'68 carburetor question

[Guest dcdpgh]

Dumb question,

In my quest to purchase a carb kit for my Rochester Qjet carb I found the number 29240MD 3328 stamped on it. I believe, but have no way to confirm, that it is the correct and original carb. Some reference material I have (Cars Inc.) and the auto parts store both say a correct number for my '68 would be 7029240. Do these two numbers match, and if so what is the significance of the "70" in the catalogs, and the "MD" & "3328" on my carb?

Any ideas?

[bob71GS]

Dan,

You should have Q-jet 7028240 for your 68. The Rochester number decoding is 702= 1960's Rochester Carbs 76 and later will start wi <img src="http://forums.aaca.org/images/graemlins/smile.gif" alt="" />th 170, 8=year produced 1968.2=Quadrajet 4 bbl.4=Buick 9=auto trans. 7029240# would indicate a card for 1960's for a 1969 4bbl Buick with auto trans. The last digit even #'s auto trans, odd #'s manual trans.

Bob Bonto ROA # 277

Technical Advisor 71-73

[Guest dcdpgh]

Thanks Bob,

I still a little confused. Am I looking in the right spot for the carb number? The numbers I found were on the driver's side of the carb in vertical arrangement, reading bottom to top. Based on what you've said does that mean I have a '69 carb on my car?

Sorry for the dumb questions.

[RivNut]

Your are correct, the vertical numbers identify your carb as a 1969 model. The 3328 means that the carburetor was built on the 332nd day of 1968; that would be about the first of December, definiately in the 1969 production year. The MD identifies the plant in which the carburetor was built.

[Guest dcdpgh]

Thanks guys,

At least I know which carb kit to buy. Anybody's guess why the original carb is gone.

While we're at it let's have some fun with numbers. I was able to decode most of the firewall tag from the helpful info on the ROA webpage. Trim 683 means Strato Bench interior in Buckskin (which matches car), Paint X2 means Buckskin with vinyl roof (which matches car), and 68-49487 means 1968 model Riviera body. What I don't know is what "09C" in the upper left corner means, and "EUC031743" means next to Body, just right of 68-49487. Also - how do I find the VIN on the engine block and tranny, I know there is a way.

I know, lots of questions. Thanks for the help so far.

[NTX5467]

The orig carb could have had some "issues" (whether from production defects or from an overstrong technician changing the fuel filter, for example). That was still pretty "young" in the QJet's life so not everybody might have known how to work on them at that time--possibly. Or the car might not have "run to suit" the original owner who complained enough that a new carb was installed under warranty or whatever. I recall some QJets produced by Carter Carb Co generally had more problems than normal QJets made by Rochester Products (GM), but I don't know if the Carter-produced QJet might have been on your vehicle when it was new.

If it was changed under warranty (or at the shop's expense at the dealership, possibly), the replacement carb for the original production part number could well have been the production carb for the (then-new) 1969 model. Back then, there typically were not that many changes to the next-year's new models so the 1969 carb would have been a bolt-on situation for your 1968 car.

Now . . . IF your intake manifold has the "heat track" cast into the carb mounting pad (as my '68 Buick Chassis Service Manual illustrates for the 430 V-8), on the primary side of the pad, it'll need the "two-part" carb base gasket--a stainless steel shim that will go against the bottom of the carb directly and a composition gasket that will seal between the stainless steel shim gasket and the carb mounting pad. It takes BOTH to make things work and the stainless steel gasket does go directly against the bottom of the carb . . . and it does not have a vacuum leak (provided it doesn't have any kinks in it, I suppose). The heat track is there to aid cold weather driveability as it circulates exhaust gases from the heat crossover in the intake manifold's center section. The Fel-Pro number for the composition gasket (which I bought for my '68 LeSabre 350, several years ago) is 60001 (80262), which "Replaces 1378509" (which looks like the GM part number for that particular gasket . . . at one time). Finding the stainless steel gasket might be a little problematic, though, as not everybody knows about it (especially less vintage parts counterpersons, with all due respect). I got these items from the local NAPA store, at that time. I think that 1968 and 1969 would have been the same, but GM stopped using the "heat track" setup for 1970? In general, the stainless steel gasket is reuseable, provided you don't put some bends in it, so be gentle in getting it cleaned up for reuse. I know they are still available, though as "5563" just put a QJet set-up on his '63 Wildcat and they sent one of those gaskets along with it.

