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The Pitfalls and Dangers of Buying "New" and "Rebuilt" Q-Jets

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Old 11-02-2013, 06:50 PM
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lars
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Default The Pitfalls and Dangers of Buying "New" and "Rebuilt" Q-Jets

Buyer Beware: “Rebuilt” Q-Jet Carbs

For several years, I’ve been warning members on this Forum about the commercially-available “rebuilt” Q-Jet carbs out there. As good Q-Jets are becoming more difficult to find, the “rebuilders” are becoming more devious and deceptive than ever, selling pure junk under the guise of “numbers” and the much-abused “rebuilt” title. And Corvette people are buying these things, thinking they are buying a like-new Q-Jet. Nothing can be farther from the truth.

Here is a carb that is very representative of the crap being sold, and this is why you need to be very wary of buying these “pretty” “new” carbs...

The LS5 454 1971 carb is a rare and sought-after carb. I’ve seen these things sell for $1,200.00, and Big Block owners will cash out for one of these carbs. So here is a smokin’ deal on a completely rebuilt 7041205 carb. It’s all plated, and it looks very pretty:





What could possibly be wrong..? This thing is PERFECT!

Let’s take a look at it…

First, all the plating is wrong. Q-Jets were not built with yellow dichromate choke plates or secondary airvalve plates. The screws were not cad plated. All the cad plated parts on a Q-Jet were simple silver cad, and did not have the yellow dichromate conversion coating. All hardware on a Q-Jet was black phosphate coated. The accel pump lever should be green – not cad plated. This builder went a bit overboard on the plating stuff – it’s a big RED FLAG when the builder doesn’t even know what the correct plating should be.

But that’s not all…

Take a look at the bottom of the carb posted by the seller:


To an inexperienced buyer, this may look just fine. But it’s not… Take a look at a “real” 7041205 carb bottom surface here. My carb isn’t quite as pretty, but it’s a real one:


Notice that the “pretty carb” does not have the power brake vacuum port drilled or tapped at the back of the plate. The “real” BB carb has location for the power brakes – note the fitting installed. Also, note the difference in the configuration of the bottom plate casting up at the forward edge… Here is a photo of a similar bottom plate to the seller’s carb:


Take a look at the carb that it’s attached to:


Yup… that “original” 7041205 BB carb has been pieced together with a 1973 small block carb throttle plate…

But it doesn’t stop there…

Here is the photo of the choke-side of the advertised carb:


Once again, it looks very pretty…. But wait a minute… Let’s take a look at a real ’71 BB Q-Jet carb.

Here’s a real 1971 Choke Pulloff assembly:


Here’s a 1969 pulloff assembly:


Here’s the correct 1971 pulloff assembly installed on a real 1971 carb:


Here’s the 1969 pulloff assembly on a 1969 carb:


…And here’s the “pretty” carb for sale:


The pretty carb has a 1971 choke pulloff bracket and lever system with a 1969 pulloff and 1969 secondary airvalve rod. That means that the pulloff will never operate, and it will never crack the choke open upon startup – it’s completely non-functional…!

So the carb being advertised as being a very pretty, restored, rebuilt 1971 Big Block carb is a mix-n-match carb made up with junk parts from 1969, 1971, and 1973. The carb is complete garbage, and it’s very likely that it cannot be made to run properly, no matter how much tuning work is put into it. But it’s very pretty, and they’ve done a nice job of plating all those junk parts.

This carb will be bought by an enthusiast, and the post on this Forum will be, “Which screw do I adjust to make my Q-Jet run right?” He’ll get 20 responses suggesting fiddling with the idle mixture screws, float level, fuel pressure, fuel filter, secondary airvalve spring windup, and choke adjustment…

The screw you actually adjust with this carb is the release-screw on your trash can lid… Throw this carb in the trash and get a nice, used, non-rebuilt carb that can be set up right.

My advice: Do not buy these “pretty” rebuilt carbs – they are complete junk, and can never be set up to run right.

Lars



Last edited by lars; 11-02-2013 at 06:56 PM.
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Old 11-02-2013, 07:36 PM
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63vette427
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That's a great write up Lars.. You were a great help to me as i was working through finding the right carb for my car.. Sadly i would have bought one just like this if it wasn't for your advice..
Old 11-02-2013, 07:46 PM
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Default Happy Holidays!

