Original vs. Service Replacement Quadrajet

[Patrick H.]

Re: Original vs. Service Replacement Quadrajet

FYI, the triangular pad shown became standard on all Quadrajets for 1971 and later. It's used to hold a bracket. So, it's just not present on original 1969s and 70s, but should be expected on all Quadrajets thereafter.

[Edward J.]

Re: Original vs. Service Replacement Quadrajet

Hi Ed, just wondering what the number on your service replacement carb is. I have a '72 LS5 and the carb is a 7042220 dated spring of '72. Runs great and looks like an original except for the last two digits, silly numbers : )

Tom, I took a look at my 72 and the service number is 7042207, the original number is a 7042202 if I remember correctly.

[Joe L.]

Re: Original vs. Service Replacement Quadrajet

FYI, the triangular pad shown became standard on all Quadrajets for 1971 and later. It's used to hold a bracket. So, it's just not present on original 1969s and 70s, but should be expected on all Quadrajets thereafter.

Patrick-------


...including SERVICE carbs for 1968-70 applications manufactured after that time. SERVICE carbs for 68-70 applications manufactured before that time would not have had the boss.

[James B.]

Re: Original vs. Service Replacement Quadrajet

Mark,

I have a 1972 454 & 4-speed. My carb (which I believe to be original to the car) is stamped with #7042217. I also have a service replacement carb for this specific vehicle application (which I had purchased new from GM in the early 80's). If I can figure out how to upload photos to the TDB, I'll post some shots (if it would be of interest).

Jim

[Tom L.]

Re: Original vs. Service Replacement Quadrajet

To add to what James added. While I said I had a 7042220 on my car, it is a replacement dated spring of '72, I forget which month. The correct number for my auto car is a 7042216

[Mike F.]

Re: Original vs. Service Replacement Quadrajet

Do the Service Replacement carbs have the two letter designator stamped after the part number?

I have two carbs for my 70 L-46, a 48 State 7040207 DA (0650) and a CA carb 7040507 (3529).

The 207 is correct, includes the "DA" two letter designator and is dated March 1970 (0650).
The 507 is a correct part number used in 1970, but is a service replacement. It does not have the two letter designator stamped after the part number, it does have the triangle casting and is most likely dated Dec. 1979 (3529).

Besides whatever internal differences may exist between these carbs, the one obvious external difference is that the original 207 carb only has two vacuum ports on the front of it while the 507 has three vacuum ports. The 507 needs an extra vacuum port for the evap canister required on CA cars. My guess is (in my case at least) that service replacement carbs came with three vacuum ports so they would fit any/all 1970 models. All one had to do was plug the un-used vacuum port for the evap canister if not installed on your car.

[Mark E.]

Re: Original vs. Service Replacement Quadrajet

Do the Service Replacement carbs have the two letter designator stamped after the part number?

Good question. I haven't verified this, but my understanding is the two letter code is also on the car's build sheet. It's purpose is to provide a simple two character visual to help line workers locate and install the proper carburetor. If this is true, then there's no need for this code on service carburetors. But who knows, maybe they were stamped anyway.

Can anyone confirm or correct this understanding?

Does anyone have a list showing what the two character codes mean? I've seen explanations for how to decode the PN, but not this suffix code.

[Mark E.]

Re: Original vs. Service Replacement Quadrajet

I have two carbs for my 70 L-46, a 48 State 7040207 DA (0650) and a CA carb 7040507 (3529).

Besides whatever internal differences may exist between these carbs, the one obvious external difference is that the original 207 carb only has two vacuum ports on the front of it while the 507 has three vacuum ports. The 507 needs an extra vacuum port for the evap canister required on CA cars. My guess is (in my case at least) that service replacement carbs came with three vacuum ports so they would fit any/all 1970 models. All one had to do was plug the un-used vacuum port for the evap canister if not installed on your car.

I believe that's correct.

My "correct" 7040205 (1970 LS5) has a connection for the choke vacuum break, and a connection providing full manifold vacuum for TCS. Both of these are on the front of the fuel bowl.