Just some thoughts,

NTX5467

[Guest dcdpgh]

Thanks guys for the responses. I really appreciate your willingness to share your insights and knowledge.

[RivNut]

Dan,

Is the carburetor not running correctly to suit you or are you just wanting to make sure that you've got a correct "numbers matching" car and components. See if you can find a shop manual somewhere or some carburetor books and identify what the differences are in the two carbs. I have a 1964 Riv with the 425 engine. I bought an original carb that had a factory rebuild for a 1964 with a 401 engine really cheap. The carb works great. The only difference between this carb and the one for a 425 is something like .00002" difference in the size of the rear jets. I really doubt that I could tell the difference between the correct one and the one I have.

If the carb isn't working correctly and you need a new one, then searching for the correct one would be worth it. I seriously doubt if you'll find any significant difference between the 68 and 69 carbs as long as they both came from 430 motors.

Here's where to look for ID numbers for 400, 430, 455 engines from 1968 on -

The engine serial number is between the two front spark plugs and the left exhaust manifold, and the production code number is between the two rear plugs and the exhaust manifold, also on the left.

Who knows, you might have a complete 1969 motor in your 1968?????

[Guest dcdpgh]

Hi Ed,

I don't think I need a new carb, we just want to tighten things up abit. I just didn't expect to find a '69 carb on the car when I went shopping for a carb kit. I just aquired the car in January and have spent the past few weeks "going thru her" to get ready for spring. This was one item on the list.

Thanks for the tip on ID numbers. She's got a matching engine alright, serial number matches the dash VIN. The production code was "048" (right next to the dipstick hole), does that mean April 1968? Also between the two rear spark plugs was "PD", would that be plant location? Any insight on the firewall tag numbers from my other post?

[68RIVGS]

Dan- Your carb is a '69 Buick 430, non Riviera type. Carter manufactured Quadrajet carbs for Rochester, and they used a different numbering system from Rochester.

PD is the correct '68 430 engine code, and 048 is the time built code.

The ST400 tranny will have a plate attached (passenger side) with a BT--- (3 digit date code).

On the firewall Body Number Plate -

09C is the time built code, and EUC------ is the Assembly Plant, and Fisher Body Number.

Most of this info is also available in the '68 Buick Shop Manual, if you don't already have one Dan - it is a very good investment, and also a great way to get to know your Riviera !

[Guest dcdpgh]

Thanks for the follow up Randy.

I do intend to pick up a '68 Shop Manual, just haven't gotten there yet. I really appreciate all you guys help in the meantime.

[Guest dcdpgh]

Randy,

I just went back and re-read your response and realized I missed something you said the first time I read it. Are you suggesting that I have a Carter built Rochester Qjet based on the "70" missing from the start of the carb number? My carb definetly has the Rochester logo stamped on the side of it, and it looks every bit like a Rochester. Is it an imposter? Does the fact it is 29240 and not 7029240 mean something? Would a carb kit for a 7029240 be right for this carb?

Ideas?

[68RIVGS]

While that's a possibility, it's not likely in your particular case Dan.

Carter built Rochester Q-jets state that in cast letters at the top of the flat surface just by the vertical part no., in addition to the Rochester Q-jet logo cast on the same surface.

(I have one from a '68 Riviera parts car).

Your 29240 no. ID came up as - '69 Buick 430 4bbl Automatic, 'all except Riviera, OEM# 7029240.

I'm sure a 7029240 kit (if available), will suit your requirements !

[Guest dcdpgh]

Many thanks again Randy (and all).

[68RIVGS]

You are most welcome - anytime Dan.

That's part of what this great hobby, and ROA is all about - Sharing the Pride !

Along with a little knowledge, experience and expertise.

[Wurstfreund]

Hello from Germany, and sorry for digging out such an old topic...

 

I`m on the search for my thermal Problems on my 68 Riviera, and eliminated nearly anything beside the carb and the radiator itself.

Following the lead that in the last 50 years someone may had mounted not the right carb, i ask for your help.

My car, of course a 430, is equipped with a 7028244 Qjet. Does this match with the car/engine?

 

When searching this number with Carbs Unlimited, i get as feedback that this one was in use for a 350 LeSabre/Special, but not a 430 Rivi.

Halp! Thank you!

