Got a Q-jet problem... - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**SOUTHERN917** · 03-05-2009, 07:56 PM

Yeah, I know..."all Q-jets are a problem" I'm gonna ask anyway. I did a basic rebuild on my 70 Q-jet, new gaskets,needle & seat, brass float, plunger, etc. Truck runs better than before, but now I have fuel leaking out front throttle bushings (both sides). What the he!! did I do? Carb is dry as a bone overnight. Did cleaning crud off well plugs "unseal" them? any suggestions would be appreciated.

JimKshortstep4x4 · 03-05-2009, 09:05 PM

Unless the needle valve is leaking the problem is probably the well plugs. It is a good practice to epoxie the well plugs when you have the carb apart.

I have had excellent service from Q-Jets so I like them.

Jim

1320tech · 03-05-2009, 09:13 PM

I like Q-jet carbs also for all around steet driving they are hard to beat I agree with jimkshortstep4x4 always use 2 part epoxy on well plugs and check throttle shaft bushings for wear a good carb shop is hard to find anymore but there are still places around that can rebush the throttle plate. this makes a huge differance if they are worn at all .

**SOUTHERN917** · 03-05-2009, 09:14 PM

If I take it apart to seal wells, will the gaskets reseal or will I need to replace them again?

**1970cstblazer** · 03-05-2009, 09:26 PM

If you are careful, you can reuse the gaskets.

Q-Jets are versatile, and very sophisticated carbs, but are only as good as the guy that builds them. I have built over 50 of them, and have used the rest, but still I always prefer the much maligned Q-Jet.

Bus Ted Knuckle · 03-05-2009, 10:05 PM

q-jets are great. Lets get that out of the way!

Well plugs will not leak on the exterior of the carb, they leak on the inside, down the intake. Well plugs do not leak as much as they are rumored to, but your sound like they might be. the "crud" that you cleaned off was probably someone else's JB weld. If they are leaking, fix it like the old time mechanics did: take a ball peen hammer and GENTLY tap the solder around the plug in order to flatten it. This will seal them much better than gooping on pucky that is not gasoline resistant. Do inspect the cross shafts for wear, but that will not cause it to leak either, it will cause it to run erratically, and lean.

Your shaft leaking problem is most likely caused by your float being set too high, allowing too much gas in the bowl. What is your carb number, and what did you set your float at? Alternatively, hanging the needle on the float backwards can cause the needle to jam in the seat, keeping it from sealing properly. Make sure your needle is hanging off the the end of the float arm that faces the radiator (not between the float and the cross arm that the needle hangs on). Finally, if you are careful you can reuse your gaskets.

**SOUTHERN917** · 03-05-2009, 10:21 PM

I love my Q-jet, I usually get replys like"get a holley" or "junk it". My # is 7040202, and I'll double check my measurements. Thanks for all the help, I'll keep you posted.

straitnate14 · 03-06-2009, 05:29 AM

Quote:

Originally Posted by SOUTHERN917

I love my Q-jet, I usually get replys like"get a holley" or "junk it". My # is 7040202, and I'll double check my measurements. Thanks for all the help, I'll keep you posted.

get a holley... (I had to)

67shortie · 03-06-2009, 06:44 AM

Quadrajets like a 1/4 to 3/16 float measurement taken at the high edge of the float to the bowl surface.

ChevLoRay · 03-06-2009, 07:56 AM

For what it's worth, I like my quadrajet, too. At the same time, I've never owned a Holley, unless it was on a Ford product I happened to own. But, it wasn't anything more than a stock Ford application and not a high-performance one. Carter has made the majority of carbs that I have used, but the Q-Jet was new from Edelbrock and ran out of the box w/o any adjustments needed, short of idle speed.

Skirkpat · 03-06-2009, 11:03 AM

If anyone tells you that a Quadrajet is not a good carb for a street driven / mild performance engine is not really who you should be discussing engine performance with, for all out high performance a Holley will slightly outperform them, but on the streets the Quad's hard to beat, Very tunable and great manners (And I am a guy who loves Holleys)!!!!

texanidiot25 · 03-06-2009, 01:01 PM

A well set Q-Jet whoops all for the street. Good MPG, fast throttle response, and plenty of smooth power.

stllookn · 03-06-2009, 04:26 PM

I have had problems with throttle shaft leakage on really old worn-out carbs...mostly 2-barrel Rochesters. The really good and careful rebuilders (that ain't me) will always measure the throttle shaft and bushings then replace the bushings. I usually just wing it and hope for the best. It has worked well so far but I did get bit once...LOL! It is a bit disheartening to see that gas leaking from the throttle shaft bushing!

