C3 Tech/Performance V8 Technical Info, Internal Engine, External Engine, Basic Tech and Maintenance for the C3 Corvette

Fake, Re-Stamped Commercially Rebuilt Q-Jet Carbs

 
Old 03-02-2019, 10:36 PM
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lars
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Default Fake, Re-Stamped Commercially Rebuilt Q-Jet Carbs

Many of you have followed my posts and threads over the past 20 years, warning of the perils of the dreaded “commercially rebuilt Q-Jet carbs.” As these carbs are getting older and harder to come by, more and more people are getting conned into buying one of these terrible, commercially built carbs. But the other phenomenon we’re now also seeing is the emergence of a lot of “fake” re-stamped carbs. The 1968 and 1969 Corvette 427 carbs are very rare, so commercial builders have no problems “creating” these rare carbs and selling them for a substantial amount of money – often exceeding $1000.

One of our Forum members has been trying to come up with a good, correct carb for his 4-speed ’69 427. He has managed to collect 3 carbs, and he sent them to me for evaluation. Let’s take a look at these 3 carbs. Of the 3 carbs, which carb do you believe is the best carb to use?




All 3 carbs are carb number 7029215, which means they are 1969 427 4-speed carbs. As you can see, the two carbs to the left are very pretty... they are commercially rebuilt carbs, sold as "real" '69 427 carbs. The carb to the right is a carb sold as a "good, rebuildable core."

Let's look at the carb to the far left first....

Here is the ID number on the carb:


The photo below shows what the ID stamping looks like on a real 7029215 carb. You can really spot the difference in the stamps if you look at the "EH" stamps. Most fake numbers also have the "O" almost round, whereas the real numbers have a vertically drawn-out "0":


The commercially rebuilt carb is a fake re-stamp.

One look at the throttle lever provides another give-away. Here is a real '69 427 throttle lever. Note the rounded top edge, the way it is swaged onto the shaft, and the clean-cut lower edge to clear the BB manifold exhaust crossover:


The commercial carb actually has a Pontiac throttle plate. To use the Pontiac plate, the builder has modified a small block Chevy lever by hacking off the bottom, drilling some holes, and screwing it onto the Pontiac throttle shaft lever:


On the passenger side, the commercial carb is missing the secondary lockout lever, and the choke pulloff mounting plate is some odd, home-fabricated plate that was never used by Rochester:


This is what it should look like:


The choke lever is also a Pontiac item which normally interfaces with the Pontiac secondary airvalve lockout tang, which is not used on Chevy carbs:


The '69 427 Chevy choke lever can be seen here. It's a lower profile, and uses a much shorter choke intermediate rod:


The commercial builder went to trouble to form a poorly-made idle vent cover and to plate it with the incorrect plating color. The wire lever connecting the accelerator pump lever arm to the idle vent was deleted, making the idle vent system inoperable:


The correct, complete system looks like this when installed:


Notice how nicely the real "doghouse" fits on the carb:


On the inside, the commercial carb is really messed up on the jetting. The secondary rods installed are "CZ" rods, which are so fat and lean that the secondary operation of the carb would be dangerously lean. The fat "CZ" rods compared to the correct "AX" 427 rod on the right:


The commercial builder set the float level extremely low, further leaning out the carb. Non-original aftermarket IFR tubes can be seen installed - these are undersized, and will not flow adequate idle fuel:


To help offset the lean condition, they installed lead plugs in the idle air bypass hole passages:


Incorrect primary metering rods are installed, and the rod retaining spring has been deleted:


To further lean it out, the APT (aka, power piston height) has been set extremely low, which will cause a bad lean condition at cruise:



The second commercial carb is not much better....

It has been stamped with a Carter carb number. The "70" prefix on most Q-Jet carb numbers is the Rochester designator. Most Carter-built carbs deleted the "70" prefix. But notice how the "29" numbers are a different size than the rest of the numbers. Also, most Carter-built Q-Jets in '69 were identified with an embossed foil tag on the driver's side of the float bowl:


You can see where the original round Carter ID emblem has been removed from the float bowl:


The float bowl, in fact, is not even a 1969 bowl - this casting feature on the forward driver's side, along with the vacuum nipple configurations in the bowl, identify it as a 1972 float bowl:


Continuing with the "mix-n-match" creation of this carb, flipping the carb upside-down shows that the throttle plate is not a 1969 throttle plate: The '69 throttle plates had 3 screw attach holes. They also do not look like this:


1969 throttle plates look like this:


...and 1969 throttle plates do not have power brake booster vacuum fitting holes in the back. The throttle plate on this carb is a 1973 small block Chevy throttle plate:


They plugged the EGR vacuum nipple passage in the 1973 throttle plate with a ball bearing:


