General Category > Quadrajet Carb Talk and Tips

idling issues

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Cliff Ruggles:
Too large for idle tubes, .039-.040" should have been enough.

Idle airbleeds should have been around .070" for that carb number, not closer to .080".

What in the idle system is drilled to .203"?  Idle bypass air?

What are the idle down channel restrictions drilled to?

Holes in the throttle plates?  Why?......Cliff

j_oetjens:
thanks for the reply

I have your book and followed example #3 on every thing except the idle tubes as I was unable to remove them. Then I followed what it said in the book about starting small and then working in small sizes and going up. While testing and trying things everytime I put the carb back on and it would not run properly I increased all the holes up a size until finally I got it to at least idle and stay on at least in park.

Too large for idle tubes, .039-.040" should have been enough.
When I was able to remove them I did them to 0.039 and still no changes. Then to 0.0394 and still no change. Then the next size I had was 0.0472 and drips from boosters almost completely stopped. But did not increase anything else just idle tubes.
Idle airbleeds should have been around .070" for that carb number, not closer to .080".
As mentioned above increased sizes together everytime I removed carb.

What in the idle system is drilled to .203"? Idle bypass air?
yes idle bypass air in baseplate is 0.203 this is the only hole I did by its self to increase air flow. I increased from 0.1875 to 0197 and still would not idle properly so I drilled out primary butterflies and it got better then I increased from 0.197 to 0.203 it finally stayed running better

What are the idle down channel restrictions drilled to?
down channel: 0.0625

Holes in the throttle plates? Why?......Cliff
as in your examples it says optional so when I got to a certain point with the idle bypass air I drilled them out to see if it would help. I understand that holley and quadrajet are 2 different systems but I drilled out all 4 butterflies in my holley and it made a day and night difference when I was tuning my holley. So that played a part in me drilling out butterflies when it still would not idle properly as your book says as an option. I do have a spare carb that I can change them if you think it would help.

Cliff Ruggles:
Increasing idle airbleed size KILLS pull to the idle screws even with larger settings.  If anything, make them smaller, not larger.

.203" idle bypass air is nothing but a HUGE vacuum leak.  If you don't have enough fuel to the mixture screws, idle bypass air will NOT help to control nozzle drip.

If the carburetor is a later model, and has idle bypass air, there is no need to drill the throttle plates, as idle bypass air is much more effective.

If you can't get on the idle system with .110" bypass air and that engine/cam combo, something else is wrong someplace.

That's not really that big of a cam in a 455 engine, only 284 degrees seat to seat timing.

We've ran 308-320 degree cams in 455's with zero issues for idle fuel delivery using smaller settings that what you are using.

I'd go back to the idle airbleeds and make them smaller, and things will start to work better everywhere else......Cliff

j_oetjens:
I will try that thanks for your response it is greatly appreciated  I will work on it this weekend and get back with you

j_oetjens:


 idle great news everything is running perfect I think I decreased idle air bleeds to 0.070 and got a rebuild kit and with  timing at 10 degrees. its idling great at 800 no nozzle drip, idle mixture screws respond great starts great hot or cold, and just a tap of the gas pedal will give you whip lash. I didn't decrease idle bypass air in base plate due to gasket has hole 0.125 so I did not drill out new gasket.

 thanks everyone that posted especially you cliff  ;

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