sure if he has called back yet to talk to someone else there...

i'm just trying to help since he painted my new front bumper on my s10 for me...lol

what he says it does is idle fine for 20 seconds then immediately runs rich, black smoke out the exhaust, and even leaves exhaust marks all over the ground...and he just can't tune it right...?

i think he said he had 66 size jets? big fuel line and big fuel pump...lol...not sure what size...and also he has plugged the power valves and/or unplugged them i don't know...sorry carbs are chinese to me...so nevermind my ignorance. lol

any help would be greatly appreciated. thank you!!
Brian...hard to tune a carb if the ignition system is not up to snuff and the initial timing is off for the given application.Would be nice to know what is going on there.
The obvious comes to mind.The dual carbs have the float levels set correct,the pump pressure is regulated as to not overpower the needle and seat,the throttle plates are set as to not yank on the transition slots,the idle mixture screws are functioning and idle emulsified mix responds accordingly,low speed air bleeds are free and clear,bowl vents can breathe etc.
The main jet size and pv selection will have no effect on your idle a/f unless your yanking on the boosters.
At this point..I would take that 20 second window and get over the carbs and look for fuel pullover..beit boosters or discharge nozzles.If your not seeing raw fuel atop,suspect an internal leak path by a gasket.
To summarize..square off the transition slots and baseline the idle mixture screws 1/2 to 3/4 turn out off seat.This is a ballpark setting for a 2x4 application.If alls correct..you should be able to alter idle rpm and a/f ratio with mixture screw adjustments only.
Not a lot to go on with your limited info^..just food for thought for now.
Good luck and happy tuning.

George
68 Camaro
8-71 blown 461 Rat on E-85

Last edited by fatblock; Mar 24th, 11 at 07:33 PM.
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post #5 of 8 (permalink) Old Mar 24th, 11, 10:17 PM
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darrell
 
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Re: tuning dual carbs?

fatblok has it check all that and if all fails --it might be that the butterflys might need to be drilled but need alots more info before assuming that
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post #6 of 8 (permalink) Old Mar 30th, 11, 10:45 AM Thread Starter
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Brian
 
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Re: tuning dual carbs?

Going to his house today shortly so I'll let em' know what you guys offered up for advice and see what he has done/hasn't and get back to you guys with more info! Thanks for all the help Over and out! lol

Brian
MY RIDE

01 S10 Xtreme 2/3 drop, BUILT 4.3L v6, 5spd
DADS RIDE
69 Camaro 500+ hp 355, t400, currie ford 9inch 4.56 gears, 100 shot
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post #7 of 8 (permalink) Old Mar 30th, 11, 12:39 PM
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Steps
 
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Re: tuning dual carbs?

Quote:
hard to tune a carb if the ignition system is not up to snuff and the initial timing is off
Quote:
Pretty sure it's just a race car, pushing 600+ hp
In that case most proberly has a fixed dizzy.,,and with a cam to meet that sort of HP idle speed could require to be up around 1200 rpms to meet min air fuel requirements from each carb idle circuits.

Quote:
it might be that the butterflys might need to be drilled but need alots more info before assuming that
Dual carbs there will be no shortage of air supply I sec s adjusted correct

Quote:
beit boosters or discharge nozzles.If your not seeing raw fuel atop,suspect an internal leak path by a gasket.
Gaskets a very common mistake when modding carbs at home....metering and base gaskets.

My Spelling is not incorrect...it is creative

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post #8 of 8 (permalink) Old Mar 31st, 11, 11:51 AM Thread Starter
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Brian
 
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Re: tuning dual carbs?

I forgot to update last night. Sorry guys...The problem turned out to be a simple one. Something they noticed by accident I guess? The accelerator pump was stuck open on one of them..? I don't know anything about carbs but I guess that meant that it was just letting gas flow right in?

So he apparently has it figured out, but wouldn't fire it up yesterday. Damn rain and WA weather here!

Once again though, thank you for your guys help. Appreciate it but I guess I didn't have a chance to share your info to him.

Brian
MY RIDE

01 S10 Xtreme 2/3 drop, BUILT 4.3L v6, 5spd
DADS RIDE
69 Camaro 500+ hp 355, t400, currie ford 9inch 4.56 gears, 100 shot
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