 

Best,

Markus

 

 

[carbking]

From my website:

 

1968 Buick carburetors

 

 

     1968     6   250 A/T                           Rochester  MV             7028014                   2454

     1968     6   250 S/T                           Rochester  MV             7028047                   2455

     1968     8   350 A/T                           Rochester  QJET           7028244                   1820

     1968     8   350 A/T                           Rochester  2-GV           7028140                   2456

     1968     8   350 S/T                           Rochester  2-GV           7028141                   2457

     1968     8   350 S/T                           Rochester  QJET           7028245                   1819

     1968     8   400 Early A/T                     Rochester  QJET           7028242                   1821

     1968     8   400 Early S/T                     Rochester  QJET           7028243                   1821

     1968     8   400 Late A/T                      Rochester  QJET           7028246                   1818

     1968     8   400 Late S/T                      Rochester  QJET           7028247                   1818

     1968     8   430 Early A/T                     Rochester  QJET           7028240                   1821

     1968     8   430 Late A/T                      Rochester  QJET           7028248                   1818

 

Jon.

Edited July 28, 2021 by carbking (see edit history)

[EmTee]

I was hoping that Jon would chime in on this one! 

[Wurstfreund]

16 hours ago, carbking said:

From my website:

 

1968 Buick carburetors

 

 

     1968     6   250 A/T                           Rochester  MV             7028014                   2454

     1968     6   250 S/T                           Rochester  MV             7028047                   2455

     1968     8   350 A/T                           Rochester  QJET           7028244                   1820

     1968     8   350 A/T                           Rochester  2-GV           7028140                   2456

     1968     8   350 S/T                           Rochester  2-GV           7028141                   2457

     1968     8   350 S/T                           Rochester  QJET           7028245                   1819

     1968     8   400 Early A/T                     Rochester  QJET           7028242                   1821

     1968     8   400 Early S/T                     Rochester  QJET           7028243                   1821

     1968     8   400 Late A/T                      Rochester  QJET           7028246                   1818

     1968     8   400 Late S/T                      Rochester  QJET           7028247                   1818

     1968     8   430 Early A/T                     Rochester  QJET           7028240                   1821

     1968     8   430 Late A/T                      Rochester  QJET           7028248                   1818

 

Jon.

 

 

So, having a 7028244 in my `68 430 Rivi seems not to be the perfect match... Like in real life.

Which one to choose, where to get it? I want to keep the car original as possible, no fancy conversions. Or should i...?

Thanks a lot!

[telriv]

Markus,

 

    As to your thermal problems. Since you are having thermal problems it could be the carb. since it was originally for a 350 carb. the engine is running extremely lean being it was originally for a 350 carb.  Its not normally in the capacity of most to make the nec. mods besides jets & metering rods.

    So taking to the list Jon provided you only have a choice of two, early & late.  So you need to do a little research to determine IF your vehicle is early or late.  Part of the nec. info is on the tag, aluminum plate attached to the firewall, that has the build date on it. Your next question is that does this info early or late.  Next is the number stamping for the actual carb. build date to match the vehicle build date of the carb. which can be up too one week or four months before the actual build date of the vehicle.

   Can you understand what I have said???

 

Tom T.

[carbking]

Markus - there are considerations, and then the final decision becomes yours.

 

First discussing the early and late 1968 8-430 carbs (7028240 -> 7028248). The only difference in these carbs is that Rochester made a modification to the float to improve fuel control; all calibrations are identical. So from a purely practical standpoint, the 7028248 would be the best carburetor to use. However, if you do not regularly drive in city traffic in temperatures approaching 35 degrees C., then the 7028240 would probably work equally as well.

 

When was the change effected? I do not know. The Rochester documentation only shows early-late, no date or serial numbers. If Buick were as meticulous as Pontiac, then somewhere there is a Buick Service Bulletin that states "effective with serial number xxxxxxxxxxxx Rochester 7028240 was replaced with 7028248". I have a virtually complete set of Pontiac Service Bulletins, but zero Buick Bulletins.

 

There should be 4 additional numbers in the same area as the part number on the carburetor. This is the "date code".

 

These four digits are in the format "jjjy" where jjj are the three digit julian day, and the y is the last digit in the year.

 

Thus a date code of 3657 would decode to the 365th day (December 31st) of 1967.

A date code of 0018 would decode to the 1st day of January 1968.

 

If you are building a numbers-matching show vehicle (you state you wish to keep it as original as possible), date codes are important. Conventional wisdom is that the date on accessories such as the carburetor should precede the build date of the vehicle by from two weeks to ten weeks.

 

(If you don't care about matching numbers, then the date code information can be regarded as extra, unnecessary trivia).

 

Where do you get either? Again, I do not know; I am sold out of both, and no longer buying carburetors.

