Carb problem - Team Camaro Tech
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post #1 of 12 (permalink) Old Sep 5th, 08, 06:09 PM Thread Starter
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Carb problem

i have a 750 holley double pumper with 4 corner idle and im having alot of trouble getting this thing to idle correctly.my idle mixture screws are not working properly in fact when you turn them all the way in its not killing the motor,its actually making the rpm go up.my cam has a 106 lobe sep.its idling rich.


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post #2 of 12 (permalink) Old Sep 5th, 08, 06:55 PM
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Re: Carb problem

check for vacum leak and float setting
crap in the needle and seat of the bowls
blown power valve .
time to check there first


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post #3 of 12 (permalink) Old Sep 5th, 08, 07:09 PM
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Re: Carb problem

I agree, either vacuum leak or float adjustment!
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post #4 of 12 (permalink) Old Sep 5th, 08, 07:21 PM Thread Starter
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Re: Carb problem

i checked for vacumn leaks could not find any,power valve is brand new


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post #5 of 12 (permalink) Old Sep 5th, 08, 07:28 PM
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Re: Carb problem

Quote:
Originally Posted by Bad67355 View Post
i checked for vacumn leaks could not find any,power valve is brand new
Next pull out the needles and clean them. Remember to count the threads that are exposed. Replace them, and then recheck your float levels.

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post #6 of 12 (permalink) Old Sep 5th, 08, 07:32 PM
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Re: Carb problem

Quote:
Originally Posted by Bad67355 View Post
i checked for vacumn leaks could not find any,power valve is brand new
just because its new doesnt mean its good!
ask me about my brand new MSD digital E curve distributor!
also if you have power brakes block off the vacum tube that goes to the brake booster diaphram.
there might be a hidden leak there.
also try this with engine running put your hand over the carb intake to block it off.
motor should die or almost die (no air getting in)
if it still runs you got a vacum leak


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post #7 of 12 (permalink) Old Sep 5th, 08, 07:47 PM Thread Starter
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Re: Carb problem

power valve is good i tested it working fine ,i dont have power brakes,i put my hand over the carb while it was running and it killed the motor


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post #8 of 12 (permalink) Old Sep 5th, 08, 08:04 PM
 
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Re: Carb problem

Make sure primary and secondary blades are set right-I set my idle with both to help get even idle screws.I close the blades all the way then crack the front back evenly-If you just idleing on one set it throws the whole thing out of whack on a 4 corner carb
At idle push down on one of the acc pumps-if it stumbles you are close or rich-if it speeds up its lean .
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post #9 of 12 (permalink) Old Sep 6th, 08, 08:40 AM Thread Starter
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Re: Carb problem

i have the blades set with less than .040 of the transfer slot showing like holley reccomends


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post #10 of 12 (permalink) Old Sep 6th, 08, 06:50 PM
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Re: Carb problem

Mike..have you got your ignition dialed in first?The carb is a passive device and responds accordingly.
sure sounds like your a/f ratio is pig rich at idle.if the ignition timing is close to known combos..then move to the carb.
If your idle mixture screws seated increase rpm..you are sourcing fuel elsewhere.Could be a mispositioned pv gasket..shrunken gasket..warped body or block etc etc.perhaps your valve timing events call for more rpm at low speed and requires the secondary blades to be cracked a tad and allow you to back down the primary throttle angle..or an old school bandaid ,drill the plates for additional air at idle with a lumpy cam at idle speed.

George
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Last edited by fatblock; Sep 6th, 08 at 06:58 PM. Reason: spelling
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post #11 of 12 (permalink) Old Sep 7th, 08, 08:35 PM Thread Starter
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Re: Carb problem

my initial timing is 17 and my total advanced timing is 38 degrees.i have my throttle blades set as there is not much of the transfer slot showing,i have 5/64" h0les drilled in the primary blades now.


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post #12 of 12 (permalink) Old Jan 25th, 09, 02:14 PM
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Re: Carb problem

Where are the idle screws set to obtain the best idle? If they are less than 1 turn out, you need to restrict the idle feed circuit in the metering blocks. I would also give it more timing.

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