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Discussion Starter #1 (Edited)
I'll start with some information on my combo. I searched but didn't see exactly what I was looking for, so hopefully some of you guys can help me out.

Mopar 360
9:1
216/224, .506/.506, 114
Airgap intake
18* timing @ idle, 33* all in by 2500
13.5" Hg @ idle

Quick Fuel 650 dp (hr-650)
Primary jet 72
Secondary Jet 76
Idle Air Bleed 70
HS Air Bleed 28
Primary Nozzle .037
Secondary Nozzle .037
Needle and Seat 100
Primary Power Valve 6.5
Secondary Power Valve delete

If this is not enough info just let me know.




The problem I'm having is that the transition circuit is running super lean. If I set the idle to maximum vacuum (~14.5 afr), the transition circuit(up to ~2k rpm) will be super lean (16-17+ afr) at light cruise speeds. Above 2k, when the primaries kick in, it'll run fine.

At first I thought the primary jetting was too lean so I jetted it up, all the way up to 78 with no change whatsoever in the range below 2k rpm. The only change would be above 2k rpm when the primaries take over and would be very rich.

I'm not sure if it's a big deal, but one thing that raised a flag for me was that I need to turn the idle screws in a lot to get the idle afr correct. To get maximum vacuum at idle the screws need to be turned to less than 1/2 turn out (4 corner idle). Everything I've read says that somewhere between 1-1.5 turns out is normal so I don't know why mine needs to be turned in so far.




Any idea of what this could be? I thought it may be an idle air bleed problem so I pulled the air bleeds to see what would happen and all it did was move the afr from 10.5 to 14.0, but again the transition circuit would be super lean. I haven't even started to tune the rest of the carb because I want to get this sorted out first. I'd appreciate any help you guys can give me on this problem.

Thanks
 

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pig hunter
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go up on the idle air bleed to lean out the idle curcuit, to you get the idle screws to 1 1/2 turns out.
 

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pig hunter
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sorry forgot go down on the int bleeds to richen the cruise.. btw primery jets are for wide open throttle only.
 

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pig hunter
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you have 2 or 3 air bleeds on the top of the carb?
 

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pig hunter
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go up on the idle bleed to lean the idle out and the int should be in the metering plates.. primary nozzles go up those are jets for the int curuit
 

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Post the length and width of the transition slot.

Another thing to help the smarterers, it might be worth finding the point in the transition where its actually giving you trouble ,ie: blade position relative to slot, so the smart guys have more to work with.
 

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I wouldn't worry about the lean numbers on your AF gauge, as long as you have no surging or tip in stumble from the transition circuit. When running at light load conditions like a steady state cruise on the transition circuit it's not abnormal to see numbers above stoich, the loads are low and fuel needs are low as a result. Use your AF gauge to look more at the fuel curve at WOT from lower to peak RPM. Read your plugs!
 

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Discussion Starter #11
The transition slot isn't quite square, but it is pretty close.

I just recently installed an a/f gauge so I have numbers to show what I've been feeling (surging at light cruise) for a while now. In the past I just richened up the idle a bit and went about my business living with a stinky rich idle. Now that I have the ability to see more of what's going on I'd like to get it a little closer. Getting better mileage wouldn't hurt either.

After doing a little more research I think I'm going to try upping the idle feed restrictor a bit. Maybe a little tweaking on the idle feed restrictor and idle air bleeds will get it where I want.
 

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It sounds to me like you need to drill a small hole in the butterflies and the lose the throttle more. If it is surging with the idle srews closed that far it sound like you are running out of transition slot to me. If that doesnt work then i would put a smaller bleed in it.
 

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Go down on the idle air bleed first, try around a .067. If you get to .060 and still not enough then go to a smaller idle jet.
 

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Not saying that this is your problem,but every QF carb I have used I have had to go down on the idle feed restrictor in the metering plate.
Does your distributor have a vacuum advance on it ?
 

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Discussion Starter #17
I've made an order for both idle restrictions and air bleeds so I can mess with it this weekend. I'm thinking I need a larger idle restriction to richen the transition up a bit, but I've got several sizes bigger and smaller to experiment with. I guess we'll see.

I don't run a vacuum advance on my distributor.
 

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I think Mark got his mords wixed, I’m sure he meant to say, “larger idle jet.” He had open-heart surgery a couple weeks ago so cut him some slack. :)
 
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