| Rodchester quad mixture adjustment [message #364134] |
Thu, 20 May 2021 09:22  |
tgeiger
Messages: 518
Registered: February 2006
Location: kansas city
Karma: -1
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Senior Member |
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Quick question, what is the full turn count on the fuel mixture screws on the Rochester quad from the seated position? Trying to get a good starting point to do a maximum vacuum air/fuel mixture setting. I’ve watch videos and the back out number seems to vary a bit. And also, what port on the carb should I take a vacuum reading from? The video says PCV valve but mine looks like that port goes to the distributor’s vacuum advance can.
Thanks,
TG
Tom Geiger
76 Eleganza II
KCMO
[Updated on: Thu, 20 May 2021 09:29] Report message to a moderator |
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| Re: Rodchester quad mixture adjustment [message #364135 is a reply to message #364134] |
Thu, 20 May 2021 09:54  |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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I do it the way GM books say. Engine at 195, air cleaner and preheat on if you have the long adjustment tool is best. If not you will have to do without aircleaner. Go for max rpm at the lean point where it just starts to drop but does not. You have to alternate back and forth to get both sides balanced. So just at the point where RPM would drop if you turn either any more clockwise. Then if you want to be emissions compliant, turn one screw in til 25 RPM drop is seen, then turn other screw in until you see an additional 25 RPM drop. This give a 50 RPM total lean drop idle. (You could also do like 15 a side and be a bit smoother in my opinion). Finally reset your base idle screw as needed. As far as how many turns, the screws only trim fuel in the first couple turns out from closed range, and opening them further will not add fuel by design on most Qjets I have adjusted.
I don’t like the max vacuum method as that would typically be richer/dirtier.
John Lebetski
Woodstock, IL
77 Eleganza II
[Updated on: Thu, 20 May 2021 09:55] Report message to a moderator |
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