The builder must have had an abundance of Pontiac choke levers, because this carb, too, has a Pontiac lever intended for use with the Pontiac style airvalve lockout system:


But on this carb, the choke has been poorly pieced together from a few different carbs, and the workmanship leaves a little to be desired:


The hacked system was modified in such a way that the choke fast idle cam lever arm did not extend under the fast idle cam, making the fast idle cam completely inoperative. Photo shows the fast idle cam in the low position, with the cam support lever arm raised and disengaged from the cam. The support lever arm is actually cut short, and is too short to reach and support the fast idle cam:


Once again, the wire actuation lever is missing off the idle vent system, making the idle vent inoperative:


Wrong secondary rods installed. Not quite as bad as the rods in the first carb, but still far too lean for the 427 application:


Really nice screws in the choke plate....


Primary rods in the carb should be 45's. The commercial hacker installed size 36 rods. This carb would have run grossly rich at cruise. At least they installed the rod retaining spring in this carb...


For the price the guy paid for this carb, you would have thought they would have installed a new float... No such luck. The float level is extremely low, and removal of the float shows the entire bottom surface of the float eroded and decaying from years of use. They actually installed a used float:


No lead plugs in the idle air bypass hole passages on this carb. Hooray..!

And now the "rebuildable core" carb...

This carb is rough. Really rough. And it's a little odd: The carb numbers are not the same font size as all other carbs of the same year and type. The numbers are different from the "real" 7029215 carbs I have in my collection, making the carb a suspect re-stamp. However, the carb is so rough that the motivation to re-stamp it makes no sense. And since the carb has not been re-plated, a re-stamp would be tough to cover up. But these numbers do not look like the "real" numbers that should be on the carb - they're too small:


A quick check of the IFR tube lower orifice size indicates that the float bowl is a small block-calibrated bowl. The IFR does not have the larger-diameter metering hole used on the 427 carbs, further giving suspicion to some odd alteration of the ID number. But it doesn't make sense, and there is no obvious or clear indication of the alteration.

But this carb does have the correct 427 throttle plate and linkages. This is all correct and original big block stuff:


The airhorn is a correct 1969 airhorn, and the choke plate is the correct plate with the single horizontal rib running from side-to-side (notice the photos of carb #1 above - the choke plate does not have the horizontal rib, so the choke plate is not a 1969 choke). The carb is missing the "doghouse" and the wire actuation lever for the idle vent:


On the choke side, the choke pulloff mounting plate is a correct '69 plate, but a 1970 pulloff (broken) has been installed. It is missing the correct '69 plastic fast idle cam, and the secondary airvalve rod is bent, altered and damaged. The choke intermediate lever is missing, as is the choke intermediate rod. Lots of corrosion and rust:


The throttle plate is the correct 3-screw throttle plate, but it's missing one of the correct idle mixture screws:


The fuel inlet threads are completely eroded and stripped out, and the inlet fitting and spring are both missing:


On the inside, the power piston is missing its hanger arms, the primary rods are gone, the secondary rods are missing, and the secondary rod hanger is missing. The jets are the wrong size, and are not usable. Most of the hardware in the carb is damaged or missing:


Where does this leave us..? If I give benefit of the doubt to the ID stamping, which could be legitimate, carb #3 is the hands-down winner to build a well-running, "correct" carb for the '69 427 project. The 2 "pretty" carbs are complete junk, and don't even have enough usable parts to get carb #3 into serviceable condition. So it's off on a scavenger hunt in my carb storage shed to find the parts needed to bring this sorry-*** carb back to life...



Lars

Last edited by lars; 03-03-2019 at 12:30 AM.
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Old 03-02-2019, 10:55 PM
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427Hotrod
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Really amazing info Lars. Your knowledge of these never ceases to amaze! Thanks for the lessons!


JIM
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Old 03-03-2019, 07:20 AM
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Thanks for all the great details Lars. Damn shame how shoddy some of these "rebuilt" carbs are.
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Old 03-03-2019, 07:29 AM
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Never get tired of saying excellent post Lars. Your continued efforts to save us from ourselves are admirable to say the least. Very interesting stuff!
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Old 03-03-2019, 07:54 AM
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For some reason these carb post just fascinate me....Thank you Lars for all the info you provide and the education I get from reading them.

