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Old 02-25-2013, 03:14 PM   #1 (permalink)
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Default Sputtering and stalling

I think i have two different issues going on, and wanted to get a few opinions. First: When i get on the gas really hard, it sputters... usually around 3k rpm or so... usually just before it shifts. My question is, would it feel like that if I had the wrong secondary spring in? Crashing in too early or late? What does that actually feel like?

The stalling... happens when I have to come to a stop after getting on it hard... ie. secondaries opening (I think). I think this may be a flooding condition... I have 70 jets in the primaries, and am going to switch them to 67s. 73s I believe in the secondaries.

This is all on a 351W, with 4 bbl intake, Summit 4 bbl 600crfm carb. Timing is between 12 and 14 intial, but the engine won't run if I drop that down any. Also have a pertronix III distributer with a flame thrower coil... getting just over 14V (pink wire bypassed). Choke is electric and fully opened and functioning properly, fuel pressure is 5 - 7... vacuum is between 12 - 14. Tranny is FMX.

As usual, and any all help is appreciated.
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Old 02-26-2013, 03:00 PM   #2 (permalink)
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Forgot to add I have Hedman headers w/ 3" exhaust, 30" glasspacks.

To add: the sputtering is more like a mild bucking... I'm sure I'm not describing it properly. It's avoidable if I don't mash down on the gas, so the car is drivable... just no fun what-so-ever.

The stalling... the car will start right back up again (not overheating and needing to cool), but it does take a few seconds of turning over to fire back up. I know I'm missing something... just need a few ideas of what else to look at.
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Old 02-26-2013, 03:09 PM   #3 (permalink)
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Spurtering imo not vacuum spring related. sounds more like an advance issue

Stalling issue. soudns like you need the anti stall solinoid/dashpot.
you can bump up your idle about 300 rpm just to see if it stays running
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Old 02-26-2013, 03:51 PM   #4 (permalink)
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Quote:
Originally Posted by Blues Power View Post
Spurtering imo not vacuum spring related. sounds more like an advance issue

Needs more advance? I've reset it a few times, using different methods, all to 12 degrees, then bumping it up turning the distributer to about 14. The engine just plain old won't run any less. I wonder if maybe the chain jumped, and I'm really set way low? Any tips on investigating this?

Stalling issue. soudns like you need the anti stall solinoid/dashpot.
you can bump up your idle about 300 rpm just to see if it stays running


Stupid question here: anti stall solinoid?

I can bump the idle some... right now it's around 1000 rpm in park and drops to 650 - 700 or so in gear, but I wouldn't want it too much higher than that.
Thanks for the thoughts
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Old 02-26-2013, 05:07 PM   #5 (permalink)
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Had similar issues here. It was a bucking sensation when accelerating hard. I suspected secondary spring too, so I disconnected the rod that goes from the diaphram to the secondary throttle plates. That pretty much cured it. I'm sure the secondaries were opening too soon, from my readings up on this symptom. So I bought the quick change kit and a bunch of springs. It turns out the 'middle' grade spring was in there and the 'out of box' specs had said it should contain the stiffest spring, color black. Changed the spring to black and all is well!

Also cured an off idle stumble with more timing. Timing was set at 13 deg and I was told to go to 20. I really didn't think this would work but its an easy fix if it does. Sure enough, that cured about 90% of the off idle stumble. Still starts fine when hot and no overheating.
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Old 02-26-2013, 08:56 PM   #6 (permalink)
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Thanks greg. I'll give that a shot... maybe not straight to 20, but maybe bump to 15, 18, etc. I'll also try droppkng in the black spring as well.
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