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Author
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Topic: Setting Idle Speed
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MDF99
Gearhead Posts: 232
From: Hamilton, Ohio, USA
Registered: May 2001
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posted 05-17-2002 03:11 PM
   
I need to set the idle speed on my rebuilt and freshly broken-in '66 289. It has a manual tranny and a solid lift cam that's a little choppy (236/242, .536/.544), 10.5:1 compression and a 650 double pumper carb. Is there a science to setting idle speed or do you just go by feel and increase the revs till the motor seems happy? Right now it starts running pretty rough around down around 1000 rpms. What's a ballpark idle speed for this engine? I'm thinking around 1200 or 1300? Thanks.[This message has been edited by MDF99 (edited 05-17-2002).]
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steve'66
Gearhead Posts: 8796
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 05-21-2002 06:52 PM
Matt,Your engine should idle well around 800. Get a vac. gauge and adjust your idle screws for max vacuum, then lower your idle speed and do it again. Also recheck your initial advance, you'll want a quick mechanical advance that is limited. Like 12-34 degrees btdc. 12-14 at idle and 34-36 total around 3000 rpm. If it still won't idle well get out a can of spray carb cleaner and check for intake leaks, or try to smother the carb with your hand, it should die and if it doesn't you've got a vac leak. Good luck, SteveW
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mustangboy
Gearhead Posts: 774
From: Ont, Canada
Registered: Mar 2002
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posted 05-21-2002 07:00 PM
I've got a 244 dur .518L cam in my 302 and it idles at about 1000-1100 at about 12-14 inches of vacuum.While it will idle a little slower it stalls often when taking off and is harder to start at the lower idle.The engine seems "happy" as you said at the higher idle speed.
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steve'66
Gearhead Posts: 8796
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 05-21-2002 08:56 PM
MB,You should do what Matt's gonna do too. It'll idle better than that.  SteveW
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Fastymz
Moderator Posts: 18590
From: Reno Nv USA MEM#1240
Registered: Apr 2001
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posted 05-22-2002 01:13 AM
Is that ture for auto's and sticks too.My car idles best in park at 1100-1200 and then drops down to 750 in drive.Should I get it down lower?SCOOP ------------------
65 coupe,351w,C4,Big Boss 429 hood scoop,Crager SS,Black Suede. It maybe slow,but it's not fast either.:) https://mustangsandmore.com/ubb/Fastymz.html
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Fastymz
Moderator Posts: 18590
From: Reno Nv USA MEM#1240
Registered: Apr 2001
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posted 05-22-2002 01:18 AM
Ok I have a dumb question,were do I hook the vac, gauge to?
Do I use a port on the carb,the manifold port I have is for the trans and it's a brass screw in.SCOOP ------------------
65 coupe,351w,C4,Big Boss 429 hood scoop,Crager SS,Black Suede. It maybe slow,but it's not fast either.:) https://mustangsandmore.com/ubb/Fastymz.html
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uglydog56
Journeyman Posts: 6
From:
Registered: May 2002
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posted 05-22-2002 11:12 AM
manifold vacuum source. Vacuum method works the best. Compared to my ear tune, my car runs smoother, and has 5" more vacuum at idle, and the plugs look better, too. I have a "lean" ear. 
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