 

You have a third option, but I do not suggest it, merely stating that it is possible.

 

If you can locate someone that is well-versed in the modification of Rochester Quadrajets, the 7028244 you currently have, may, at great expense, be modified to think that it is a 7028248. There would be many expensive parts to be replaced, plus some machine work. Again, this is an option I would not suggest.

 

As far as other options (different brand of carb, etc.), will leave these alone, as all of them will require engineering (modified fuel line, modified air cleaner, etc., etc., etc.). Simply not worth the effort in my opinion for a basically stock engine.

 

Jon.

Edited July 28, 2021 by carbking (see edit history)

[Wurstfreund]

Hi Jon, Tom,

thanks a lot for your info. My 7028244 got a date code of 2107, but as this carb is already out of discussion anyway, this is just trivia.

Finding a Rochester specialized magician here in Germany is nearly impossible. No well-versed people around here, and i dont want to finance someones freshman years into Rochesterology around here, to be honest.

I`m not fixed to the QJet, and my Rivi is far away to be a matching number winner, but i have this sort of fetish to have the car as close as possible as it was once manufactured.

 

I know that the answer will be "it depends", but which of the possible replacements come closest, knowing that the Riviera is a Gentlemens Car and not a Quartermile winner?

Stable, Solid, Stock Performance...

Should i change to a Weber assembly? Just kidding  🙂

Thank you!

 

[RivNut]

If you can find this book, you can probably do most everything yourself except any machine work that might be required.  Author is Cliff Ruggles.

 

https://smile.amazon.com/Rebuild-Modify-Rochester-Quadrajet-Carburetors/dp/1932494189/ref=sr_1_2?dchild=1&keywords=rochester+quadrajet+cliff+ruggles&qid=1627496818&sr=8-2

[NC1968Riviera]

On 7/28/2021 at 1:39 PM, carbking said:

I have a virtually complete set of Pontiac Service Bulletins, but zero Buick Bulletins.

I have a full set of 1968 Buick Service Bulletins. I will look to see if any mention the carburetor update. 

[NC1968Riviera]

On 7/28/2021 at 1:39 PM, carbking said:

Rochester 7028240 was replaced with 7028248

Sometimes these particular carbs (as well as the 69 430 carbs) show up on US eBay Motors. 

[Wurstfreund]

I check regulary ebay US for the right carbs, but either they look like an ancient atrifact or the seller is refusing to sell overseas (Germany). Nevertheless it would be a magic back, not knowing what i will receive...

Are there any shops or trustworthy sources, selling the real thing?

 

Another question: Was it common practice to replace these carbs with ones for smaller engines, like in this case taking a 5,7l carb into a 7,0l engine?

Just asking, as i have contact to another Rivi owner in Germany, having exactly the same issue. Replacing the carb with the right one solved the thermal problems in this particular issue.

Thanks for your help!

[carbking]

Wurstfreund - ALL Rochester Quadrajets manufactured before 1970 were the same size, 750 CFM.

 

What is different are linkages and calibrations (fuel jets, air jets, bypasses, metering rods, rod lift, etc.).

 

A really good rule on post-1967 carburetors is to ALWAYS use the correct original carb for the engine. Carburetor gurus with a really complete machine shop can ignore this statement.

 

As far as shipping to Europe (or anywhere else other than the country of origin):

 

There are many really good reasons for a small company NOT to ship outside the country of origin, ESPECIALLY during the pandemic. We do not ship outside the USA, but we have MANY European REPEAT customers that have us ship to a mail drop in the USA, and the package is then forwarded to its destination. Perhaps this would be a solution for you.

 

Jon.

[RivNut]

Rockauto.com shows a rebuilt carb for the 68-69 Riviera. They do not ship overseas but reference shipping to companies that will handle overseas shipping. There are other companies showing this carb as available.  I just Googled ‘Rochester 7028240’ and found quite a few references.  

Edited August 1, 2021 by RivNut (see edit history)

[jj5794]

Dan,

 

As you may be aware, Car-Part.com -"Used Auto Parts Market" is a very helpful resource to check inventories of salvage yards, at least in the US and Canada, for specific parts. 

 

Five carburetors are listed In Car-Part.com for the 1968 Buick Riviera.  Two of these are specifically annotated as 7028240 and these are from the same WA salvage yard.  These others do not list a part number.

 

Hope this may help.

 

Jim Vesely

ROA # 7437

BCA # 39477