Author Topic: Idle Speed, What's the deal?  (Read 2696 times)

Offline 85MudMonster

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Idle Speed, What's the deal?
« on: January 13, 2008, 12:51:22 am »
Me again with more questions. Okay, My truck used to idle at about 1200rpm (i'm guessing, no tach, and no timing bracket down on the balancer to use the light) I took the truck all the way home (Springfield Mo. from Shreveport it's like 422miles, actually got 13.5 MPG there and 11.5 MPG back, but I was hauling about 700lbs of stuff my parents gave to me) Anyway, while there my Dad mentioned the idle seemed way too high. So we adjusted the idle speed screw on the Quadrajet, and it smoothed out, but seemed a bit low when in gear. After I got back home I tried to hook up a dwell Tachometer unit to see what it's idle was, but it was broken, to I bought a nice little tach. Long story short, when in Park it idles right around 600-700rpm, which is like right about where it should be, but when in drive/reverse the idle drops down to about 400-500 and it sound like it's going to die although it doesn't. I know that the idle should drop a bit when in gear, but not 200rpm, right? Could this be a vacuum problem? That is what it seems like but maybe not, I do know that the truck has some vacuum line issues that will hopefully be fixed tomorrow. Anyway, any thoughts or comments?

Sorry I ramble on.....
Dan

85 Chevy K10 - 408 BBC from a 71 Chevelle SS, TH350, NP208, 33" Mastercraft Courser M/T

Offline VileZambonie

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Re: Idle Speed, What's the deal?
« Reply #1 on: January 13, 2008, 07:41:33 am »
#1 make sure you have no vacuum leaks. #2 you need to check your timing. Make sure your advance mechanism is working correctly and is set up correctly. You can buy a timing tab for about $3.00 from summit or just make one yourself with the piston at TDC#1 just make a pointer line up with the notch on your balancer. Your RPM will drop when you put it in gear. Where do you have your vacuum advance hooked up to? ported or manifold vacuum?
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Offline 85MudMonster

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Re: Idle Speed, What's the deal?
« Reply #2 on: January 13, 2008, 12:28:02 pm »
The advance is hooked up to one of the vacuum ports on the front of the carb. where should it be hooked to?
Dan

85 Chevy K10 - 408 BBC from a 71 Chevelle SS, TH350, NP208, 33" Mastercraft Courser M/T