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Old 08-18-2004, 08:09 AM   #1
1986Silverado
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Tuning questions?

I am trying to get my truck running in tip top shape with what I have and have some questions......
1)What is the factory spec for idle speed? I just read 800 rpm in park...is that right? Seems high to me as I have mine set around 650 rpm in park, and that may be part of my problem
2)What is the factory spec for timing? Autozone states 4* BTDC...that seems a little low to me
3)How do I tune an edelbrock 1405 carb?
I tried tuning the carb yesterday with a vacuum guage following some instructions on a web page that somebody had linked in a thread on here, and I seem to make it worse. Gas smell is more noticeable now. Also when I cranked it this morning I had to keep my foot on the gas pedal to keep it from going dead, never had to do that before I fooled with the carb! Another
thing I noticed is after I got thru "adjusting" the carb, when I pulled the hose off of the pcv port on the carb it went dead......is it suppose to do that?
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Old 08-18-2004, 11:17 AM   #2
Russell
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hahaha, this sounds alllllll too familiar :p

I've got mine idling about 650 rpm in park, and 550 rpm in drive, its a bit too low, I'm gonna boost it up to about 600 - 650 rpm in drive. Most people set their timing to about 10 - 12 degrees, but yeah, the factory setting was about 4 degrees, my aircleaner says the exact same thing. I have absolutely no clue about tuning the carb itself though, mine still isn't working properly since I played with it, and I messed it up bad enough to be doing the EFI swap :p
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Old 08-18-2004, 06:43 PM   #3
flip66
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set ideal at about 700 to 650 in park. turn the mix screws all the way in to the right and then back out to the left about 2.5 turns then use the gauge. When you see max vacuum, vacuum stop going up, turn it back to the right just a little. Turn them in half turns do one side then the other that way you will keep them even.

Last edited by flip66; 08-18-2004 at 06:47 PM.
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Old 08-19-2004, 04:06 PM   #4
1986Silverado
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found a site edelbrock has on tuning these carbs and they say use the rpm method. Idle the truck up yo say 1000 rpms, turn one mixture screw to get the highest rpms, then back it down to get a 20 rpm drop, then do the other screw then reset the idle speed. I think I will try that this weekend unless some one can give me another manifold vacuum source besides the pcv port?! I don't think my hose was sealing thus the reason it is off now.
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