**oldgold70c10** · 03-06-2009, 06:58 PM

Nothing beats a Q-jet. I've got one on my burb, my malibu, and will soon have one in my truck. Go out and find the S-A design book on Q-jet carbs. It was well worth the price and has a lot of advice on rebuilding, fixing leaks, rebushing the throttle shafts, and even performance tuning and modifications.

ratpackv8sonly · 03-06-2009, 08:02 PM

Yup love the Q-Jets myself. Will always have one on my 69 as long as I own it. FYI If you do go back through it an put back the epoxy just be careful to not use the fast setting JB-weld as it will soften op with the heat. Use the original 24 hour JB-Weld.

chipflyer · 03-06-2009, 09:59 PM

Another quadrajet fan here. If they were so bad GM wouldn't have used them on millions of engines for years, including 327's, 350's, 396, and 454 performance models. They are somewhat tricky for the average guy to work on but there are some great books and websites out there that cover them pretty well.
I bought Cliff Ruggles "How to rebuild and modify Quadrajet Carburetors" and it's an awesome book with lots of great info. I am currently going through a 72 truck carb and the mods in the book are supposed to really improve economy and performance. I would check the float level and reseal those main fuel passage plugs and try it again.

Here's a link to Cliffs quadrajet technical forum http://www.cliffshighperformance.com/simplemachinesforum/

Info from Lars Grimsrud (another quadrajet Guru). Great quadrajet info

Lugnut64052 · 03-06-2009, 10:08 PM

Quote:

Originally Posted by bus ted knuckle

q-jets are great. Lets get that out of the way!

Well plugs will not leak on the exterior of the carb, they leak on the inside, down the intake. Well plugs do not leak as much as they are rumored to, but your sound like they might be. The "crud" that you cleaned off was probably someone else's jb weld. If they are leaking, fix it like the old time mechanics did: Take a ball peen hammer and gently tap the solder around the plug in order to flatten it. This will seal them much better than gooping on pucky that is not gasoline resistant. Do inspect the cross shafts for wear, but that will not cause it to leak either, it will cause it to run erratically, and lean.

Your shaft leaking problem is most likely caused by your float being set too high, allowing too much gas in the bowl. What is your carb number, and what did you set your float at? Alternatively, hanging the needle on the float backwards can cause the needle to jam in the seat, keeping it from sealing properly. Make sure your needle is hanging off the the end of the float arm that faces the radiator (not between the float and the cross arm that the needle hangs on). Finally, if you are careful you can reuse your gaskets.

x2

**SOUTHERN917** · 03-07-2009, 04:05 PM

Well here's my update.... Went out last night to start in with all the helpful suggestions, and found...NO MORE LEAK... It started on the first crank, no pumping it up first. I guess the old Chevy fairy had mercy on me

So with this little bit of luck, I'm gotta go get a lottery ticket!

Thanks again for all the suggestions, I'll file them just in case!

03-05-2009, 07:56 PM	#1
SOUTHERN917 Wrench Wench Join Date: Apr 2008 Location: HERRIN, IL Posts: 93	Got a Q-jet problem... Yeah, I know..."all Q-jets are a problem" I'm gonna ask anyway. I did a basic rebuild on my 70 Q-jet, new gaskets,needle & seat, brass float, plunger, etc. Truck runs better than before, but now I have fuel leaking out front throttle bushings (both sides). What the he!! did I do? Carb is dry as a bone overnight. Did cleaning crud off well plugs "unseal" them? any suggestions would be appreciated. __________________ If everyone had good taste, who would buy all the FORDS? Women join us!! BUSTED KNUCKLE BABES "Face it girls, I'm older and have better insurance" -Fried green tomatoes

03-05-2009, 09:05 PM	#2
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	Re: Got a Q-jet problem... Unless the needle valve is leaking the problem is probably the well plugs. It is a good practice to epoxie the well plugs when you have the carb apart. I have had excellent service from Q-Jets so I like them. Jim __________________ 1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC

03-05-2009, 09:13 PM	#3
1320tech Registered User Join Date: Jun 2008 Location: newparis ohio Posts: 201	Re: Got a Q-jet problem... I like Q-jet carbs also for all around steet driving they are hard to beat I agree with jimkshortstep4x4 always use 2 part epoxy on well plugs and check throttle shaft bushings for wear a good carb shop is hard to find anymore but there are still places around that can rebush the throttle plate. this makes a huge differance if they are worn at all .

