Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem
Fresh engine won't idle
Seff:
Car: 72 Cutlass
Engine: Olds 380 stroker 9.5:1, roller cam, Ebrock performer RPM intake, stock 7a heads with 2" intake valves and a bowl blend port job. HEI off a 403 Olds connected to ported vacuum, set to 19 btdc initial timing.
Carb: 17057253 rebuilt for the old engine, a stock '71 Olds 350 8.5:1. I've just fitted it with an electric choke.
Symptoms:
- Engine won't idle, but will run at 2500 RPM on the top step of the fast idle cam.
- On the second step it runs, but stumbles.
- Off the fast idle cam it dies immediately.
- The GEN light remains on even at 2500 RPM, and the electric choke is slow to open, if at all. (suspect the field terminal is loose, will re-tighten).
- Backfires up through the carb when cranking.
I suspected that the idle mixture was too lean for this engine, so I turned the screws out - no effect. Haven't moved ATP, but that should't hamper idle quality.
77cruiser:
What are the specs on the cam? Was the cam degreed? Did you check for vac. leaks?
Seff:
The cam was degreed by the builder. Didn't check for vacuum leaks, but I'll hook up a vacuum gauge.
Cliff Ruggles:
Pretty hefty cam for the little Old's 380 at 9.5 to 1 compression. The carb will need idle system modifications to make it happy at low rpm's, but that is a nice carb for what you are doing. I use a near identical Pontiac unit on my 455 over 550hp.....Cliff
https://www.youtube.com/watch?v=6zVdoLR-VzM
Seff:
That's a cool video for sure!
I double checked, the final calculated CR was 9.3:1, not 9.5:1. Sorry for the confusion and misinformation. Originally and ultimately the engine is built with EFI in mind in conjunction with a TKO 500 and a 2.56 rear, which is what the cam choice is based upon.
I have the book, is here a recipe in it that describes the idle system modifications needed? It's back at my shop, so I can't check it at the moment.
Thanks.
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