Hi Lars,
What are we to do? The first carb I sent to you was just like the basket case you describe.
Seems like many of the parts fit together but did not work correctly.
Just by looking at a part I could never tell what year carb it originally was made for, and i'd bet few others could either. So I for one am glad you are here to help us out.

Corvette owners love clean, pretty and shiny! My rebuilt carb is not any of the above but it works great and it's under a big black air cleaner so no one see's it anyway.
Enjoy your weekend, Peter G.
Old 11-02-2013, 07:49 PM
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Hmmm, interesting! I had been considering a Q-jet to replace my Holley, maybe I'll stick to the Holley simply because it's new instead of rebuilt and I know everything that should be there is there. Don't have the experience to spot these sorts of flaws with a Q-jet.
Old 11-02-2013, 08:03 PM
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Lars,

Nice write-up as usual! I don't mind playing the fool on this subject. About four years ago I had some carb problems with my 1974 L-48 with TH400. So I found what seemed to be a reputable rebuilder on-line. I purchased this #7044206 Q-Jet (Carter version) and as you say it sure looked pretty when it arrived! I installed it and no way short of every which way but loose would it perform properly. Timing, dwell, etc. fine. And even then....Mind you I am just a backyard putter-around Vette owner so I laid the blame on myself.

I had the old dirty original carb cleaned and rebuilt locally by someone who still knows these devices. It has performed very well ever since, up to last week and over many miles.

The pretty unit sits in the basement. And it still looks very nice. But I don't have the heart to put it in the trash bin!!

So here you go: the glamour side of Q-Jets.








Last edited by Paul L; 11-02-2013 at 08:12 PM.
Old 11-02-2013, 09:16 PM
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Then there is me, olde phart here, who had a Qj hanging off the garage walls for some 25? years, and so it was not a Rochester build....

but it hung around with it's great throttle blade lack of wear....

and so I pulled it apart for use on a motor home maybe 4 years ago...

still on there, starts/runs just fine....

can't complain at 8-9 mpg....8000 lbs motor home chassis....

Old 11-02-2013, 10:30 PM
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lars
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Originally Posted by petes74ttop
Hi Lars,
What are we to do?
That's a question I get a lot, and the answer is quite simple, even if nobody wants to hear it.

"Lars, I can't find a good carb, so I have to buy this junk!"
"They don't make new carbs any more, so I have to buy whatever is offered by the rebuilders!"
"I can't build my own carb, so I have to buy whatever eBay is selling!"

Here is the deal and the facts:

First, don't buy crap from scammers. If you chose to buy cheap junk, as shown above, from people who are ripping off enthusiasts, you're setting yourself up for failure.

Next, you need to get this into perspective. The C3 Vette is now 46 years old, and so are all the parts. That's half a century. In 1979, when many of these Vettes were new, the guys working on 46-year-old cars were working on 1930 Duesenbergs and Auburns. Do you think there were new Stromberg EE-3 carbs available in 1979..? Do you think you could buy a nice, perfect, unmolested Schebler Model S 1-1/2 or a Carter BB-1 in 1979? You couldn't then, and you can't now.

Likewise, you cannot buy a nice, new 46-year-old Q-Jet for an antique Vette now - you're no different from the guy trying to restore a 1930 Stutz in 1979.

What we're going to see are 2 categories of Corvettes: There are guys who are unwilling to pay the price in terms of money and effort required to put together a good, undamaged Q-Jet carb that is "correct" for the car. These guys, and their cars, will end up with Holley Street Avengers and Edelbrock "Performer" (a re-pop of the old Carter AFB) carbs, and the cars will suffer a depreciation due to the incorrect configuration. There will always be a market for these altered and incorrect cars, and they'll always be fun to play with. Lots of power and performance is available, and there will always be a market segment for these cars. I'm not knocking it.

The guys who want to keep the cars correct and original are going to have a continuing challenging time. Correct, unmolested and undamaged Q-Jets are going to be much more scarce - there is a finite supply. We are going to see prices for good rebuildable cores rise sharply, and I predict it will not be uncommon to see good, undamaged Q-Jets selling in the $1000-range - even for small-block carbs. People wanting a "correct" carb will have to start scrounging junk cars, garage sales, barns, and junk barrels. It is going to be just like finding and piecing together a Stromberg EE-3. Further, there are only a handful of people left in this country who can correctly build a Q-Jet, and as these people die and leave the industry, it will be increasingly difficult to piece one together.

