79 Mustang over-fueling issue

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   So, I've been fighting an over-fueling issue on this thing for awhile.  1979 Mustang with the stock 302 and stock 4160 carb.  It's most noticeable at idle so I'm thinking "Well just adjust the idle adjustment needles.  I turn the needles in to try to get the engine to stumble and nothing, I have the needles in and completely seated and I'm still puffing out a little black smoke at idle but not as bad as what it was. 

I'm a little confused on what to do here because I've only had Weber carbs my whole life, never messed with Holley, and it doesn't seem like there are any jets beyond the primaries that I can change out.  So...  what the heck?

Thanks!

P.S.
Just finished rebuilding the carb, cleaning out everything from top to bottom, and setting the floats.  It did this before the carb rebuild, it runs a little better after but, still same fueling issue.

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KooK Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: February-10-2014 Location: Iowa Status: Offline Points: 143	Post Options Post Reply Quote KooK Report Post Thanks(0) Quote Reply Topic: 79 Mustang over-fueling issue Posted: April-01-2017 at 7:13pm
	So, I've been fighting an over-fueling issue on this thing for awhile. 1979 Mustang with the stock 302 and stock 4160 carb. It's most noticeable at idle so I'm thinking "Well just adjust the idle adjustment needles. I turn the needles in to try to get the engine to stumble and nothing, I have the needles in and completely seated and I'm still puffing out a little black smoke at idle but not as bad as what it was. I'm a little confused on what to do here because I've only had Weber carbs my whole life, never messed with Holley, and it doesn't seem like there are any jets beyond the primaries that I can change out. So... what the heck? Thanks! P.S. Just finished rebuilding the carb, cleaning out everything from top to bottom, and setting the floats. It did this before the carb rebuild, it runs a little better after but, still same fueling issue.

Gary S Members Profile Send Private Message Find Members Posts Add to Buddy List Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096	Post Options Post Reply Quote Gary S Report Post Thanks(0) Quote Reply Posted: April-01-2017 at 7:42pm
	Ever check or change the power valve?
	69 Mustang HM SS 95 Nautique Super Sport

KooK Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: February-10-2014 Location: Iowa Status: Offline Points: 143	Post Options Post Reply Quote KooK Report Post Thanks(0) Quote Reply Posted: April-01-2017 at 9:13pm
	There were two power valves in the Holley rebuild kit, either a 2.5 (I believe 2.5) or a 6.5, and I went ahead and threw a new 6.5 in.

SNobsessed Members Profile Send Private Message Find Members Posts Add to Buddy List Grand Poobah Joined: October-21-2007 Location: IA Status: Offline Points: 7102	Post Options Post Reply Quote SNobsessed Report Post Thanks(0) Quote Reply Posted: April-01-2017 at 9:17pm
	Not an expert, but I have read that if idle adjustment is not responding, one possible cause can be that the idle stop screw (for throttle plate) is turned in enough that the 'transition slots' are exposed If so, then the carb isn't running off the idle circuit.
	“Beer is proof that God loves us and wants us to be happy.” Ben Franklin

KooK Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: February-10-2014 Location: Iowa Status: Offline Points: 143	Post Options Post Reply Quote KooK Report Post Thanks(0) Quote Reply Posted: April-01-2017 at 9:25pm
	Mmmmmmmmmm, I can try to mess with that tomorrow, but I have the idle set at ~825rpm.

KooK Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: February-10-2014 Location: Iowa Status: Offline Points: 143	Post Options Post Reply Quote KooK Report Post Thanks(0) Quote Reply Posted: April-10-2017 at 9:11pm
	An update on this. I put a fuel pressure gauge on because I didn't want to mess with the carb without knowing it's worth messing with. Fuel pressure shows around 5 - 5.5psi so that looks fine. Went back to the carb and did what SNobsessed said. I closed the throttle plates and idle and reopened them with the idle mixture screws set to initial at 1.5 turns out. Got the engine to idle at 825 again and instead of listening for the engine to stumble, I noticed that I can see fuel start to come from the primaries if the idle screws are in too far. So I increased them both 1/4 turn in until fuel started coming from the primaries and turned them back off 1/2 turn. Seems to be doing pretty well now! Now I gotta start looking at engine rebuild parts because the cylinders are as smooth as a babies bottom and I have terrible leak down numbers with compression loss past the rings.

79 Mustang over-fueling issue

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