Cliff's Quadrajet Parts and Rebuild Kits

Quadrajet Problem Solving => Diagnose a Quadrajet carburetor problem => Topic started by: dc2x4drvr on April 12, 2010, 03:43:45 PM

Title: Too rich at cruise
Post by: dc2x4drvr on April 12, 2010, 03:43:45 PM

Hi,
I can't seem to get my AFR down at cruise, the carb idles at around 13.8, but runs around 11.4 during cruise.
Carb 7041253
Idle Tubes  .033
Upper Air Bleeds  .055
Main Jet  75
Pri Rods  52B
Float Level  1/4"
Mixture Jet Holes  .099
Weakest GM power piston spring
I've tried several jet/rod combinations, and so far haven't had any luck, even tried wiring the secondary air valve closed..
Engine 455 Olds, Torker Intake, 10:1 comp.,headers,4 speed,230/236 cam.
Any help would be appreciated..I've ran this carb for years, but I thought I'd try for a better tune with an LM-1 box.
Thanks  ???

Title: Re: Too rich at cruise
Post by: Cliff Ruggles on April 13, 2010, 04:12:42 AM

The main jets are WAY too large for that carburetor.  Oldsmobile used much smaller jets in the early units, usually around .068-.070". 

The best way to set up one of those early Olds units is to free up the APT screw in the baseplate, and install an external screw.  I'd start with .070" main jets, and metering rods around 43-45 on the upper section. 

Using the APT screw in the baseplate, it will be easy to dial in the part throttle A/F ratio.

If you can't get th APT screw free'd up, change the metering rods to set the part throttle A/F ratio and leave the jet size at .070".....Cliff

Title: Re: Too rich at cruise
Post by: dc2x4drvr on April 13, 2010, 06:02:38 AM

Thanks Cliff, I'll let you know my results..

Title: Re: Too rich at cruise
Post by: Cliff Ruggles on April 16, 2010, 04:04:44 AM

Sounds great!......thanks..Cliff