Need some quadrajet help... - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**FRENCHBLUE72** · 01-09-2007, 09:07 PM

Can anyone tell me what this little vaccum looking thing is for and do I need to run a vaccum line to it??? Any help would be great.... btw I have not ran this carb before..... Just need some help before I fire it up..

stllookn · 01-09-2007, 09:39 PM

Lance, What is the carb number. If that is on the right side of the carb on the forward end it is probably the vacuum break assembly (choke pull-off). It is hard to see from the pictures...but maybe that is my computer screen.

On further review...I reserve judgement as to it's EXACT method of function during the start or run cycle...LOL!

Hook it up to a vacuum line for certain. The spec. on it should be 10-12 inches of vaccum will hold the choke open...if it leaks down it will need to be replaced.

**Boog** · 01-09-2007, 09:46 PM

No, it's not just your puter screen. We've got a serious blurrrrrrrrr goin on here.

**FRENCHBLUE72** · 01-09-2007, 10:05 PM

Still have not figured out the new camera..... I can get the carb # wensday as the truck is not at my house right now...

**FRENCHBLUE72** · 01-09-2007, 10:06 PM

I dont run a choke on this truck,was wondering if it had something to do with the secondaries..

**Boog** · 01-09-2007, 10:13 PM

Very well could be. Is there a vacumn port at the rear of the carb the right size for a hose to attach this vacumn pod? Seems like my old 85s had this on them.

red71cheyenne · 01-09-2007, 10:42 PM

Its on the passenger side right? If so, it is the secondaries. Vacuum line goes up to one of the ports on the front I think. Can't remember now where mine plugged in...

FarmTruk · 01-09-2007, 11:39 PM

I know diddly squat about Q-jets, but heres a link to Q-jet manual scanned on-line. The pic below was copied from there. Good luck...

Linky...http://www.tocmp.com/manuals/Carbs/R...QJet/index.htm

cooters · 01-11-2007, 09:03 PM

the vacuum piece is a secondary air valve damper which will not allow the secondary air door to open under regular driving which would cause it to bog. Also slows the opening of the valve when you hit the throttle hard to prevent bog. I love these carbs

*rage'nrat638* · 01-11-2007, 09:12 PM

you got it brother..should hook up right the in the rear if the carb.
if thats on a 67-72 truck that looks like a newer vintage carb. heres a few pictures of the one i converted to electric choke

the last picture shows it hooked up new to the power brake vacuum fitting in the rear

01-09-2007, 09:07 PM	#1
FRENCHBLUE72 PROJECT 7DEUCE Join Date: Dec 2002 Location: GRANTS PASS OR Posts: 21,608	Need some quadrajet help... Can anyone tell me what this little vaccum looking thing is for and do I need to run a vaccum line to it??? Any help would be great.... btw I have not ran this carb before..... Just need some help before I fire it up.. Attached Images __________________ GO BIG GREEN GO DUCKS MEMBER #6377 72 k-5 daily driver 6'' lift 35'' 350-350-205 slowly getting rust free. Project "7DEUCE" check out my build http://67-72chevytrucks.com/vboard/s...d.php?t=267665 Tim Powell..R.I.P EastSideLowlife..... R.I.P..

01-09-2007, 09:39 PM	#2
stllookn Saving 1 truck at a time! Join Date: Aug 2001 Location: Kent, WA Posts: 6,465	Re: Need some quadrajet help... Lance, What is the carb number. If that is on the right side of the carb on the forward end it is probably the vacuum break assembly (choke pull-off). It is hard to see from the pictures...but maybe that is my computer screen. On further review...I reserve judgement as to it's EXACT method of function during the start or run cycle...LOL! Hook it up to a vacuum line for certain. The spec. on it should be 10-12 inches of vaccum will hold the choke open...if it leaks down it will need to be replaced. __________________ '68 C20 Longhorn 50th Anniversary 400/TH400 '68 C20 Longhorn 50th Anniversary 468/TH400w/buckets '72 C20 Halfhorn (Longhorn w/o cab and front clip) '69 Flxible Cruiser (look up ugly in the dictionary) Last edited by stllookn; 01-09-2007 at 09:49 PM.

