Q junk problem! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

d10s69c10 · 08-01-2008, 06:56 PM

alright took the truck out for a small ride to the gas station today noticed it was Lagging a bit so i took her home and gave her a look..

all and all im noticing my secondary isnt opening up when i floor the throttle...
the vacume diaphram is moving a little bit but thru all the room between pins its just not pulling the butterflys open.

its not stuck wich was a problem a few years ago..

do i need to go buy a new vacume pump and line or is there something im missing?

**john** · 08-01-2008, 07:22 PM

You have a Q jet w/vacuum secondaries which need to be under load to open.

heavy71chevy · 08-01-2008, 07:37 PM

agreed

Bus Ted Knuckle · 08-01-2008, 09:18 PM

clean your fuel filters, how long has it been since you did a tune up? You aren't likely to open your secondarys by reving it in park.

QKENUF4U · 08-01-2008, 09:47 PM

you already figurd it out with your statement "Q-JUNK" . they either work perfect or not at all. i HATE
Q-JUNKS and will never even try to ever use another one. i LOVE CARTERS/EDELBROCKS myself and have had nothing but good times with those carbs. i did like holleys but they take to much tuning to get perfect. JUST MY OPINION and EXPERIENCES

**special-K** · 08-01-2008, 10:36 PM

I think Quadrajets are great carbs.Especially when you understand how they work.They come on Chevys,so you know they are good.Chevys treat you right.
I`ve had and heard alot of trouble with Edelbrocks.
I know everyone has different experiences.

**Boog** · 08-01-2008, 10:52 PM

If it's good enough for the General then it's good enough for me. Power and mileage. Best of both worlds. And they shor do bellar when you stick yor foot in it!

Blazer1970 · 08-02-2008, 06:42 AM

As others have noted, the secondary air valve on a Quadra-Jet will never open when you are revving the engine in the driveway. The engine needs to be under a high load with open throttle (low vacuum condition) for the secondaries to open.

hgs_notes · 08-02-2008, 07:31 AM

Lag could be from lots of issues. The timing may be off, the accelerator pump might be bad, fuel filter plugged, old gas, choke adjustment and temp of the engine, etc. If this was a short trip and the engine was not warmed up, it will be doggie on hard acceleration.

You can test the vacuum secondary actuator by unconnecting the vacuum line, then push the plunger in, put a finger over the vacuum connector and letting go of the plunger. It should move a little then stop and hold. If it slides all the way back with your finger blocking the tube, the diaphram is bad. But I don't really think that's your problem.

**Boog** · 08-02-2008, 07:57 AM

Also if the choke valve is not completely open the secondary air valve cannot open. There is a small linkage behind the choke housing that rotates as the choke warms up. It effectively prevents you from WOT and dumping large amounts of gas into the engine until it is completely warmed up.

Blazer1970 · 08-03-2008, 06:47 AM

Quote:

Originally Posted by Boog

Also if the choke valve is not completely open the secondary air valve cannot open. There is a small linkage behind the choke housing that rotates as the choke warms up. It effectively prevents you from WOT and dumping large amounts of gas into the engine until it is completely warmed up.

Actually, the choke locks out the secondary butterflies, not the air valve but the effect is the same.

**Boog** · 08-03-2008, 10:36 AM

You are technically correct Tim, on some. On some, the linkage blocked the air valve from opening. I do not have one here to take a pic but seems like they were on the early 70s models. There were variations. May have been on my Olds. Anyway I believe our point is made.

08-01-2008, 06:56 PM	#1
d10s69c10 Built 4 Speed Join Date: May 2008 Location: Geneva FL Posts: 619	Q junk problem! alright took the truck out for a small ride to the gas station today noticed it was Lagging a bit so i took her home and gave her a look.. all and all im noticing my secondary isnt opening up when i floor the throttle... the vacume diaphram is moving a little bit but thru all the room between pins its just not pulling the butterflys open. its not stuck wich was a problem a few years ago.. do i need to go buy a new vacume pump and line or is there something im missing? __________________ 1969 C/10 Short Box: 496/T-56 in worx. "To Be Old And Wise, First You Must Be Young And Stupid"

