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Discussion Starter #1
Can someone give me some advice on this carb. It's always run rich at idle or that's where I notice it by the gas smell and my plugs and exhaust pipes are black. I just rebuilt the carb last week because it was gunked up from sitting around for almost a year without running and I wanted to eliminate that as a possible cause for it not running right. I got it running this past weekend and it seems to be running good but I haven't taken it out on the road yet. I've been reading on how to set it back up after taking it apart and in particular the transition slots, before rebuild the secondary slots were open too far and I figured that contributed to it being rich. I had set the rear transition slot to a little square which is what I read it needed to be and when I put the carb on I could not get it to idle down past about 1100 rpm. Then reading other posts and watching videos I read that the secondary slot should be closed off, so I adjusted it to be closed and now I can turn the idle down, but I'm still having the rich smell issue and the idle mixture screws give me the highest rpms with them at about 1 turn out. The carb new had 70 air bleeds for the high speed and 3 x 28's and one 25 for the low speed (hopefully that's not backwards but you get the point). Weird that one was a 25 from the factory but I put everything back to 70 and 28 but still runs like it did a year ago before I had to rebuild the engine (383). Vacuum yesterday was at about 15 inches, and the curb idle is set at about 18 deg. with the rpm's at about 750-800.

Before the car seemed to run great when driving and I didn't have any stumbles or hesitation issues, the only issue was it running rich at idle since I've had this carburetor for over two years. I'd really like to finally get this carb dialed in like it's supposed to be especially since I just got the engine rebuilt.

My question is should the transition slots on the secondary be closed or open like a little square or should I increase the idle air bleeds to get the idle cleaner? Maybe hotter spark plugs (Ive got a set of NGK FR5 plugs that I bought but not installed yet) and I'm not sure how hot those are. Right now I have Autolite #3923 installed which came with the engine.

Thanks in advance for any help or advice.
 

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The throttle should be closed far enough at idle that the transition slots are not exposed to vacuum. Also, you should be able to turn the idle screws in and stall the motor.
 

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Holley throttle blade adjustments.
*Primary Throttle Blades - Looking from underneath carb, you should see a "square" portion of the idle transfer slot below the throttle blades when adjusted correctly.
*Secondary Throttle Blades - First: Completely close them until the blades just touch the throttle bores. > Once the secondary throttle blades are just touching the bores, turn the secondary throttle adjustment screw about an 1/8 of a turn to open the secondaries. This adjustment keeps the secondaries from binding in the throttle bores.
 

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RifRaf is right. I guess it's been awhile. The important thing is that you can turn the idle screws in and the idle speed drops. If you screw them all the way in and the engine is still running, your throttle blades are likely open too far.
 

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Discussion Starter #5
Thanks guys. I took it back off and readjusted the secondary blades and I am now able to adjust my throttle. Still a little rich at idle though and I've ordered some idle air bleeds to try. I've got 70's now and I ordered 72 and 74's to see I can finally get the idle cleaned up.
 

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Is that a 4 corner idle carb? If so I bet you have an extra curb idle hole right under the transfer slot along with an idle hole to the side of the transfer slot. The one under the transfer slot is not needed with the 4 corner idle. So your getting more fuel than needed. Check out racingfuelsystems.com great info on the carb your working on, and fixes for the rich idle. I hope this will help you out.
Mark
 

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Discussion Starter #7
Hey thanks for responding. I just noticed I had a response. I went to racingfulessystems.com but I don't see any forums or posts. It almost seems like they just built the site. Anyway, I've got it running a little better by leaning out the idle air jets. It's still not perfect but much better judging by my plugs. Tan in the middle but still black on the threaded portion. Much improved though.
 

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Sorry about that address. It's taptalk.com/groups/racingfuelsystems/ I'm sure you will find just what you need.
 
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