03-05-2009, 09:14 PM	#4
SOUTHERN917 Wrench Wench Join Date: Apr 2008 Location: HERRIN, IL Posts: 93	Re: Got a Q-jet problem... If I take it apart to seal wells, will the gaskets reseal or will I need to replace them again? __________________ If everyone had good taste, who would buy all the FORDS? Women join us!! BUSTED KNUCKLE BABES "Face it girls, I'm older and have better insurance" -Fried green tomatoes

03-05-2009, 09:26 PM	#5
1970cstblazer All stock and staying that way Join Date: Jul 2003 Location: Elkland, PA Posts: 1,415	Re: Got a Q-jet problem... If you are careful, you can reuse the gaskets. Q-Jets are versatile, and very sophisticated carbs, but are only as good as the guy that builds them. I have built over 50 of them, and have used the rest, but still I always prefer the much maligned Q-Jet. __________________ 1970 K/5 Blazer CST 4WD, Bronze, 93k ACT. miles, 350, 4 speed, positraction, 16.5" x 8.25" wheel option, tilt, tach, vacuum, AM/FM, manual throttle...Dad ordered and purchased new 4/70. Currently frame off restoration in progress... 1972 Cheyenne Super 20 2WD, DK Blue/White, 90K ACT. miles, 402, TH400, 4.10 open, tilt, tach, vacuum, A/C, AM/FM, manual throttle.. A mostly original paint never rusted Texas survivor... 2017 Sierra 1500 SLT 4WD, Black, 41k miles, 5.3, 6L80E, 3.42 LS, 20" polished wheels, everything but moonroof and 6.2... 2019 Canyon SLT 4WD, White, 60k miles, 3.6, 8L45, 3.23 LS, 18" wheels

03-05-2009, 10:05 PM	#6
Bus Ted Knuckle Son of a gun Join Date: Jan 2007 Location: Hot Springs, Arkansas Posts: 1,636	Re: Got a Q-jet problem... q-jets are great. Lets get that out of the way! Well plugs will not leak on the exterior of the carb, they leak on the inside, down the intake. Well plugs do not leak as much as they are rumored to, but your sound like they might be. the "crud" that you cleaned off was probably someone else's JB weld. If they are leaking, fix it like the old time mechanics did: take a ball peen hammer and GENTLY tap the solder around the plug in order to flatten it. This will seal them much better than gooping on pucky that is not gasoline resistant. Do inspect the cross shafts for wear, but that will not cause it to leak either, it will cause it to run erratically, and lean. Your shaft leaking problem is most likely caused by your float being set too high, allowing too much gas in the bowl. What is your carb number, and what did you set your float at? Alternatively, hanging the needle on the float backwards can cause the needle to jam in the seat, keeping it from sealing properly. Make sure your needle is hanging off the the end of the float arm that faces the radiator (not between the float and the cross arm that the needle hangs on). Finally, if you are careful you can reuse your gaskets. __________________ Bill BEATERS ARE NEATER Last edited by Bus Ted Knuckle; 03-05-2009 at 10:10 PM. Reason: fat fingers

03-05-2009, 10:21 PM	#7
SOUTHERN917 Wrench Wench Join Date: Apr 2008 Location: HERRIN, IL Posts: 93	Re: Got a Q-jet problem... I love my Q-jet, I usually get replys like"get a holley" or "junk it". My # is 7040202, and I'll double check my measurements. Thanks for all the help, I'll keep you posted. __________________ If everyone had good taste, who would buy all the FORDS? Women join us!! BUSTED KNUCKLE BABES "Face it girls, I'm older and have better insurance" -Fried green tomatoes

03-06-2009, 06:44 AM	#9
67shortie Green club Join Date: May 2002 Location: Central CA Posts: 1,059	Re: Got a Q-jet problem... Quadrajets like a 1/4 to 3/16 float measurement taken at the high edge of the float to the bowl surface. __________________ 71 short/fleet ECE 4/6 drop, LQ4/700r4/3.42 gears 70 SS396 Chevelle 427/200-4R/3.73posi 61 Lincoln Continental, black on black Son you are going to drive me to drinkin if you don't stop drivin that hot rod lincoln

03-06-2009, 07:56 AM	#10
ChevLoRay Old Skool Club Join Date: Jun 2001 Location: Benton, AR "The Heart of Arkansas" Posts: 10,880	Re: Got a Q-jet problem... For what it's worth, I like my quadrajet, too. At the same time, I've never owned a Holley, unless it was on a Ford product I happened to own. But, it wasn't anything more than a stock Ford application and not a high-performance one. Carter has made the majority of carbs that I have used, but the Q-Jet was new from Edelbrock and ran out of the box w/o any adjustments needed, short of idle speed. __________________ Member Nr. 2770 '96 GMC Sportside; 4.3/SLT - Daily driven....constantly needs washed. '69 C-10 SWB; 350/TH400 - in limbo The older I get, the better I was.

