[Jimbobeast]

Photo:

[unruhjonny]

/\ that is a service replacement tat was manufactured on the 301st day of 1976.

Originally Posted by Jimbobeast

OK, thanks to all for the replies. The "not in plastic" 7040263 NOS carb that has sat on a shelf since 1970. Should I rebuild it purely due to age, or try it on the car first?

If that last image is the same carb you mentioned in your prior post, then that most certainly has not been sitting that long.
Frankly, I'd leave it as-is if you intend on selling it.

[Jimbobeast]

I'm leaving the NOS in plastic carb in the plastic.
The other carb 07040263 was in a box for 51 years but not in plastic. This is the one I am using.

[unruhjonny]

gotcha;
Generally, I am sure you know this, but it is worth mentioning that like with the RA application number carbs, if it's an original (as in time of manufacture) carb, the date code will have a bearing on the value.

I looked for a LOOOONG time for a later date code 7040263 carb for my car - it seems most were made well in advance to the start up of the 1970"+" Firebird production.

[Jimbobeast]

The suspense was killing me, so I made a slit in the plastic and checked out the number on the carb. It WAS different from the box.

As you can see, it has the identical number to the other NOS carb (the one in the box but not plastic), but with a different build date (both 1976)

07040263
2756

So, if I understand things correctly, this is a 1970 service replacement Federal Quadrajet for a manual transmission car, manufactured on the 275th day (November 2) of 1976

This is a non-Ram Air carb, but would it be correct for either a 1970 400 or a 455?

[Jimbobeast]

Wow, my head is spinning. Maybe I'll just get a Holley and be done with it...

[Baron Von Zeppelin]

Originally Posted by Jimbobeast

This is a non-Ram Air carb, but would it be correct for either a 1970 400 or a 455?

It would only be correct for a 1970 400 cid with Manual Transmission.
GTO or Formula or GrandPrix
(non-RA as you mentioned)

It will run and drive fine on any V8 Pontiac with a corresponding Intake Manifold.
An automatic would need a modulator valve vacuum port below the choke pull-off vacuum port on the front of carb - or just be shifted manually all the time.

[padgett]

Yes, the leading "0" was added in 1975, an original would just have 7040263.
AFAIR the only difference between a 263 and a 273 was the 273 had slightly richer jets. Gonna have to dig out my Rochester manual. Know it is here "somewhere".

ps never saw a Holley I could not make leak.

[Kenth]

I have found there is a long list of differences between a 0263 and a 0273.
These differences are not to be found in any "Rochester" book.
Anyone ever took apart and measured the calibration in both carburetors, would have known that the difference is more than the size of the jets.

FWIW

[Old Goat 67]

Originally Posted by padgett

ps never saw a Holley I could not make leak.

PS, Never saw a Holley that ran as well as a Quadrajet either.

[unruhjonny]

Originally Posted by padgett

AFAIR the only difference between a 263 and a 273 was the 273 had slightly richer jets. Gonna have to dig out my Rochester manual. Know it is here "somewhere".

the fuel metering (jets/rods) is different between the two, in large part (as I have understood it) because of the POE;
I also understood when I started looking for a carb for my own car that a great deal of the fake 70 RA carbs were based off of a core 7040263 carb.

[padgett]

Not surprising, just have to fill/restamp one digit.

Does this help ? Now I just need to find the binder with the parts list. Would not believe how much I've collected over the years...

[Jimbobeast]

Oh my, so much information. Thanks to all. I thought there would be one simple reply. Who knew...?

Now, not to hijack my own thread (more of a detour, really), but I have another question. Did the Ram Air carbs (the 67 numbers) have one, two or three vacuum outlets on the front of the carb? I'm referring to manual tranny units.

The carb now on my 1970 Judge convertible has the correct identification number (7040273) for a Federal, Ram Air, 4-speed, but methinks it be a forgery. It's a RA IV, 4-speed car with all other numbers matching. Also, where do all the vacuum ports go? The rear port goes to the brake booster, the right front port goes to the choke vacuum. Where does the vacuum for the ram air flappers, the distributor vacuum advance and the TCS unit come from? Also should there be another vacuum port coming off the choke vacuum canister?

The following photos show the carb stamping (What is WC?) and the front of the carb with 3 vacuum ports. Was this originally an automatic carb?

Inquiring minds want to know...

[padgett]

Few months ago I removed the QJ that was on my Judge to rebuid and replaced with a 263 but cannot make out the last digit. a "7" is hidden under the bar and date code is 2069 which sounds about right. It has two small vacuum hoses on the front one to the choke pull off that only has one connection. Suspect the higher one is for a ported vacuum (70's thing) to the distributer.

Any suggestion on how to make the numbers more distinct ?

[Joe's Garage]

This is a general response to both of the above posts.

Manual transmission 1970 carbs only had one port on the front - the one going to the choke pulloff.

The 'WC' code is a ‘pick code’ and would show on your build sheet. It was used at the factory to designate which carb to install on which vehicle.

