Classic Mustangs (Tech) Technical discussions about the Mustangs of yester-year.

Flat spot from idle

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Old 04-14-2007, 10:53 PM
  #1  
rhinobacker
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Default Flat spot from idle

Help me, I've adjusted the timing but still have a flat spot on my 68 289 from idle to about 3500rpm then it's fine.
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Old 04-14-2007, 10:59 PM
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350kmileFord
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Default RE: Flat spot from idle

Sounds like my Mustang, 'cept it only lasts till about 1500 rpm.
Same issue on my '71 F-250 >_<

It goes away completely on the Mustang once it's warm though.
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Old 04-14-2007, 11:18 PM
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rhinobacker
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Default RE: Flat spot from idle

Strangely enough after I had her running for little while yesterday it did get a bit better. Given that she is unregistered at the moment I can't rlegally take her for a big drive but I will try and leave her running for while and see what happens. Thanks.
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Old 04-15-2007, 02:53 AM
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alderpulp
 
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Default RE: Flat spot from idle

my 68 289 was the same...a friend rebuilt the 2 barrel carb for me....it got better, but didn't go away...I just put in a petronix pointless ignition, and it has GREATLY improved the flat spot......it is very very minor at this point...ap
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Old 04-15-2007, 05:12 AM
  #5  
rhinobacker
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Default RE: Flat spot from idle

Thought I better add a photo of my girl. She is in need of some TLC, but that was one of the reasons I bought her.

[IMG]local://upfiles/66019/1E3D056E4B0941A2821DD1C4CB3816BE.jpg[/IMG]
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Old 04-15-2007, 05:52 AM
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350kmileFord
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Default RE: Flat spot from idle

A fellow deuce-panner >_<
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Old 04-18-2007, 07:30 AM
  #7  
rhinobacker
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Default RE: Flat spot from idle

The flat spot has now moved to 1500rpms. I've put in a new coil and went to gap the points and adjust the dwell and the f0rken points and condenser looked 40 years old. I feel like an idiot. Why would someone change distributor cap, rotor, leads and plugs but not the points (the previous owner). I should have looked at these first. Hopefully this fixes everything. BTW I am working on a Dwell of 30 degrees. Does anyone disagree?
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Old 04-18-2007, 12:59 PM
  #8  
Soaring
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Default RE: Flat spot from idle

According to my Haynes manual, the '68 289 dwell angle is 27. Point gap is 0.021 and the initial timing is 6 degrees BTDC.
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