12-26-2002, 12:47 PM
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CC Member
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Join Date: Jul 2001
Location: Southwest,
WI
Cobra Make, Engine: Shell Valley, Mopar thingy (small block of course)
Posts: 2,215
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Not Ranked
Carb vacuum/idle
I was checking the vacuum on the 4160 to try to get the highest vacuum reading while adjusting the idle mixture. Turning the idle mixture didn't really change anything, but when I pulled the plug on the vacuum port to put the vacuum guage on, the idle went up 200 - 300 rpm.
I get about 9.75 inches at 1100 rpm idle, which makes me think there may be a vacuum leak.
Cam is 292 duration on both lobes and 106 degree centerline.
The idle is fine, doesn't get hot, but it does seem to load up a bit. I am happy enough with it, and this may be the best it gets with this cam.
I mostly want to know why the idle would go up when the vacuum port is open?
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Brent Dolphin
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