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Model Number 7041250 is a 1971 Oldsmobile 350 engine Rochester Quadrajet 4bbl carburetor. I run a 1971 Oldsmobile 455 engine Rochester Quadrajet 4bbl carburetor (7041251)on my 350 engine. I can't recall the 1971 Oldsmobile 350 engine Rochester 2 bbl carburetor Model Number. Sorry
Thank you sir : ... is that carb used on 455 versions as well ? I just found a page that says the “1” as the last digit is for a manual tranny does that not mean a lot
Last edited by Mike71cutlass; July 18th, 2020 at 02:19 PM.
...is that carb used on 455 versions as well ? I just found a page that says the “1” as the last digit is for a manual tranny does that not mean a lot
Is what carb used on 455 versions? I know the one I identified above as 7041251 was used on the 455 - which is what I indicated, already. Now, whether or not the "1" is attributed to a manual transmission I cannot validate. There are others who can provide more accurate information. I thought (perhaps mistakenly) Rochester employed various numbering formats for various production model years based upon their relationship with Rochester and the vehicles upon which those carburetors were installed. I'd have to research (a lot) to find the information you're asking regarding the number "1" (someone else knows for sure). I do know this however. There were differences in carburetor design based upon usage with an automatic transmission and a manual transmission. If I recall correctly, there were two main differences (don't hold me to this): (1) carburetors have an inherit idle passageway (circuit) design (I believe this was to accommodate deltas between manual and automatic transmission application?); and, (2) primary and/or secondary jets varied depending upon manual vs. automatic (including size of engine), as well. Someone will "surely" correct me and add to this.
Last edited by Vintage Chief; July 18th, 2020 at 02:41 PM.
Reason: sp
Thank you sir : ... is that carb used on 455 versions as well ? I just found a page that says the “1” as the last digit is for a manual tranny does that not mean a lot
Once again, do NOT believe everything you read on the interwebs (or from Cliff Ruggles, who seems to be the one perpetuating this myth). The Odd/Even for AT/MT may be a Chevy thing (I have no expertise with belly button motors), but it most certainly does NOT apply to Oldsmobile. You can see from this list (which comes from the 1971 engine assembly manual) that the odd/even thing is total BS. Other years are similar.
The 7041250 even numbered carb was used on every single 4bbl 350 engine built by Olds in the 1971 model year, no matter what trans was used.
The 7041251 odd numbered carb was used on every single 4bbl 455 engine installed in a RWD Olds for the 1971 model year except 442s, no matter what trans was used (and since that primarily covers the full size cars, nearly all of them had automatics).
The 7041252 even numbered carb was used on every 1971 Toronado, all of which were automatic
The 7041253 odd numbered carb was used on 1971 442s (non-W-30) with manual trans
The 7041256 even numbered carb was used on 1971 W-30s with manual trans
The 7041257 odd numbered carb was used on 1971 442s and W-30s with automatic trans
Once again, do NOT believe everything you read on the interwebs (or from Cliff Ruggles, who seems to be the one perpetuating this myth). The Odd/Even for AT/MT may be a Chevy thing (I have no expertise with belly button motors), but it most certainly does NOT apply to Oldsmobile. You can see from this list (which comes from the 1971 engine assembly manual) that the odd/even thing is total BS. Other years are similar.
The 7041250 even numbered carb was used on every single 4bbl 350 engine built by Olds in the 1971 model year, no matter what trans was used.
The 7041251 odd numbered carb was used on every single 4bbl 455 engine installed in a RWD Olds for the 1971 model year except 442s, no matter what trans was used (and since that primarily covers the full size cars, nearly all of them had automatics).
The 7041252 even numbered carb was used on every 1971 Toronado, all of which were automatic
The 7041253 odd numbered carb was used on 1971 442s (non-W-30) with manual trans
The 7041256 even numbered carb was used on 1971 W-30s with manual trans
The 7041257 odd numbered carb was used on 1971 442s and W-30s with automatic trans
joe, reviving an old thread here. do you know what the difference was between the 7041253 and the 7041256 carbs? my '71's been upgraded with w-30 stuff. i have a 7041253 on the shelf. i was wondering what, or if it was worth, making conversions inside it as well. thx, mb
joe, reviving an old thread here. do you know what the difference was between the 7041253 and the 7041256 carbs? my '71's been upgraded with w-30 stuff. i have a 7041253 on the shelf. i was wondering what, or if it was worth, making conversions inside it as well. thx, mb
Well here's a mystery. the '1256 carb isn't listed in the Big Book 'O Carburetors.
Interestingly, it also isn't shown in the 1971 CSM EXCEPT in the applications table on page 6M-50. All the other adjustment tables in the carb section of the CSM do not list it. Let me check the service bulletins to see if there's an update. The Carb Book is where I get the jetting data.
I recall reading this thread years ago when I joined & bought my '71 CS convertible.
The OP of this thread has owned several W-xx models. I don't know this member.
They never made the 7041256. Some of the earlier 71 manuals were printed before the GM bulletin,stating that the 7041253 would be used instead. If you ever see a 7041256,it is not real.
I'm only a messenger, here is the URL link to his post >>> 5
Located below (URL link) is a serious quandary related to this mystery, posted by someone who evidently has some serious years of experience w/ Oldsmobile products.
The 0256 is rare & limited (as are the W-xx's they were mounted on) but it's not remarkable such as the 1256. It's readily listed in all documentation.
Last edited by Vintage Chief; June 7th, 2024 at 04:38 PM.
Reason: sp
While I suspect this GM carburetor compendium is not 100% exhaustive, it's the best legitimate documentation I've found anywhere (w/o owning Joe's 100lb bound book) - each available for d/l.
I stumbled upon this site too, https://tiptopgarage.com. I was able to get to see Delco bulletin's for carbs, like the example shown, which shows differences between the carb numbers. It didn't list the 7041256 though, so I can't see that difference.
July 18th, 2020 | 01:55 PM
