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I removed my carburetor today in preparation for ordering a rebuild kit. Car is a 75 L48. The numbers on the carburetor are 17055038/1406. I've seen several online sites that decode this differently. Some say the first 4 digits make this a 1976 carb and some say that this is a service replacement carb. I've also seen these numbers listed as a truck carburetor so there is lots of confusion. The restoration guide lists 7045222 as the correct carb for this car. I'll probably rebuild what I have if it will work correctly but I want to make sure that I have the correct rebuild kit. Is this an M4MC as the car should have or is it a truck carb that won't be right to use?
From: At my Bar drinking and wrenching in Lafayette Colorado
There is no confusion about that number:
17055038 is a Rochester service replacement carb for a '75 Vette, Nova, and light duty truck. It is a "correct" carb for your Vette, but it is not the "original" carb for your Vette.
From: At my Bar drinking and wrenching in Lafayette Colorado
The photo from CU above is not entirely correct in that it does not show the rear vacuum break, which was on this carb number. Here are some pics of one on my workbench right now:
1975 is unique in that it was the only year that Chevy used a rear vacuum break on the passenger car carbs. 1975 also did not have the Adjustable Part Throttle (APT) feature on the power piston. The rear vacuum break was deleted on the Vette carbs and passenger car carbs after the '75 model year, since it is redundant and not needed.
Lars, I have my 17056211 disassembled. Is there a spec for main well bleed tube and secondary accelerating well tube height in relation to the air horn?
This is what I have:
Main well bleed tubes: 1.168"
Secondary accelerating well tubes: 1.228"
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
Originally Posted by lars
The photo from CU above is not entirely correct in that it does not show the rear vacuum break, which was on this carb number. Here are some pics of one on my workbench right now:
1975 is unique in that it was the only year that Chevy used a rear vacuum break on the passenger car carbs. 1975 also did not have the Adjustable Part Throttle (APT) feature on the power piston. The rear vacuum break was deleted on the Vette carbs and passenger car carbs after the '75 model year, since it is redundant and not needed.
Lars
Pardon the interruption folks
Hi Lars, I tried sending you a PM but your box is full. Im donating a carb to you for anyone who needs it. Its buick or pontiac but Im sure somenone can use it
scott
From: At my Bar drinking and wrenching in Lafayette Colorado
Looks pretty deep, but impossible to say based on that photo. Set the height up as outlined in my paper: .020 - .030" of the power piston above the retainer lip.
From: At my Bar drinking and wrenching in Lafayette Colorado
Originally Posted by Rescue Rogers
Pardon the interruption folks
Hi Lars, I tried sending you a PM but your box is full. Im donating a carb to you for anyone who needs it. Its buick or pontiac but Im sure somenone can use it
scott
Now back to our regular scheduled drinking
Scott -
I don't know what a "PM" is, but I appreciate any donations to "The Cause." My e-mail box is not full. I have a guy with a Pontiac in the workshop right now in dire need of a rebuildable carb, so it may see an immediate donation home - that would be great!! Thanks!!
The choke housing is ruined. The screws were so corroded that they snapped off. I tried to drill out the broken screws and the housing got ruined. I found a few on ebay. Is part # 17051996 correct? I also found another one with part #17055545 if that one is different. They look like they are correct by the pictures but you never can tell.
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
Originally Posted by lars
Scott -
I don't know what a "PM" is, but I appreciate any donations to "The Cause." My e-mail box is not full. I have a guy with a Pontiac in the workshop right now in dire need of a rebuildable carb, so it may see an immediate donation home - that would be great!! Thanks!!
From: At my Bar drinking and wrenching in Lafayette Colorado
Originally Posted by teamo
The choke housing is ruined. The screws were so corroded that they snapped off. I tried to drill out the broken screws and the housing got ruined. I found a few on ebay. Is part # 17051996 correct? I also found another one with part #17055545 if that one is different. They look like they are correct by the pictures but you never can tell.
You cannot simply remove the choke housing screws - they have to be heated up with a propane torch and carefully extracted while hot by rocking them gently back and forth. They will otherwise snap off and destroy the housing, as you have discovered. Once they are extracted, the housing threads have to be chased with a tap to assure correct installation of new hardware. If the screws snap, they have to be very carefully machined out on a mill to avoid destroying the housing.
The part number for the choke housing for your carb is 17051917, but this number is not stamped on the housing, so I don't know how you would ever verify it. As long as the housing looks like this you can use it:
In 1980, Rochester went to the electric choke system, which uses a housing without the hot air bleed provision. You cannot use any housing that looks like this for the electric choke if you plan to use your stock hot air choke system:
I found a nos housing online, it's on the way. Also, the carb has all torx screws which seems odd. All of the pictures of Quadrajet's that I have seen appear to have flat head screws. Is this factory or did someone rebuild it at some point and replace the screws.
Thanks
From: At my Bar drinking and wrenching in Lafayette Colorado
No, Torx are not normal on a pre-80's Q-Jet. If the carb has Torx screws, it is either a commercially rebuilt carb, or a post-'82 carb. Since passenger cars did not use non-computer-controlled carbs after '81, whatever carb you're looking at with Torx screws, if not commercially rebuilt, is either a mid-80s truck carb or a Service Replacement carb built in the 80's. Torx screws are not "correct" or "normal" for a mid-70's carb.
Ok so the numbers show it is a service replacement carb correct for 1975 but the torx tell a different story. Maybe it was rebuilt by a shop at some point as you said. and they replaced the screws. I'll have to dig into this thing and see if I can identify it better.
quadrajet carb numbers
