Rusty Bowtie
General Category => General Discussion - Intros => Topic started by: 28chevyguy on June 10, 2020, 09:59:29 AM
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Im trying to tune the Edelbrock AVS Carb on my Oldsmobile 350. (probably going back to the Quadrajet soon)
This carb has adjustable secondary . So The car runs and drives OK . Breaks up when you get on it , If you really try to force it through you get a backfire through the carb. Is this usually lean or rich? I thought it might have been lean so I tightened up the secondary a bit more , seems like it makes it backfire more easily now . Going to pull a plug when it cools down. last night I tried advancing the timing a tiny bit for experiment It seemed to backfire through the carb easier. That made me think it was lean, so I tightened up the secondary this morning and still same thing. Does bogging and backfiring through carb usually mean lean?
I also have one more adjustment click on my accelerator pump if it turns out to be a lean condition . I need to look into a cheap wideband diagnostic tool , theres got to be something good and affordable out there by now.
update: Just moved the accelerator pump linkage from the middle (stock setting) to the richest setting . Seems like it bogs and backfires through the carb even more I'd say. Not sure whats going on . Plugs didn't seem sooted up really, a little white looking around the electrode and ceramic tip. Starting to think Edelbrocks are just a joke .
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Did the car run good before the carb swap or other mechanics? My first thought is you have an an accelerator pump/diaphragm problem...is it squirting fuel in steady stream..or is is weak.
Also if you have a water bottle...squirt some water around the carb base and "intake manifold to head" joints running. Listen for it sucking in water or it begins to stumble.
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Yes the car ran fine with the Rochester, I thought I had a carb problem but it ended up being ignition, if I can't get this thing to run right I'll just throw that Quadrajet back on. I'll check the Stream of the accelerator pump.
Update: Night mare is over I think, edelbrock tech informed me this AVS carb is set up out of the box for hot cammed applications with very low vacuum , my olds motor is stock cam high vacuum - so I need a stronger spring set otherwise the secondaries will never work.
Ordering the kit now , $10 and I'll be able to do burnouts again !!
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shouldn't that be WEAKER SPRING SET, for vacuum secondaries with low vacuum. Stronger spring set doesn't make sense.
Other alternative for low vacuum is to install a SSBC vacuum pump which produces 18--24" of vacuum. Because if you have power disc brake system you need strong vacuum to operate the brakes..
I have it on my 35 coupe with 350 zz4 and hot cam , plus phaeton SP383 with more lift and duration than a hot cam kit.
mike...................HAIRBALL
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my car makes high vacuum with a stock cam. The carb out of the box wants lower vacuum cammed application.
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What vacuum does the AVS carb like?? did the tech give you a range for the vacuum...reason I'm inquiring I have a friend wanting to put AVS carb on a motor and I wasn't aware of the vacuum requirement for this carb
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I believe they want 9-10 lbs , they come out of the box with the orange springs. I need to install the silver ones.
Edelbrock spring kit 1464 .
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how much "inches of vacuum" is your motor producing at idle ???????
Use a vacuum gauge to determine the exact figure.
My 350 ZZ4 with gm hot cam kit and 1.6 roller rockers, produces 12" max.
It would not work the power brakes booster, felt like manual brakes.
mike