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#1 |
Registered User
Join Date: Jun 2014
Location: CO
Posts: 738
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Rebuilding Q-jet
I have been tearing apart my q-jet because of strong smell of gas when driving. Well when I took top plate of Q-jet off there was a broken pencil tip in the top of the vent tube??????? Some kind of Q-jet tuning I have never heard off LOL. I was also surprised to see threaded bolts(why would they be there, see pic) on either side of carb. Every time I open a q-jet I find interesting things that have been done to them. Anyway I think I inhaled to much carb cleaner fumes since I don't remember what is the base setting for idle mixture screws on a 4 barrel Q-jet. Do most people do 2 1/2 turns or 3 1/2 turns from bottomed out? On my 79 the idle screws were all the way closed down and with that pencil stuck in vent tube I am surprised the truck even ran down the road. My dad said this carb came from Advance auto and so that might explain why it was so beat up.
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79 Chevy 2wd BIG10 350 TH400 |
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#2 |
Registered User
Join Date: Feb 2005
Location: Saskatoon, SK
Posts: 97
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Re: Rebuilding Q-jet
The one on the outside is for idle speed. It's really just an adjustable stopper for the throttle body
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#3 |
Registered User
Join Date: Jun 2014
Location: CO
Posts: 738
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Re: Rebuilding Q-jet
Yeah not the idle speed adjuster just below it you can see a darker round circle inside the carb body. That is the screw that was placed in the bowl right there, you can actually see some threads poking out of the hole.
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79 Chevy 2wd BIG10 350 TH400 |
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#4 |
Registered User
Join Date: Feb 2005
Location: Saskatoon, SK
Posts: 97
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Re: Rebuilding Q-jet
Oh I see it now. That's weird. Maybe someones attempt to straighten out some warpage?
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#5 |
Registered User
Join Date: Apr 2007
Location: Birmingham AL
Posts: 255
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Re: Rebuilding Q-jet
That hole that the screw is stuck in is part of the idle air bypass system used on some Q-jets.
Make sure you put that secondary vent tube back in the hole it fell out of.
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Stock 75 C10 step side. 350 2 BBL, 350 trans. 150K miles. Last edited by ron350; 05-16-2016 at 07:05 PM. |
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