I also have its California version, a 7040505. It has an additional ported vacuum connection on the front of the bowl which I believe is for the evaporative canister.

I also have an unstamped Q-Jet that was on the car when I acquired it. I believe it is a service replacement. It has the same ports as the 7040505, plus a full manifold vacuum connection on the right side of the bowl. This port is used for the AIR system and/or heated air intake system used on some other Chevy models (neither of which exist on the LS5).

[Peter S.]

Re: Original vs. Service Replacement Quadrajet

Peter-----


What's the date on the SERVICE carburetor shown?

Hi Joe,

I do not have the dates for those carburetors as I borrowed that picture years ago from another NCRS member. So I made my own. Here is a 1969 7029207 vs. a service 7029207. Of course there are other immediate tell tales, as the date code for the service carburetor no way could work for a 1969, and the lack of a broadcast code would also be a red flag.

[Peter S.]

Re: Original vs. Service Replacement Quadrajet

FYI, the triangular pad shown became standard on all Quadrajets for 1971 and later. It's used to hold a bracket. So, it's just not present on original 1969s and 70s, but should be expected on all Quadrajets thereafter.

Hi Patrick,

My '75s original carburetor 7045211 YM does not have the triangular pad.

[Patrick H.]

Re: Original vs. Service Replacement Quadrajet

Hi Patrick,

My '75s original carburetor 7045211 YM does not have the triangular pad.

OK, true...
However, a 1975 Quadrajet will not be easily mistaken for any service replacement for an earlier year such as the 69-72s being discussed so far. They look significantly different.

A service replacement for the years discussed so far, yet made later, will have the triangular pad.

[Joe L.]

Re: Original vs. Service Replacement Quadrajet

OK, true...
However, a 1975 Quadrajet will not be easily mistaken for any service replacement for an earlier year such as the 69-72s being discussed so far. They look significantly different.

A service replacement for the years discussed so far, yet made later, will have the triangular pad.

Patrick-------


Yup, a 1975 Q-Jet uses a different float bowl.

[Peter S.]

Re: Original vs. Service Replacement Quadrajet

OK, true...
However, a 1975 Quadrajet will not be easily mistaken for any service replacement for an earlier year such as the 69-72s being discussed so far. They look significantly different.

A service replacement for the years discussed so far, yet made later, will have the triangular pad.

As far as originals though, what years came with the triangular pad? Were you speaking solely to SERVICE quadrajets when you stated, "FYI, the triangular pad shown became standard on all Quadrajets for 1971 and later. It's used to hold a bracket. So, it's just not present on original 1969s and 70s, but should be expected on all Quadrajets thereafter."

So did an original 1972 quadrajet come with the triangular pad? What about 1973? 1974?

[Patrick H.]

Re: Original vs. Service Replacement Quadrajet

As far as originals though, what years came with the triangular pad? Were you speaking solely to SERVICE quadrajets when you stated, "FYI, the triangular pad shown became standard on all Quadrajets for 1971 and later. It's used to hold a bracket. So, it's just not present on original 1969s and 70s, but should be expected on all Quadrajets thereafter."

So did an original 1972 quadrajet come with the triangular pad? What about 1973? 1974?

It appears that 1971-1974 all used the same main body, and therefore all had the triangle pad when new.

All service replacements meant to service these years would have the pad, and I suspect that service replacements meant for earlier years likely had the triangular pad as it made no difference to the remainder of the carb's function. I have a service replacement for a 1970, made many years later, and it has the pad even though an original would not. There was no reason for GM to remove it from the casting after 1971 since the worst that would happen is that it wouldn't be used. The triangular pad continued to be used in the Edelbrock castings, so one would suspect that GM never deleted it either.

1975 changed significantly with regard to shape and appearance of the main body and also added the electric choke.

The point of it all is that the triangular pad does not mean that a carb is, by definition, a service replacement. It just means that the body was made in 1971 or later.

[Peter S.]

Re: Original vs. Service Replacement Quadrajet

Good info - thanks Patrick.