Posting for a buddy of mine, I know this isn't the B Body forum but hoping someone had the same issue. 67 Charger with the original factory installed 440 with automatic. Solid lifter cam nothing crazy Holley street dominator intake, 850 Holley carb, stock exhaust manifolds with 3:91 gears. The car runs strong but has developed a secondary stumble with the 850. Tried bigger jetting and gets worse. Put on a Edelbrock 650 AVS-2 great throttle response but still has secondary stumble. Put the 850 back on tried different rods and springs same issue. Put an older 625 Carter on and same issue secondary stumble, tried jetting up the 625 and stumble got worse just like the 850. So obviously not carburation has to be ignition, it does have the Chrysler electronic ignition and we did try a different orange box but no change, timing hasn't changed 12 degrees initial 35 total, so where do we look from here.
Secondary Stumble
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Adam
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Does the timing progress smoothly from 12 (12 initial seems high to me) to 35? (35 at what rpm?) Check the mechanical advance. Does it bind? Might try lighter springs Or different distributor...
4secondsflat.com has good tech articles and I believe will recurve your distributor, or sell you one.
4secondsflat.com has good tech articles and I believe will recurve your distributor, or sell you one.
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Chryco Psycho
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Could be ign or fuel but if it was working well before I doubt it is fuel related , could be bad plugs or wires or weak coil , I would reduce the timing curve so you can be around 16 * initial & 36* total , you might have to weld the slots in the advance plate to do this .
moparleo
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Is the vacuum advance connected ? You said that it "has developed" a stumble. What exactly does that mean ? Out of the blue with no changes on any parts or adjustments ? Just one day started to stumble ? Does this present itself during normal , daily driving or during hard acceleration?
Vacuum advance is not connected and never was. He has 4 Mopars and not one of them runs with the vacuum advanced hooked up. Nothing was changed just started happening. No matter what speed when he jumps on it she will stumble then take off
moparleo
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Don't get upset, just because he has never used the vacuum advance ( which is designed to handle just such a problem.) His car stumbles, not mine. Mechanical advance only, is designed for just foot to the floor driving. No stumble because the secondaries are always open.
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Tuning Tips
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Who said I was upset, it's the way he runs all his cars. I personally run mine connected and never had a stumble, I run Edelbrock carbs for the reason my buddy is having trouble with his Holley. When I first bought my car 14 years ago it had a Holley 800 on it and I never could get it to run. I even had a couple of the best Holley tuners in my area work on it and they couldn't get it to run, I got rid of it bought an Edelbrock and have never looked back. In fact I just upgraded to the new AVS-2 carb and the throttle response is incredible with the annular boosters, best street carb on the market.
moparleo
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Ditto with you. Edelbrock AVS on current 5.9 Magnum crate. Ran Thermo-Quad on previous 340 Challenger. Great carb. Never had luck on the street with a Holley. Susceptible to the tiniest bit of dirt. Had to remove metering blocks and blow out with air on a regular basis. Fuel filters between the tank and pump and pump and carb. Carter/Edelbrock Air Valve Secondary setup easy adjustment. Trouble free.
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