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  Setting Idle Speed

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Author Topic:   Setting Idle Speed
MDF99
Gearhead

Posts: 232
From: Hamilton, Ohio, USA
Registered: May 2001

posted 05-17-2002 03:11 PM     Click Here to See the Profile for MDF99   Click Here to Email MDF99     Edit/Delete Message   Reply w/Quote
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

posted 05-21-2002 06:52 PM     Click Here to See the Profile for steve'66   Click Here to Email steve'66     Edit/Delete Message   Reply w/Quote
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

posted 05-21-2002 07:00 PM     Click Here to See the Profile for mustangboy     Edit/Delete Message   Reply w/Quote
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

posted 05-21-2002 08:56 PM     Click Here to See the Profile for steve'66   Click Here to Email steve'66     Edit/Delete Message   Reply w/Quote
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

posted 05-22-2002 01:13 AM     Click Here to See the Profile for Fastymz   Click Here to Email Fastymz     Edit/Delete Message   Reply w/Quote
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

posted 05-22-2002 01:18 AM     Click Here to See the Profile for Fastymz   Click Here to Email Fastymz     Edit/Delete Message   Reply w/Quote
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

posted 05-22-2002 11:12 AM     Click Here to See the Profile for uglydog56   Click Here to Email uglydog56     Edit/Delete Message   Reply w/Quote
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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