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Old 08-14-2009, 05:58 PM
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Motor suddenly goes super rich...

Driving down the local boulevard this afternoon my hot rod suddenly started running really rough, and when I let up on the loud pedal it quit. I got it started again by holding about half throttle, but it was really ragged and if I let up on the throttle at all it would start to unwind. I noticed when I was stabbing it to keep it running, big plumes of black smoke were coming out the side pipes. I checked the distro and it hasn't come loose. I checked the fuel pressure gauge and it's right where it's always been (5.5#) It appears to me that it has suddenly gone very rich.. I took off the caps on the vacuum nipples of both carbs and it will idle that way, but very ragged with a strong fuel smell in the exhaust. I'm thinking junk in one or more float valves. What other possibilities?

Here's the hot rod...


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Old 08-14-2009, 06:06 PM
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Ooops, sorry, forgot the rule about motor specs...

355 sbc, moderately built
BDS 6-71 at 1:1 for 6#
Comp "blower" roller hydraulic cam
2x Edelbrock 1405s (600 cfm) re-jetted for the blower
MSD ignition (mag pick-up distro, 6AL box, Blaster II coil)
Holley Blue electric fuel pump and regulator set a 5.5#
Fram in-line cannister-type fuel filter ahead of the pump

Motor has performed flawlessly since completion three years ago.
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Old 08-14-2009, 06:16 PM
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Check your throttle linkage for hanging up. Your throttle return spring could be weak also.

I can't tell from the picture, how it is set up, and what kind of ends are on the linkage. Lube the points, and where the accelerator pumps attach.
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Old 08-14-2009, 06:17 PM
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I would think you are looking in the right area. Other possibilities are hung step-up piston in the Edelbrock carb.
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Old 08-14-2009, 06:21 PM
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Dirt in the carb needle and seats. (flooding) stuck power piston/mettering rod (good call).
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Old 08-14-2009, 06:24 PM
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Linkage is all good... definitely something in the fuel metering chain. Hadn't thought about a hung metering rod. Guess I gotta pull the tops off the carbs, eh?
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Old 08-14-2009, 06:37 PM
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Quote:
Originally Posted by XNTRCI-T
Linkage is all good... definitely something in the fuel metering chain. Hadn't thought about a hung metering rod. Guess I gotta pull the tops off the carbs, eh?
You have to be Canadian to say EH!, eh, Hoser! Or at least been to a hockey game or 3 in Toronto or Montreal. I'll allow it one time if you've been to a hockey game in Buffalo against the Leafs. Extra bonus points of you've been to a minor hockey game in Peterborough or Sudbury Ont.
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Old 08-14-2009, 06:42 PM
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Formerly married to a Canadian, eh. Still go fishing in northwestern Ontario every summer, eh.

Last edited by XNTRCI-T; 08-14-2009 at 06:58 PM.
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Old 08-14-2009, 06:43 PM
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You don't have to pull the top off the Carbs. just the screw and plate covering the metering rods, and step up springs. You should be able to tell if a step up piston is stuck, by the amount of push from the spring as you remove the cover. If these are fine, start it up, or turn on your fuel pump, and look for excessive fuel out of the main jets. This could be something between the needle and seat.

For grins, remove a easy spark plug to get to, and check for a good spark. I have seen the center coil post on the inside of the distributor cap erode away.
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Old 08-14-2009, 07:00 PM
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Life time honorary "Hosehead" membership, if you go to a Kim Mitchell beer party at the Kee to Bala. Then go fishin!
http://www.thekee.com/
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Old 08-14-2009, 07:11 PM
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LMAO! I'm a little tamer than that. We fly into Minaki and then float plane out to some remote lakes to the northwest. One Man, Moosehorn, Eagle Nest (actually in eastern Manitoba) and the like. No telephones, no cell phones, no intarwebz, no TV... just nature... it's spectacular in its lack of... people. Just nature... bald eagles, red-tail hawks, beavers, otters, black bears, moose, deer... and big frickin' fish!!
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Old 08-15-2009, 12:42 PM
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Quote:
Originally Posted by XNTRCI-T
I'm thinking junk in one or more float valves.
Man I'm good! That's exactly what it was. Little shard of metal stuck in the pax side float valve of the front carb. Checked all the others plus all the metering rods just to be sure. We're good to go, except the spark plugs are majorly carboned up. Might be a good time to try a set of E3s.
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