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Hi folks, I believe I have either a 600 or 650 holley vacuum secondary on my 355 small block. I did mess with the idle air screws once too try and fix the problem but my problem is that the motor idles at about 800 rpm for a few seconds and then it will elevate to 1000rpm and back down again.. Back and forth. Idk if anyone know about adjusting the idle air screws and how to adjust the floats..Thanks
 

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Could be advance fluctuating in the distributor. One weak spring could cause that.
To adjust your float remove the site plug on the side and adjust the fuel level so the fuel just barely dribbles out.
To adjust the air bleeds set them both at 1 1/2 turns out. Hook up a vacuum gauge to a manifold source and adjust them to get the highest idle.
Do you have your vacuum advance hooked up. And to where?
 

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Hi folks, I believe I have either a 600 or 650 holley vacuum secondary on my 355 small block. I did mess with the idle air screws once too try and fix the problem but my problem is that the motor idles at about 800 rpm for a few seconds and then it will elevate to 1000rpm and back down again.. Back and forth. Idk if anyone know about adjusting the idle air screws and how to adjust the floats..Thanks
Before you blame the carb, set the timing curve up correctly if you haven't already done so. THEN see what the carb needs.;)

The carb number- usually found on the airhorn- will tell you what you have.
 
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