There is no easy, pat solution. If you find an original, un-rebuilt, unmolested Q-Jet off of a Chevy passenger car for your year Corvette, I suggest you buy it and keep it. If you have a Q-Jet on your Vette, I suggest you take very good care of it and don't over-torque the bolts and screws (the most common way to destroy a Q-Jet). Don't have your carb rebuilt by someone who doesn't know what they're doing for the sake of saving a hundred bucks. And don't ever "exchange" your original carb for a "rebuilt" carb from any parts store or Internet firm. If you find a carb for sale, have someone who knows what they're looking at evaluate it before you buy it - I run an evaluation service and will be glad to give you my slanted opinion on any Q-Jet.

Good luck with your searches and scrounging for good parts and carbs... Don't let the rip-off guys get the best of you!!

Lars

Last edited by lars; 11-02-2013 at 10:39 PM.
Old 11-02-2013, 10:39 PM
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An amazing analysis and service to the community - thanks, Lars.
Old 11-02-2013, 11:25 PM
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Originally Posted by Tudz
Hmmm, interesting! I had been considering a Q-jet to replace my Holley, maybe I'll stick to the Holley simply because it's new instead of rebuilt and I know everything that should be there is there. Don't have the experience to spot these sorts of flaws with a Q-jet.
I agree. I remember the days when you could literally get Q-jets at the junkyard for 5 bucks. Those days are long gone, so if you have your original Q-jet, or even a non-original that runs well, treat it like gold! If not, run a Holley or Edelbrock, and just don't worry about it. Summit makes a good street carb, and the Street Demon looks like it might turn out to be a good street carb, too. (kinda reminds me of an old Thermo-Quad.) There are scrillions of rebuildable Holley 1850 and 3310 carbs out there. 50 bucks and a rebuild kit, and you're in business, because you could teach a chimp how to rebuild a Holley carb. Might take awhile, but you could do it, if you had the patience.

Also, I have to find fault with Lars's "40 year" comparison. In the last 40 years, technology has changed a lot more than it did in the 40 years prior to that, so it's even worse than he claims! Sorry, Lars, but I gotta call 'em like I see 'em!

Scott
Old 11-03-2013, 12:25 AM
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Nice write up Lars! Your are spot on. When I look for a vette I look for the most original untouched/modified car that I can find. It's a lot easier to fix or restore something that bubba has not had his hands on.

With that said I have a very original 72 4spd with the original carb (7042203}
The fuel line inlet has been stripped on it and I was wondering what the best option is to repair it. Should I install the oversize inlet such as the ones offered by parts stores or hunt for the correct numbered carb body? I have a 73 carb on it now and it runs flawless, but not having the original carb on it bugs me.
Old 11-03-2013, 12:45 AM
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Years ago I hit a boneyard that was going out of business. All you could carry for $20. I managed to find a old 4dr Cutlass with a 350.
I didnt think twice about the carb on it when I pulled it off.
Took it home and cleaned it up. Found out it was a # 7040256 .70 Olds W30 4speed Rochester, A super rare carb.
Years later sent it off to a Carb Shop in Cali to have it overhauled. What a mistake. One of the biggest gaffes they did was put needles and Needle hanger/piston & spring in it for the primary jets.
70 W30's with a 4spd had such a big cam in them from the factory they wouldnt develop enough vacuum at idle to operate a typical primary metering system with needles and jets. So no primary metering needles were ever installed in these.
After finally rebuilding it myself and learning how carbs are supposed to function I was able to tune it and get it running properly(sans the primary needles)

I still would like to take a lesson or 3 from you Lars
Old 11-03-2013, 01:17 AM
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Originally Posted by AzMotorhead
Years later sent it off to a Carb Shop in Cali to have it overhauled. What a mistake.
20 years ago I needed a QJet for my 68 L36, when the engine was overhauled. I bought from the Carb Shop, because I wanted the best... $400 later, they sent me the carb built specifically for my car. Well, what a piece of mierda. Here's a review; I cannot bear to list all the mistakes. Today this carb is one of Lars' show pieces and is right at home on my old Chevy.

http://forums.corvetteforum.com/c3-t...et-photos.html
Old 11-03-2013, 07:43 AM
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Good thread Lars.

Several year back , I sent my Z28 Camaro Qjet off , not knowing "who" to have restore it. it's a fairly htf 4sp carb. ...it turned out decent and car runs nice. They plated the little green pump arm thingy gold . Turned out that I was lucky , as other people I know got back junk from this expert . So I counted myself very fortunate , maybe my restore was an easier one . I would not recommend them again.

