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greythorn3 08-17-2006 06:54 PM

Rochester Quadrajet! help
 
I am in the process of rebuilding my rochester quadrajet carb m4me or such... anyhow i took out my power piston stop and spring, and have no idea of the general ammount of turns it should be out.. anyone ever do this? or know a good setting that is emissions friendly? ive been searching the internet for over a hour and cannot find a base setting.. so im here for all the carb guru's help.. thanks in advance


RAy :welcome:

ChevelleSS_LS6 08-17-2006 07:44 PM

I wish my uncle, or grandpa were around right now... they can tune any hesitation, any problem, out of a qjet. :cool:

Unfortunatley, I was raised in the fuel injection for the masses age, so this is unknown country for me. From experience and most service manuals, for tuning screws and otherwise it's 1.5 turns back of the seat/bottom. Hope my efforts help!

dgcantrellsr 08-17-2006 08:08 PM

Quote:

Originally Posted by greythorn3
I am in the process of rebuilding my rochester quadrajet carb m4me or such... anyhow i took out my power piston stop and spring, and have no idea of the general ammount of turns it should be out.. anyone ever do this? or know a good setting that is emissions friendly? ive been searching the internet for over a hour and cannot find a base setting.. so im here for all the carb guru's help.. thanks in advance


RAy :welcome:

It's been a few moons ago but I used to drive the little plug out of the top part that lets you get access to the stop screw and I think I used a double D type screw driver or something to tweak it after I got it running. But I don't remember the start setting.

olescarb 08-17-2006 08:24 PM

the power piston stop or APT screw is set at the factory to give the engine the correct cruise a/f mixture. a good place to start is 3 1/2 turns from the bottom, then use it to adjust the cruise mixture. the way we set the cruise mixture is with a exhaust gas analyzer, the CO reading taken in front of any catalitic convertor and with any smog pump disabled is to target a CO reading of 0.75 -1.25% CO. (any smog shop should be able to give you the readings for just a few$),you could also use a air/fuel meter such as the Innovate Motorsports LM-1 and then target a air/fuel mixture reading in the 14.2-14.5 to 1 range. i know of no easy way to do the APT screw other than those methods or trial and error spark plug readings.

henry @ oles carb

jimfulco 08-18-2006 01:45 AM

http://buickpartsdirectory.com/QJet_Tuning_Paper.doc

There's some info on power piston adjustment at the bottom of this document.


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