Hi all,

Considering a rebuilt carb for my 76 cutlass. One rebuilder who seems knowledgeable indicated the 76 carbs are problematic with the aneroid, and suggested using a 77 carb instead. The carbs are almost identical but the 76 has two ports coming out the back (up high near the secondaries) while the 77 only has one port. Does anyone know what the second port was used for on the 76 and why the 77 doesn't have it? One of the two ports (passenger side) is used for the hot air choke connection, but I have not been able to find the use of the second port (on the left/drivers side). I know I need to buy a service manual.

Thanks!

p.s. I attached a pic showing the two ports on my 76 carb.

 

Both of those are fresh air ports. One for the choke as you mentioned. I don’t know what the other would connect to, but if you need it connected, just use a T on the single port of the 77 carb.

 

Yes, you do.

 

Are you sure that is a factory original 1976 quadra jet? these pics are of mine when i was rebuilding it showing only one port in the rear and a large port drivers side in the front.im pretty sure 76 was a one year only carb which had a secondary power piston .I read avoid these carbs for a rebuild due to that .my car is a factory non ac car so that could have something to do with the porting (not sure).i can say i did a successful rebuild on mine and it works well i tried screwing around with jetting but ended up with all the originals back in it.Im interested to hear any info on these years by someone more knowledgable than i.this thread is a month old so you maty have it sorted out by now

 

Edit: Missed a couple the first time.

First, there were NINE different Qjets used on 1976 Cutlass 350 cars. Which is yours?

17056250 - 49 state, AT, non-A/C, early
17056253 - 49 state, AT, A/C, early
17056256 - 49 state, AT, A/C and non-A/C, early
17056550 - Calif, AT, non-A/C, early
17056553 - Calif, AT, A/C, early
17056556 - Calif, AT, A/C and non-A/C, early
17056551 - Calif, AT, non-A/C
17056258 - 49 state, AT, non-A/C, late
17056259 - 49 state, AT, A/C, late

The Calif carbs have different jets, metering rods, choke assembly, and fast idle cam from the 49-state carbs. The air horn is also a different part number on the Calif carbs. There are even more variations for the 1977 carbs.

 

Hey - thanks for your response. I'm not 100% its my original carb but I think its likely as the date code is close to my cars build date. My car was built July 76 (pretty late for a '76) and the carb date is somewhere around 1806 - so about June 30 which aligns.

I found this example on ebay of your carb (17056256) and they list is as a 78+ carb FWIW. I thought the middle "6" in your number would indicate a 76 model year so maybe the ebay listing is wrong but the front of this carb also looks more like your carb and less like my carb.

Rochester carburetor 17056256 1978-79 Oldsmobile 360; Eng. a/t | eBay

Also here's another carb on ebay with my # and it lists it as '76 Cutlass 350 which is right for my car:

Rochester Quadrajet 4-Barrel Carburetor 1a 17056259 800 CFM 1976 Oldsmobile 350 | eBay

 

The "6" does indicate 1976, and yes, the listing is wrong. Imagine that...
They also say it's for an "Olds 360", so there's that.

Also, be wary of mass rebuilders. They can't afford to stock the wide variety of different carb numbers for each year and typically will list their rebuilds as covering multiple years. They may be "good enough" to get the car running (and likely light years better than the crusty old one) but they won't be really correct.

 

Joe ,your listings show for a 350 olds . my car has its original 455 in it and what i thought was the original carb was the 455 a different number? To the op i don't mean to hijack your thread i apologize in advance

 

From the big book o' Rochester:



Now, as I look further, both '251 and '256 use the same jets and primary and secondary metering rods, so perhaps this is a typo?