You are so right about over tightening the carb screws and bolts.

The list of people who I trust or now know to be true experts on Qjets is indeed a very short list.

good news is ......once it restored right , it will last a very long time.
Old 11-03-2013, 10:01 AM
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Originally Posted by tx75vette
I have a very original 72 4spd with the original carb (7042203). The fuel line inlet has been stripped on it and I was wondering what the best option is to repair it. Should I install the oversize inlet such as the ones offered by parts stores or hunt for the correct numbered carb body? I have a 73 carb on it now and it runs flawless, but not having the original carb on it bugs me.
Don't put the oversized inlet in it - it is only a temporary fix, and it can destroy the inlet to the point that it can't be correctly repaired. You can send the carb out to me for a correct fix with a stainless thread insert. This will permanently repair the inlet so that you can still use the in-carb filter and the original inlet fitting. Drop me an e-mail for my Services Info Sheet for a complete run-down on the thread repair service.

Lars
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Old 02-05-2019, 08:31 AM
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Guys,
I sent my 7042203 carburetor to Lars, he keeps you informed about what was or wasn’t bubbaed up. Tests the carburetor on one of his engines & tuned to corvette specs. This man is a legend for carburetors & distributors. Well worth the price. You will never have a problem again.
Thanks
Mark
Old 02-05-2019, 09:28 AM
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Originally Posted by lars
Next, you need to get this into perspective. The C3 Vette is now 46 years old, and so are all the parts. That's half a century. In 1979, when many of these Vettes were new, the guys working on 46-year-old cars were working on 1930 Duesenbergs and Auburns. Do you think there were new Stromberg EE-3 carbs available in 1979..? Do you think you could buy a nice, perfect, unmolested Schebler Model S 1-1/2 or a Carter BB-1 in 1979? You couldn't then, and you can't now.

Likewise, you cannot buy a nice, new 46-year-old Q-Jet for an antique Vette now - you're no different from the guy trying to restore a 1930 Stutz in 1979.

What we're going to see are 2 categories of Corvettes: There are guys who are unwilling to pay the price in terms of money and effort required to put together a good, undamaged Q-Jet carb that is "correct" for the car. These guys, and their cars, will end up with Holley Street Avengers and Edelbrock "Performer" (a re-pop of the old Carter AFB) carbs, and the cars will suffer a depreciation due to the incorrect configuration. There will always be a market for these altered and incorrect cars, and they'll always be fun to play with. Lots of power and performance is available, and there will always be a market segment for these cars. I'm not knocking it.

The guys who want to keep the cars correct and original are going to have a continuing challenging time. Correct, unmolested and undamaged Q-Jets are going to be much more scarce - there is a finite supply. We are going to see prices for good rebuildable cores rise sharply, and I predict it will not be uncommon to see good, undamaged Q-Jets selling in the $1000-range - even for small-block carbs. People wanting a "correct" carb will have to start scrounging junk cars, garage sales, barns, and junk barrels. It is going to be just like finding and piecing together a Stromberg EE-3. Further, there are only a handful of people left in this country who can correctly build a Q-Jet, and as these people die and leave the industry, it will be increasingly difficult to piece one together.
Wow.....you do not know how many times I tell this to people and about half dismiss me as being a kook........."you can find anything on the internet!....you're just not trying hard enough!........I know a guy I can take it to, that's ok......."
Problem is that they do know a guy we can take it to.......we all know a guy we can take our stuff to......but does he know s&%t from shinola? He will tell you he does......
Between a wannabees pride and the scammers lies a land of a handful of people who know how to do things the correct way because they studied it and truly understand how something works.......
I almost gave up a few years back and shut my modest little hobby garage down here because dealing with Know-it-Alls had run its course with me. I would not do exactly what they asked because it is incorrect and I was not sticking my name on something that stunk........
I do not know everything, but I also don't do Q-jets anymore because the support and cores are just gone........but I DO service Holley's, Demon's, Carters, even 2 Jets......along with any Vintage japanese motorcycle carb out there........amongst others......but you have to understand the amount of time and research that goes into what I do is greater than performing the job itself.......that is because the 80's were 35 years ago and the 70's 45 years ago...........if you like to bitch that O'Reilleys cant just pull a valve cover gasket for your small block off the shelf by description, then you do not need to speak to me.........in fact do not speak to me as you just dont get it......and it is not my job to explain.

Anyhoo.........thanks Lars for the awesome perspective........sorry for the rant

Jebby

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