01-09-2007, 09:46 PM	#3
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 13,190	Re: Need some quadrajet help... No, it's not just your puter screen. We've got a serious blurrrrrrrrr goin on here. __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross

01-09-2007, 10:05 PM	#4
FRENCHBLUE72 PROJECT 7DEUCE Join Date: Dec 2002 Location: GRANTS PASS OR Posts: 21,608	Re: Need some quadrajet help... Still have not figured out the new camera..... I can get the carb # wensday as the truck is not at my house right now... __________________ GO BIG GREEN GO DUCKS MEMBER #6377 72 k-5 daily driver 6'' lift 35'' 350-350-205 slowly getting rust free. Project "7DEUCE" check out my build http://67-72chevytrucks.com/vboard/s...d.php?t=267665 Tim Powell..R.I.P EastSideLowlife..... R.I.P..

01-09-2007, 10:06 PM	#5
FRENCHBLUE72 PROJECT 7DEUCE Join Date: Dec 2002 Location: GRANTS PASS OR Posts: 21,608	Re: Need some quadrajet help... I dont run a choke on this truck,was wondering if it had something to do with the secondaries.. __________________ GO BIG GREEN GO DUCKS MEMBER #6377 72 k-5 daily driver 6'' lift 35'' 350-350-205 slowly getting rust free. Project "7DEUCE" check out my build http://67-72chevytrucks.com/vboard/s...d.php?t=267665 Tim Powell..R.I.P EastSideLowlife..... R.I.P..

01-09-2007, 10:13 PM	#6
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 13,190	Re: Need some quadrajet help... Very well could be. Is there a vacumn port at the rear of the carb the right size for a hose to attach this vacumn pod? Seems like my old 85s had this on them. __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross

01-09-2007, 10:42 PM	#7
red71cheyenne Back in the sticks Join Date: Jan 2001 Location: Fordland, MO Posts: 3,188	Re: Need some quadrajet help... Its on the passenger side right? If so, it is the secondaries. Vacuum line goes up to one of the ports on the front I think. Can't remember now where mine plugged in... __________________ 1971 Cheyenne C-10 w/700R4 and Tuned Port Injection 1969 K5 Blazer w/Tuned Port 2010 2SS/RS Flaming Orange Camaro 2011 K1500 Suburban 2014 K1500 Pickup 2008 Nissan Altima? The wifes' hoopty

01-09-2007, 11:39 PM	#8
FarmTruk In Memoriam... Join Date: Nov 2006 Location: Wallburg, NC Posts: 1,216	Re: Need some quadrajet help... I know diddly squat about Q-jets, but heres a link to Q-jet manual scanned on-line. The pic below was copied from there. Good luck... Linky...http://www.tocmp.com/manuals/Carbs/R...QJet/index.htm Attached Images __________________ '68 C10 SWB 307ci 2BBL *FarmTruk Pics Here* *"You know, doing what is right is easy. The problem is knowing what is right."*

01-11-2007, 09:03 PM	#9
cooters Senior Member Join Date: Oct 2006 Location: Edmonton Alberta Posts: 458	Re: Need some quadrajet help... the vacuum piece is a secondary air valve damper which will not allow the secondary air door to open under regular driving which would cause it to bog. Also slows the opening of the valve when you hit the throttle hard to prevent bog. I love these carbs

01-11-2007, 09:12 PM	#10
rage'nrat638 Account Suspended Join Date: Mar 2003 Location: THE FALL GUY CHICAGO IL Posts: 5,883	Re: Need some quadrajet help... you got it brother..should hook up right the in the rear if the carb. if thats on a 67-72 truck that looks like a newer vintage carb. heres a few pictures of the one i converted to electric choke the last picture shows it hooked up new to the power brake vacuum fitting in the rear Last edited by rage'nrat638; 07-12-2007 at 06:59 AM.



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