The 2nd port on a quadrajet carb (the one that is above the choke pulloff port) is larger in diameter because the metal line from the modulator actually fits into it, with the rubber hose acting as a seal between the carb and the line. That makes carbs with THAT fitting automatic transmission carbs originally.

The 3rd vacuum port on the front, on the driver's side, stopped after the 1969 model year. It was replaced due to the stricter emissions requirements.

1970 carbs did NOT have a ported vacuum port for the vacuum advance - that was handled by a combination of the TCS solenoid and the vacuum switch that measured coolant temps. The vacuum source on the carb was the tree on the back of the quadrajet, which also fed vacuum to the power brake booster and to the controls for the air conditioning on A/C vehicles.

Vacuum for the hood flappers comes from the fitting in the top of the #1 cylinder runner on the intake. It runs to a thermostatic switch in the base of the lower air cleaner shroud and then runs to the upper ram air plate, where is splits and goes to the two vacuum pods. The thermo switch opens or closes the vacuum flappers depending on the temp of the air going through the air cleaner assembly.

The 2nd fitting on the choke pulloff would have had a hose that went to the vapor canister/vacuum tank located on the front of the passenger-side inner fender. It delayed the secondary flap opening and also was designed to control the fumes from the fuel remaining in the intake manifold when you shut the engine off.

I’m pretty sure that the fitting on the driver’s side front of the 7040273-stamped, 0070-dated carb should not be there – at least I’ve never seen one on a legit 7040270 or 7040273 carb - although it could have been added by someone in the past fifty years….

The surface of the vertical rib on the 0070-dated carb looks to be smoother than the rest of the main body casting to me. That would make me suspect that it is a restamp.

The numbers on the carb with the 2069 date-code are a little harder to read – to me at least.

Is the final digit a ‘0’ or a ‘3’ ? If it is a ‘3’, I’d feel like it is also a restamp, since it has the vacuum modulator port, which should only be on a 7040270 carb.

In addition to that, the font on the 2069 carb differs slightly from the date-code to the part number. And the part number digits are crisper – they reflect the light from your camera differently and look sort of shiny. They also appear to be more 'uniformly' stamped, which is another sign of a restamp.

My 02 cents.....

[Kenth]

Originally Posted by Joe's Garage

The 2nd fitting on the choke pulloff would have had a hose that went to the vapor canister/vacuum tank located on the front of the passenger-side inner fender. It delayed the secondary flap opening and also was designed to control the fumes from the fuel remaining in the intake manifold when you shut the engine off.

FYI, the choke pull-off with two fittings is a non-RamAir unit used only for 1970 Pontiac and Cadillac carbs.
It´s part of the 1970 choke delay system and the second fitting is connected to a vacuum tank at passenger side inner fender.
This system delayed chokeblade action so the engine would not stall at cold starts due to the leaner mixtures used.
Also, 1970 non-RamAIr carbs, like the 1969 non RamAIr carbs, uses the primary POE system to compensate, at heavy loads, the lean main cicuit used for these units , and since the POE ports are located below the chokeblade edge it also helps at cold starts.
RamAir cars did not use this choke delay system and used a plastic choke pull-off with one port.

The 1970 choke pull-off has nothing to do with any vapor canister or to control any fuel fumes at shut off. Only California units used the E.E.S. system 1970 and the port for the coal canister is on the throttle plate located between the mixture screws.

BTW, the choke pull-off on OP pics is mounted 180° wrong, making airvalve action less than optimal.

FWIW

[Kenth]

Originally Posted by Jimbobeast

Oh my, so much information. Thanks to all. I thought there would be one simple reply. Who knew...?

Now, not to hijack my own thread (more of a detour, really), but I have another question. Did the Ram Air carbs (the 67 numbers) have one, two or three vacuum outlets on the front of the carb? I'm referring to manual tranny units.

The carb now on my 1970 Judge convertible has the correct identification number (7040273) for a Federal, Ram Air, 4-speed, but methinks it be a forgery. It's a RA IV, 4-speed car with all other numbers matching. Also, where do all the vacuum ports go? The rear port goes to the brake booster, the right front port goes to the choke vacuum. Where does the vacuum for the ram air flappers, the distributor vacuum advance and the TCS unit come from? Also should there be another vacuum port coming off the choke vacuum canister?

The following photos show the carb stamping (What is WC?) and the front of the carb with 3 vacuum ports. Was this originally an automatic carb?

Inquiring minds want to know...

A 7040273 do not have a port for A/T or a timed port for distributor advance.
And the choke pull-off is for a 1970 non-RamAir carb. Yours sits 180° wrong.
Also the throttle plate has a plugged PCV port.
Sincs your carb is composed with parts from at least 3 different units it qualifies as a "Frankencarb".
Need pictures from all sides to see were the parts came from.

[Jimbobeast]

BTW, the choke pull-off on OP pics is mounted 180° wrong, making airvalve action less than optimal.

Please explain above

[Jimbobeast]

Hey, this thread made the "What's New on the PY Online Forums" page today. I feel so honored...

[70TA-RAIII]

That's where I saw it. Good info!

John