Old'Lass

Hello,
I have read many of the posts on engines and carbs related to my 1970 Cutlass Supreme Convertible. Its VIN prefix/model is 3.42.67.0.E, which I think translates to Olds.Cutlass.Convertible.1970.NewJersery.

It has the 395558 block. The car also has a 4bbl 7041251 Quadrajet, with an "RC" and "0471" stamped afterwards. I think this is the carb for a 1971 455, not a 1970 Cutlass Supreme Convertible, which I think should have been equipped with an OEM Quadrajet 7040250.

Am I right about the mismatch on year and motor/carb? What are the effects of using this carb?

Thanks.

P.S. This car has been sitting for 25 years. Before that I drove it occasionally for ten years and put about 15,000 miles total on it. The motor was rebuilt in Florida before I drove it to California 30 years ago, with factory air keeping us cool all the way across Texas in August. The carb may have been swapped at rebuild, but I don't remember that line item being in the rebuild.

Fun71

My 70 Supreme had a 71 carb on it when my Dad bought the car as a second vehicle in 1977. Not sure why - maybe it was a repair thing when the car was new(er)?

Anyway, I doubt the engine will notice much (if any) difference in the carbs. The real check would be the jets and rods, as in are they correct for the 71 455 carb or the 70 350 carb?

Below is the info I have on the rods and jets:

Year & Application.....Carb #......Main Jet.......Primary Rod............Secondary Rod
1970 350...............7040250....7031970....7040701- "52C"....7033658- "AT"
1971 455...............7041251....7031970....7034849- "49B"....7033104- "AK"

joe_padavano

Ken is correct. The 7041251 is a 1971 455 carb and has certainly been replaced. A prior owner may have done this in the misguided attempt to get more performance or just as an expedient way to replace a carb that needed rebuilding. The good news is that the Qjet is sophisticated enough that despite the incorrect metering parts, the car will still likely run acceptably. In fact, with today's ethanol-laced gasoline, richer jetting may just get things back to where they were supposed to be.

joe_padavano

You need to swap with this guy who is running a 7040250 carb on his 455 in a Supreme.

https://classicoldsmobile.com/forums...ajet-carb.html