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Old 08-22-2016, 10:17 PM
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Texasdoc Texasdoc is offline
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Join Date: Feb 2012
Location: Keller, TX
Cobra Make, Engine: Lonestar Classics LS427. Self-built 408W, AFR 195 heads, Performer RPM Intake, Quick Fuel 750, 407rwhp, 479rwtq
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Anyone have any suggestions on what changes to make? I have the original jets that came with it - 74 primary, 82 secondary (with extension tubes). 6.5 PV. I have the idle screws set where it idles about 13.5:1. I think it is very rich thru the transition circuit.

I've also noticed (and noted here before) that minimal changes in the idle screws make a huge difference in the AFR at idle. 1/16th of a turn of the idle screws will change the AFR by a whole point.

Primaries are set where the transfer slot is square (as tall as it is wide). I use the secondaries to set the idle speed (1000 rpm).

Frequently, the car seems like it doesn't want to return to idle. The RPMs will hang around 1200-1300 and eventually creep back down to 1000. I have two throttle return springs so I'm pretty sure it is returning to the stop screw.

Idle - 13.5
Off idle/cruise at 1500 rpm - 11.0
Light acceleration - 12.0-12.5
Medium acceleration - 13.0
WOT - starts rich 12.5, ends at 13.5

Letting off the throttle, it goes pure lean (gauge pegs at 17) then settles down to idle at 13.5. Going around a corner or heavy braking also goes lean. Fuel is 1/2 way up the sight windows on primaries and secondaries.

Thoughts?

Last edited by Texasdoc; 08-22-2016 at 10:49 PM..
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