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Topic: 1979 L48 Quadrajet rebuild

in Forum: C3 Fuel, Emission Control, and Exhaust Systems

1979 L48 Quadrajet rebuild

Posted: 1/2/15 6:38pm Message 1 of 12
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taylors, SC - USA
Joined: 12/7/2014
Posts: 3
Vette(s): 1979 Corvette Dark Green all original 60,000 miles
I'm looking to rebuild the Quadrajet carb on my 1979 L48. I see so many places to buy the rebuild kits and the prices range from $27 to $75. I want to do this right the first time with a quality kit. Where can I find a rebuild kit that has quality parts? The carb has 60K miles. Will the new rebuild kits allow for the use of 10% ethanol gas. I have been using pure gas. Just wondering.

Thanks for all responses.

Phil


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Re: 1979 L48 Quadrajet rebuild

Posted: 1/2/15 8:29pm Message 2 of 12
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Duncanville, TX - USA
Joined: 11/8/2003
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas
If you have a NAPA auto parts place close, get the kit from them, and get a new float, also. You'll need the carb number to get the correct kit. You can find the Quadrajet ID number on the vertical edge of the carb, driver side rear.
 Most any kits these days will be ethanol resistant.



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Re: 1979 L48 Quadrajet rebuild

Posted: 1/3/15 8:55am Message 3 of 12
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WEST SENECA, NY - USA
Joined: 12/3/2001
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Vette(s): 1981 Blue Ice Met. w/pearl ghost flames TKO500 5speed. LS1 Swap 3.45 Dana 44.
Being a common issue with Rochester carbs, especially 4 spd. cars you might want to also check your primary throttle shaft for slop in it. If you grab the throttle linkage where the throttle cable goes to, try to move it forward, backward, up n down. If there is excessive play you'll want to do or have a bushing kit installed. Otherwise you'll have a vacuum leak there and you'll never get a solid carb adjustment after a rebuild. 
Another thing to do is use a straight edge on all the flat mating surfaces to make sure there is no major warpage. 




GEN III 5.7L "LS6" Engine swap
TKO500 5 spd.
3.54 Dana 44
'69 "N11" Sidepipes
Borgeson Steering Box
Born 8/1981
Sequence #3975




Click here to see more pics of my Vette on CarDomain.


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Re: 1979 L48 Quadrajet rebuild

Posted: 1/4/15 11:04pm Message 4 of 12
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Vancouver, WA - USA
Joined: 8/25/2005
Posts: 869
Vette(s): 1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.
I had really good luck with Cliff's High Performance.  Their kits are designed to work with today's ethanol fuels and they are not as generic as the parts house kits - more closely matched to your q-jet's model number.  As Sarge mentions, you should definitely think about re-bushing the primary throttle shaft.  Cliff's has the kits for doing that and I think they're also available on e-bay.  


Cliff also has a good book on rebuilding q-jets.  I used it along with Doug Roe's book on Rochesters.  





|UPDATED|1/4/2015 11:04:14 PM (AZT)|/UPDATED|




 

1976 Silver/Firethorn.  L48, 4spd.  Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.

Re: 1979 L48 Quadrajet rebuild

Posted: 1/5/15 11:44pm Message 5 of 12
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Vancouver, WA - USA
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Vette(s): 1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.
Sarge81 said: Being a common issue with Rochester carbs, especially 4 spd. cars you might want to also check your primary throttle shaft for slop in it. If you grab the throttle linkage where the throttle cable goes to, try to move it forward, backward, up n down. If there is excessive play you'll want to do or have a bushing kit installed. Otherwise you'll have a vacuum leak there and you'll never get a solid carb adjustment after a rebuild. 
Another thing to do is use a straight edge on all the flat mating surfaces to make sure there is no major warpage. 


Hey, Sarge - what is it about the 4 spd cars that exacerbates this problem?  I've never heard that bit of trivia but I've lived it since my car is a 4 spd and the shaft was pretty sloppy.  






 

1976 Silver/Firethorn.  L48, 4spd.  Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.

Re: 1979 L48 Quadrajet rebuild

Posted: 1/6/15 5:30am Message 6 of 12
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WEST SENECA, NY - USA
Joined: 12/3/2001
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Vette(s): 1981 Blue Ice Met. w/pearl ghost flames TKO500 5speed. LS1 Swap 3.45 Dana 44.
daveo76 said:
Hey, Sarge - what is it about the 4 spd cars that exacerbates this problem?  I've never heard that bit of trivia but I've lived it since my car is a 4 spd and the shaft was pretty sloppy.  



With manual transmission cars your constantly "on and off" the gas when shifting gears. 
Automatics your foot is more steady on the gas since the transmission is doing the shifting for you, hence less wear on the primary throttle shaft. 

On Rochester carbs the throttle shaft is steel and the base plate the shaft sits in is aluminum. That's where these bushing kits come in handy. The shaft will then sit in a brass/bronze bushing instead of the softer aluminum.

Every Rochester 4 barrel I have rebuilt since the mid '80's up until a few years ago, I found the manual trans cars had considerable amount of slop in the primary throttle shaft vs. automatic trans cars. 
Of course the secondary throttle shaft never seem to wear out simply because they never really open and close constantly during "normal" driving. 






GEN III 5.7L "LS6" Engine swap
TKO500 5 spd.
3.54 Dana 44
'69 "N11" Sidepipes
Borgeson Steering Box
Born 8/1981
Sequence #3975




Click here to see more pics of my Vette on CarDomain.


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Re: 1979 L48 Quadrajet rebuild

Posted: 1/6/15 9:40am Message 7 of 12
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Vancouver, WA - USA
Joined: 8/25/2005
Posts: 869
Vette(s): 1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.
Interesting, makes sense. Thanks for the info.



 

1976 Silver/Firethorn.  L48, 4spd.  Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.

Re: 1979 L48 Quadrajet rebuild

Posted: 1/6/15 11:15am Message 8 of 12
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Duncanville, TX - USA
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas
Sarge is right, plus, manual trans cars usually have a little stouter return springs on the carbs, which adds to the accelerated(pun intendedTongue) wear on the shaft bores.
The main thing to remember about shaft bore wear is....Rochester/GM never intended for these carbs to still be running 25-30 years later. Back then, 10 years was a good run, if they lasted that long. So why bother using bushings there to start with? Even now, with throttle bodies on infected cars, there are shafts running in bare, untreated aluminuminum, or even magnesium in some cases. Wacko


Joel Adams
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Re: 1979 L48 Quadrajet rebuild

Posted: 1/6/15 5:19pm Message 9 of 12
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Grapevine, TX - USA
Joined: 8/26/2006
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Vette(s): 1972 LT-1 convertible with factory air. 2017 Black Rose Grand Sport convertible.
Adams' Apple said: Sarge is right, plus, manual trans cars usually have a little stouter return springs on the carbs, which adds to the accelerated(pun intendedTongue) wear on the shaft bores.
The main thing to remember about shaft bore wear is....Rochester/GM never intended for these carbs to still be running 25-30 years later. Back then, 10 years was a good run, if they lasted that long. So why bother using bushings there to start with? Even now, with throttle bodies on infected cars, there are shafts running in bare, untreated aluminuminum, or even magnesium in some cases. Wacko


What's an infected car?   LOL



   

Re: 1979 L48 Quadrajet rebuild

Posted: 1/7/15 10:13am Message 10 of 12
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Duncanville, TX - USA
Joined: 11/8/2003
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas
Uh.....the kind with fuel infectors, of course.....Confused

LOL



Joel Adams
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

in Forum: C3 Fuel, Emission Control, and Exhaust Systems


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