Holly carb tuning question... - Team Camaro Tech
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post #1 of 3 (permalink) Old Aug 20th, 03, 12:50 PM Thread Starter
 
Join Date: Jul 2003
Location: Rock Island, IL USA
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Hi everybody, I need a little help with tuning a Holley carb. The basic specs: 600CFM, double pumper with mechanical secondaries. The choke plate and shaft have been removed. The problem: I obtain my best vacuum reading with both idle mixture screws all the way in (seated). I get a reading that fluctuates about 16 to 17 mmHg. This is with the idle stop screw backed off the stop as well, it idles around 750 to 800 RPM. I also hear what sounds like a vacuum leak, it sounds about the same with the air cleaner on or off the carb. I have tried spraying carb cleaner around the various mounting flanges, fittings and hoses etc. No real increase in idle is detected, could the sound that I think is a leak actually be the air rushing in the throttle bores?
Thanks.....
Scott

[ 08-21-2003, 04:30 PM: Message edited by: Scott Vinzant ]

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post #2 of 3 (permalink) Old Aug 22nd, 03, 11:22 AM
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Join Date: Feb 2003
Location: KC
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Scott,

It sounds like your secondaries are open too far. I don't remember the adjustment exactly but it seems like you back out the adjustment screw until the secondary is closed completely and then adjust in until the screw contacts. Once that occurs you turn it in 1/2 of a turn more. This should give you a good starting point. If you do some searches you'll find more posts on this here or on the chevelle site.

Ted
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post #3 of 3 (permalink) Old Aug 23rd, 03, 05:17 PM Thread Starter
 
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Ted, I though I made the secondary adjustment whenI rebuilt the carb, but just to make sure, I pulled it off and re-did it. I think it did close them down just a bit. I need to get it out on the road and see how it runs, I may need to do a bit more tweaking though....
Thanks again...
Scott

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