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Old 11-01-2012, 01:22 AM
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Interesting fuel problem

I have a 454 mildly built big block and the air/fuel gauge is dancing all over the place. At Idle it is stable and rich but as soon as the throttle opens it drops off the charts lean. If you cruise it just right it will come back up to rich/ideal but it flutters everywhere. Very delicate foot play is required to make have a stable Ideal ratio. If you hit it some, it goes off the charts lean again. If you really hit it, she pops through the carb. Also, ive got duel tanks and the problem gets worse when I use the right hand tank. The carb is a holley 570 street avenger and there is no way I know to adjust the float level. If I had to guess Id say it needs a bigger fuel pump. I also started to think maybe the tiny 6x2 paper air cleaner inside my scoop is too small and preventing the carb from working properly. The fuel pump and carb both worked flawlessly and I never had any lean issues before I added the roller cam and summit street scoop. Maybe it is something totally different like a vac leak or timing but Im %99.9 its all good. Anyone else have a dancing air/fuel gauge???

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Old 11-01-2012, 05:04 AM
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hows the acell pump?
is it dead,/ripped sounds like it..
a back fire through the carb will kill a powervalve if there is no check valve(ball)

I'd look at the accelerator pump and power valve if the carb is a holley.. as you left that out..
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Old 11-01-2012, 06:32 AM
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Interesting fuel problem

Since you switched to the roller cam sounds like the carb is too small. I have never heard of someone using such a small carburetor on a 454. I heard of a 650 DP being used. If it is fine at idle then try going up two to 4 jet sizes. Have you used a vacuum gauage to adjust the carburetor? Check float adjustment. What is your carburetor List # located on the right side of the air horn. Here is your instructions for your carburetor. It will explain how to adjust the floats, idle mixture screws, curb idle screw, and fast idle screw. http://www.holley.com/data/Products/...0219-3rev3.pdf Here is another article on distributors and timing. It also has how to set up a Holley carburetor's transfer slot to have the correct idle when sstarting the motor. it explains how to set your timing also. http://www.crankshaftcoalition.com/w...EI_distributor Also try installing a 14x3 air filter & base to see what kind of readings you get then.

Last edited by cdminter59; 11-01-2012 at 07:00 AM.
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Old 11-01-2012, 02:12 PM
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May the torque be with you.
 
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Thanks everybody for helping

Thanks for the help, Im messing with it some more today. It drives ok but is far from optimal. Removing the air cleaner helped a lot, no more backfires and pops at WOT. The 14x5 filter is due tomarrow. It does bog in the middle, but once it catches itself then it screams power. I have the spring assortment for the secondaries, I think the bogging is because of secondaries opening too soon??? Still goes lean on me and the gauge dances around from max to min, but when Im on it hard, it recovers and stabilizes out to the rich zone. Idles healthy and timing is set. Still nothing for carb adjustments, just the two Idle mixture screws, thats all this carb has I guess. Now, its just the off idle and low load zones that makes it peg out lean. Stubbornly it just likes to drift off into the lean zone. You let off the throttle some and it instantly recovers to rich, then drifts away again. If didnt have an air/fuel gauge, I probably wouldnt even think there was a problem. That damn gauge just wont stay still in a good place.
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Old 11-01-2012, 02:39 PM
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Oh and another thing, I checked the accelerator pump, squirts nicely and begins to pump right off idle. The strangest symptom is the change between gas tanks. Riding down the highway, on the left tank the air/fuel is almost stable in the ideal range, (if you play the gas pedal just right.) Switch to the right tank and in seconds it will drift off to max lean, engine feels the same though. switch back to the left tank and it recovers to the ideal range quickly. What the hell.
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