This article is about my experience with calibrating a M4MC Rochester Quadrajet to work properly on the 225 slant six in my 1965 Barracuda.
The Rochester Quadrajet spreadbore 4bbl carburetor has a much smaller, centrally located fuel bowl that seems to work well for off-road vehicles. Since I also had a surplus Rochester Quadrajet that I removed my 1977 Pontiac in November of 1997 (for a propane conversion I completed in January of 1998), I thought I would give it a try in August of 2004. Just bolting-on the carb with its Chevrolet 350 calibration after sitting dry for 7 years, I found that it ran better than my AFB. After a disc brake upgrade that dragged on way too long (several years), I found that my Quadrajet's fuel inlet wouldn't seal and the carb would overflow, likely from a rusty gas tank. I had Specialty Carburetors (SC - Toronto, ON) rebuild it and they switched it from a #77 primary jet to a smaller #72 jet.
After replacing a rusty gas tank in 2015, I ran the AFB again to ensure that any residual rusty silt didn't settle out in my newly rebuilt Quadrajet. On November 16, 2016, I had enough of chokeless cold starts and reinstalled the Quadrajet. After a few tankfuls of gas, I found that, even though I now have a working choke, it was difficult to start in cold weather and it has noticeable lean surge at part throttle.
Specifications about my 750 CFM Quadrajet carburetor:
| Carburetor | Rochester Quadrajet 17057204, M4MC |
| OEM Primary Jets | #77 - 0.077" |
| OEM Primary Metering Rods | #52K - 0.052" [Single Taper (0.052 - 0.046) & Step] |
| OEM Primary APT Turns | ?? - preset from factory, no spec |
| Secondary Metering Rods | CH |
| Secondary Hanger | 33797 |
| Post-rebuild Primary Jets | 0.072" |
| Post-rebuild Primary APT Turns | 3.5 |