Brian
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Old 03-03-2019, 08:13 AM
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Lars, Thanks for the education. I'm feeling bad for the fellow that sent you those carbs.
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Old 03-03-2019, 09:33 AM
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In 2016/17 I discovered the fuel inlet on my "215" was JB Weld and aftermarket repair kit so it took quite a while to find a replacement. ($1,300). After the fact learned there are folks out there that can repair the threads on the inlet. As it is 23 degrees and snowing in SW Missouri may go to the attic and compare the takeoff to the great pictures Lars provided. Many thanks to his generous sharing of knowledge.
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Old 03-03-2019, 10:24 AM
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Good stuff.
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Old 03-03-2019, 10:39 AM
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Originally Posted by sshort67 View Post
After the fact learned there are folks out there that can repair the threads on the inlet.
Yes, the inlets can be repaired - I have the tooling and equipment to do the correct repair.

Lars
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Old 03-03-2019, 11:19 AM
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Thanks Lars for that amazing post.
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Old 03-03-2019, 12:37 PM
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Always interesting! Thanks for taking the time and effort to put these posts together.

I’ve noticed that you often post that the floats are set up too low. Is this by design to put a little more pressure on the float valve or just laziness?
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Old 03-03-2019, 01:23 PM
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I imagine that people set the float to the wrong spec for the same reason that they set their timing to the wrong spec, set tire pressure to the wrong pressure, and set their clocks to the wrong time...

Lars
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Old 03-03-2019, 02:37 PM
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Hey Lars, Quick question - a source for metering rods for the Q-jet? Other than swap meets, trying to find a good source is getting tough!

Thanks,
walt z.

- Other than the 300 rods in your parts box, of course!! :-)

Last edited by wzschirnt; 03-03-2019 at 02:38 PM. Reason: new info
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Old 03-03-2019, 02:50 PM
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My papers outline all the sources for the various rods. Only a few select rods are available, and almost none of the 1975+ M4M passenger car primary rods are available. I try to update the sources and availability in my papers as time permits, so the listing is fairly current and accurate. The rods that are not available can only be obtained by stripping down used parts carbs.

As a reminder, don't use any of my papers you find posted around on the Internet - I don't post my papers, and those posted by others are always obsolete and often altered. E-mail me a request for current copies.

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Old 03-03-2019, 03:09 PM
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Amazing as always...Thanks
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Old 03-03-2019, 03:10 PM
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I would call restamping the incorrect parts fraud.
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Old 03-03-2019, 03:20 PM
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Very interesting post.

Over in the audio/electronics world we have to be careful about fake electronic components being restamped with numbers of obsolete/nla parts, is any hobby safe from these cheating scumbags?
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Old 03-03-2019, 03:27 PM
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Hello Lars,
Thank you for sharing your knowledge.
I have been studying the 69 carb stamps for a fairly long time. I am not a rebuilding expert such as yourself, but I do know stamps and the many variations on the 69 Rochester carbs. They did make some changes during different times regarding stamping. I have a very large photo library of original carbs I have taken over the years. I am a fan of the 390hp cars.

The car dated 0919 is definitely a fake. No doubt.

The carb with no date (second picture I believe) looks very good. I would say real

The carb dated 0389 is almost certainly a fake. Also, Carter stamped carbs that I have seen used a different date system. They did not use the Julian system but instead a letter for the month and then a number.

I believe the carb dated 0379 is real. For some reason the 215 carbs dated in that range have that different font but they all look exactly the same. I also have pics of legit carbs dated 0389 that look exactly the same as that. Its smaller numbers and very specific. Also I have some for different applications (different part numbers) with the same fonts stamped in. I am almost sure that one is real.

I will post pics later if anyone wants to see other original carbs with these different fonts all with the same date.

It should be noted that the date stamp started to show up on the body sometime in late Nov-Dec 68. These carbs (215's and probably others) also must have been made in batches as many specific dates are common. A common date for production was 3548 for example. Prior to Dec 68 the dates were on the base from what I have observed.
Other common dates are Jan 20 and 21st, Feb 6 and 7th, etc.

Sincerely,
Ed

Last edited by ed427vette; 03-03-2019 at 03:31 PM.
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Old 03-03-2019, 03:41 PM
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Excellent info, Ed - much appreciated. I have relayed my suspicion to the carb owner that the 0379 carb is likely real, even though the IFR tubes do not have the normal big block orifice spec and the stamp size/font is different from the verified real carb in my collection (and other carbs I have of the same vintage). Knowing all the variations on this is key to sorting out the gold from the horseshit...

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Old 03-03-2019, 03:49 PM
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Originally Posted by Big2Bird View Post
I would call restamping the incorrect parts fraud.
In my opinion, selling these completely junk carbs as "rebuilt" carbs is fraudulent all by itself, regardless of the fake numbers..! Unfortunately, "fake" and junk parts are a common problem in the auto parts business, and it's only going to get worse as the value of the real parts continues to rise. Your best defense is to be aware of the problem and to educate yourself before buying junk. Thus the reason for my posts...

Lars

Last edited by lars; 03-03-2019 at 04:04 PM.
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