03-06-2009, 11:03 AM	#11
Skirkpat Registered User Join Date: Dec 2008 Location: K.C. Missouri Posts: 1,024	Re: Got a Q-jet problem... If anyone tells you that a Quadrajet is not a good carb for a street driven / mild performance engine is not really who you should be discussing engine performance with, for all out high performance a Holley will slightly outperform them, but on the streets the Quad's hard to beat, Very tunable and great manners (And I am a guy who loves Holleys)!!!!

03-06-2009, 01:01 PM	#12
texanidiot25 Eat My Rust Join Date: Jan 2007 Location: Cypress, Texas Posts: 3,362	Re: Got a Q-jet problem... A well set Q-Jet whoops all for the street. Good MPG, fast throttle response, and plenty of smooth power.

03-06-2009, 04:26 PM	#13
stllookn Saving 1 truck at a time! Join Date: Aug 2001 Location: Kent, WA Posts: 6,465	Re: Got a Q-jet problem... I have had problems with throttle shaft leakage on really old worn-out carbs...mostly 2-barrel Rochesters. The really good and careful rebuilders (that ain't me) will always measure the throttle shaft and bushings then replace the bushings. I usually just wing it and hope for the best. It has worked well so far but I did get bit once...LOL! It is a bit disheartening to see that gas leaking from the throttle shaft bushing! __________________ '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)

03-06-2009, 06:58 PM	#14
oldgold70c10 Who's got steelies? Join Date: Feb 2006 Location: Morrison, Oklahoma Posts: 1,026	Re: Got a Q-jet problem... Nothing beats a Q-jet. I've got one on my burb, my malibu, and will soon have one in my truck. Go out and find the S-A design book on Q-jet carbs. It was well worth the price and has a lot of advice on rebuilding, fixing leaks, rebushing the throttle shafts, and even performance tuning and modifications. __________________ 1969 C10 LWB W/ 250 I6 & 3spd 1970 C10 with '67 small window cab, 68 front end, blue; 305/TH350, 3.08 limited slip rear end, manual brakes, power steering; & 4-wheel drums-My daily driver. 1975 Chevelle Malibu Classic Coupe 350/th350 mint green 1970 C20 Suburban 350/700R4 4.10 gearing green & white 1978 Big 10 Silverado 350/th350, working ac, 2 tone blue-My summer daily driver 1983 GMC 1500 Sierra 305/SM465 2.73 rear end How to add a trip odometer to your 67-72 stock speedometer How to rebuild your Q-Jet My Truck Page My Youtube Channel

03-06-2009, 08:02 PM	#15
ratpackv8sonly Registered User Join Date: Mar 2008 Location: Las Cruces New Mexico Posts: 214	Re: Got a Q-jet problem... Yup love the Q-Jets myself. Will always have one on my 69 as long as I own it. FYI If you do go back through it an put back the epoxy just be careful to not use the fast setting JB-weld as it will soften op with the heat. Use the original 24 hour JB-Weld.

03-06-2009, 09:59 PM	#16
chipflyer Registered User Join Date: May 2004 Location: Topeka, Ks Posts: 2,293	Re: Got a Q-jet problem... Another quadrajet fan here. If they were so bad GM wouldn't have used them on millions of engines for years, including 327's, 350's, 396, and 454 performance models. They are somewhat tricky for the average guy to work on but there are some great books and websites out there that cover them pretty well. I bought Cliff Ruggles "How to rebuild and modify Quadrajet Carburetors" and it's an awesome book with lots of great info. I am currently going through a 72 truck carb and the mods in the book are supposed to really improve economy and performance. I would check the float level and reseal those main fuel passage plugs and try it again. Here's a link to Cliffs quadrajet technical forum http://www.cliffshighperformance.com/simplemachinesforum/ Info from Lars Grimsrud (another quadrajet Guru). Great quadrajet info __________________ I'm not a pessimist, I'm just optimistic that bad things are going to happen. 1971 Cheyenne Super K10 - tilt, cruise, air, am/fm, tow hooks, factory buckets! 1986 Jeep J10 pickup, - 5.3L Vortec with 4L60e and NP241.



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03-07-2009, 04:05 PM	#18
SOUTHERN917 Wrench Wench Join Date: Apr 2008 Location: HERRIN, IL Posts: 93	Re: Got a Q-jet problem... Well here's my update.... Went out last night to start in with all the helpful suggestions, and found...NO MORE LEAK... It started on the first crank, no pumping it up first. I guess the old Chevy fairy had mercy on me So with this little bit of luck, I'm gotta go get a lottery ticket! Thanks again for all the suggestions, I'll file them just in case! __________________ If everyone had good taste, who would buy all the FORDS? Women join us!! BUSTED KNUCKLE BABES "Face it girls, I'm older and have better insurance" -Fried green tomatoes

Register or Log In To remove these advertisements.