Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

air filter leaning out afr

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77cruiser:
If I remember right the salad bowl was the best.

Cliff Ruggles:
The Pontiac Shaker assemblies used a very well designed air cleaner assembly.  The lower section dropped some and had a very nice radius guiding the incoming air into the top of the carb.  The lid had a corresponding rise and well designed curve to it.

Years ago I decided to install an RPM intake which was just over 1" taller than my factory intake. This required going to a 1" shorter air filter and moving the lid 1" closer to the carburetor. 

With that set-up the engine idled fine and drove perfectly.  However going quickly to full throttle there was a HUGE stumble/hesitation/bog, which cleaned up after a couple of seconds and the engine pulled hard to the shift point. 

I removed the lid and the problem went away.  Then I tried an X-Treme lid and SOB it stumbled just like the stock lid....hum?  I ended up making a custom air filter assembly for the Shaker opening and sealed everything else off running nothing over the carb at all.

I did some track testing and eventually went back to the factory iron intake and all the stock height air filter and Shaker parts.  It proved to be a very good set-up running just as quick as the taller RPM intake with all the "cobbling" to make it work. 

To this day I don't know why the XTreme lid didn't work as one would think it would equally as good as running nothing over the carb at all.......

Charlotte1:
Hello Everyone
A small update. I have re installed the 1” drop base that I originally had noticed the afr change.
This air cleaner assembly definitely seems to lean out things. So I’ve tried an experiment. I put duct tape across the front of the air filter element. On the outside of the element. The tape is approx 7-8” long and covers approx 2.5-3” of the 4” element.
And funny enough, with that setup, it seems to richen the afr back to where it’s close to the readings where the air cleaner was off and tuned at. So not too bad.
I’m going to check to see if I have the hood clearance and if I do( I think I do), I’ll try a flat air cleaner base and a 3/4” raised base. With flat base, I might have to use my spacer.
It’ll be a few weeks to get the parts to me but I’ll post back with my findings.
 

Frank400:
looking forward to hear about the results...

Jeff K:
I use these.. They sell them on e-Bay. They keep the hot air coming off the radiator from going into the carb. The first time I saw one was on Zora Duntovs Corvette at the Custom car show at Pittsburghs new Civic Arena.. He was such a humble dude. Taking the time to answer questions, you could see he truly loved talking cars.

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