Q-Jet Queries

TMar365

Not-quite-so-new-guy
Apr 8, 2020
5
1
It's a few years, like 15 since i rebuilt my Quadra-junk. I believe you have to set the metering rods with a dwell meter, if memory serves me right.
Now i remember, lol, green test wire to positive lead on dwell meter, black lead to ground. You'll be looking for 32 to 35 degrees dwell on the 6 cyl scale.
 
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airboatgreg

Royal Smart Person
Oct 2, 2016
2,042
113
Check to see if you have vacuum on the carb vent line when you rev the engine up. You may have a faulty cannister purge valve
 

gmtofd

Not-quite-so-new-guy
Oct 30, 2015
24
3
It has already been mentioned that the single wire O2 sensor will not get hot enough because the headers don't retain heat like the cast iron manifolds so the computer cycles back and forth between open and closed loop or stays in a limp home mode. A heated sensor needs to be installed. I've been through this run rich after header install on CCC controlled engine twice. The first time was with a GP that had a LG4 engine. Installed long tube headers, O2 sensor fitting welded in the collector and from the first of the key, I knew there was a problem. A heated sensor improved the run rich problem. Done a 350 crate motor swap on my daughter's '87 MC/SS, used Edelbrock shortie headers and with the single wire sensor, it never ran right until installing a heated sensor.

Also, your feedback carb will have to be somehow qualified to make sure that it is working correctly, not leaking internally, but that is easier said than done. The best way to check out the carb is to mount it on another known running good OBD 1 CCC controlled Chevy engine. As mentioned 21 years after GM used CCC if will be hard to find a willing donor.
 
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