08-01-2008, 07:22 PM	#2
john member #16 Join Date: Dec 1999 Location: Yuba City Ca. Posts: 3,618	Re: Q junk problem! You have a Q jet w/vacuum secondaries which need to be under load to open. __________________ john http://67-72chevytrucks.com/vboard/showgroups.php board vendors http://www.flickr.com/photos/1745471...7602865984234/

08-01-2008, 07:37 PM	#3
heavy71chevy Registered User Join Date: Apr 2007 Location: antreville, south carolina Posts: 873	Re: Q junk problem! agreed __________________ "Dixie Destroyer" 71 C10 LWB Fleet Future Blown Prostreet Monster

08-01-2008, 09:18 PM	#4
Bus Ted Knuckle Son of a gun Join Date: Jan 2007 Location: Hot Springs, Arkansas Posts: 1,636	Re: Q junk problem! clean your fuel filters, how long has it been since you did a tune up? You aren't likely to open your secondarys by reving it in park. __________________ Bill BEATERS ARE NEATER

08-01-2008, 09:47 PM	#5
QKENUF4U Senior Member Join Date: Jan 2005 Location: SUNNY WARM BIKE RIDING COTTONWOOD ARIZONA Posts: 2,097	Re: Q junk problem! you already figurd it out with your statement "Q-JUNK" . they either work perfect or not at all. i HATE Q-JUNKS and will never even try to ever use another one. i LOVE CARTERS/EDELBROCKS myself and have had nothing but good times with those carbs. i did like holleys but they take to much tuning to get perfect. JUST MY OPINION and EXPERIENCES

08-01-2008, 10:36 PM	#6
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,852	Re: Q junk problem! I think Quadrajets are great carbs.Especially when you understand how they work.They come on Chevys,so you know they are good.Chevys treat you right. I`ve had and heard alot of trouble with Edelbrocks. I know everyone has different experiences. __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~

08-01-2008, 10:52 PM	#7
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 13,458	Re: Q junk problem! If it's good enough for the General then it's good enough for me. Power and mileage. Best of both worlds. And they shor do bellar when you stick yor foot in it! __________________ 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

08-02-2008, 06:42 AM	#8
Blazer1970 Registered User Join Date: Dec 1999 Location: Old Mission, MI, USA Posts: 2,510	Re: Q junk problem! As others have noted, the secondary air valve on a Quadra-Jet will never open when you are revving the engine in the driveway. The engine needs to be under a high load with open throttle (low vacuum condition) for the secondaries to open. __________________ Tim Last edited by Blazer1970; 08-02-2008 at 06:43 AM. Reason: clarity

08-02-2008, 07:31 AM	#9
hgs_notes GEARHEAD Join Date: Aug 2003 Location: MN Posts: 6,126	Re: Q junk problem! Lag could be from lots of issues. The timing may be off, the accelerator pump might be bad, fuel filter plugged, old gas, choke adjustment and temp of the engine, etc. If this was a short trip and the engine was not warmed up, it will be doggie on hard acceleration. You can test the vacuum secondary actuator by unconnecting the vacuum line, then push the plunger in, put a finger over the vacuum connector and letting go of the plunger. It should move a little then stop and hold. If it slides all the way back with your finger blocking the tube, the diaphram is bad. But I don't really think that's your problem. __________________ If no one knows what you're doing, they can't tell you you're doing it wrong HG's Dream Car Build - Shelby Cobra Kit Build your own adjustable track bar 71 Long Fleet C/10 72 Jimmy 4x4 (Junkyard Jimmy) HG's Plow Truck '78 K35 Dually Bigass Farm Truck HG's thread of miscellaneous stuff

08-02-2008, 07:57 AM	#10
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 13,458	Re: Q junk problem! Also if the choke valve is not completely open the secondary air valve cannot open. There is a small linkage behind the choke housing that rotates as the choke warms up. It effectively prevents you from WOT and dumping large amounts of gas into the engine until it is completely warmed up. __________________ 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

08-03-2008, 10:36 AM	#12
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 13,458	Re: Q junk problem! You are technically correct Tim, on some. On some, the linkage blocked the air valve from opening. I do not have one here to take a pic but seems like they were on the early 70s models. There were variations. May have been on my Olds. Anyway I believe our point is made. __________________ 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



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