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Author
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Topic: Holley DP question
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kid vishus
Gearhead Posts: 6220
From: middle of NC
Registered: Oct 2000
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posted 08-16-2003 02:39 PM
   
It was mentioned some time back that I needed to open the secondary blades a little to get it to idle better (on my 750 annular discharge carb). How much is "a little"? Is there a certain measurement with a feeler guage I should shoot for? Or is an entirely by site/trial and error?
I attempted to open them up a little, but like an amateur, I went the wrong way with the screw the first time, so I have no idea where it should be to even be in the original spot. (so saying 'two turns from stock' wont do me any good now.)Thanks
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John Holloway
Gearhead Posts: 859
From: Romeoville Illinois
Registered: Jul 2000
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posted 08-16-2003 04:11 PM
Kid,Turn the carb over and look at the secondary bore, you will see the transfer slot when you open the throttle plates,when the throttle plates are closed you should not see the transfer slot...so back off the screw on the secondary plates are shut then turn the screw till the transfer slot looks like a pin hole the size of a needle.
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kid vishus
Gearhead Posts: 6220
From: middle of NC
Registered: Oct 2000
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posted 08-16-2003 04:17 PM
Thanks.  I've never had to mess with anything like this before so it's all new to me.
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powrshftr
Journeyman Posts: 77
From: Sarnia,Ontario,Canada
Registered: Apr 2003
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posted 08-16-2003 10:40 PM
Kid,if you end up adjusting 'til the throttle blades are past the slots without getting any positive results,try pulling the throttle blades,and drilling a small hole (about 1/16") through them.Some guys end up doing this on engines with LOTS of cam, that don't like to idle;it seems to help.
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bluestreek
Gearhead Posts: 1724
From: Athens,GA
Registered: Jul 2001
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posted 08-16-2003 11:04 PM
I have had success drilling a small hole in the rear vacuum plug starting with 1/16". Then readjusting the idle mixtures afterwards. It's a simple little experiment that doesn't involve removing the carb.
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Strain Gang
Gearhead Posts: 220
From: Thor, Iowa
Registered: Mar 2003
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posted 08-17-2003 01:15 PM
Kid, I have been fighting the same problem, only my sec. screw fell all the way out. Installed a new one according to Holleys book at 1 turn open from when it touches. Then I readjusted the 4 corner mixture screws. Not saying it will work for you, but it did for our car. Good luck, Steve.
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Helping Hands
Journeyman Posts: 41
From: Salem,OR
Registered: Jul 2003
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posted 08-17-2003 10:13 PM
I have always strived to adjust the primary and secondary throttle plates to be open an equal amoumt.That way not much of the transfer slot is being used.It takes a few times with the off again on again, but worth it. Work's for me.
[This message has been edited by Helping Hands (edited 08-17-2003).]
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jsracingbbf
Gearhead Posts: 2805
From: Batesville,MS. , U.S.A.
Registered: Mar 2002
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posted 08-17-2003 10:39 PM
Seems like I saw a post somewhwere where someone made a way to adjust the secondary blades from the top, that would be slick! I coulda used that trick back a year or two ago. Sorry KV I don't remember the details. maybe it's a bought kit? JS
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Helping Hands
Journeyman Posts: 41
From: Salem,OR
Registered: Jul 2003
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posted 08-18-2003 02:10 AM
You can unscrew the secondary idle speed bolt from the throttle body and install it from the top.It takes a thick, narrow screw driver as the threads are small and will get damaged easily.I have seen in Jeg's that you can also get a bracket that will bolt to the secondary throttle shaft that will allow you to adjust the secondary idle speed from the top.Holley makes one and I think Quick Fuel also makes one for about $10 cheaper. [This message has been edited by Helping Hands (edited 08-18-2003).]
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