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Discussion Starter #1
Recently when I was driving my motor just started to run really rough. Its not backfiring or anything, It feels like Its has a slight miss and or loading up with fuel. EVERYTHING is new (less than 100 Miles) New wires, New Plugs, Msd 6al, blaster 2 coil, pro billet dizzy. I pulled the plugs and they dont have any visible defects. I put a bottle of b12 in the gas and no difference. Before the b12 the exhaust smelt "different" and I can see a cloud of fumes when driving. Timmimg is still correct. Could a carb rebuild be in order? Its not getting any worse but its still there. Any thing that yall can suggest would help.

Chris
 

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Are all the cylinders burning fuel, each exhaust hot as shown with a temp gun?
Vacuum gauge steady (good) or shaky (bad)? Valves too tight, too loose, misfire, leaky intake/carb gasket, etc?
Fuel level alittle too high?

Alittle more initial advance?
 

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What carb are you running? Blown Holley power valve? If you are dumping fuel, it could be float level as well. To see if you have a leak at the carb base, spray some quick start fluid around the base, if the rpm goes up you have a leak.

alan
 

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Check the plugs. If you lost a cam load, hung a valve, or had an ignition problem it would show up on the plugs. If all the plugs are the same or if they follow the pattern of the intake runners you probably have a problem higher up the intake path or down the exhaust path.
 

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Discussion Starter #8
Sry for the delayed reply. But, I've changed out the gaskets and added a 1" spacer. I had the carb off (holley 670 avenger) for a couple of dayscand when I put it back on it ran great for about 20 miles or so then same problem. I check the resistance in the plug wires and the were with in msd specs. I also checked the plugs and the back 4 on the motor had unburnt fuel on them. So then I checked the float levee and they were good! I'm lost now. Maybe some trash in the nettle and seat? Or could it be that power valve? Any other suggestions would be great.

Thanks,
Chris
 

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If it were the power valve, you wouldn't get 20 good miles before it went to heck. It would run poorly right out of the gate.

Guys, if the 4 rear cylinders are wet, would that indicate dumping of fuel in the secondaries?

alan
 

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Discussion Starter #11
I took out the neetle and seat on the primary, cleaned it and reinstalled it and turned 1/4 turn passed from when I took it out. ITS A MILLION TIMES BETTER! But there is still a small stumble when accelerating hard. I'm thinking that the spark plugs are fauled out. Should this fix it self or should I go and change them out anyway.

Chris
 

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First, pull the plugs, clean them with a brass brush and some fine emory paper on the electrodes. Regap the plugs and install them.

You need to check your secondaries to see if they are dumping open to soon and causing the bog. More than likely, it is the accelerator pump.

I would look to the shooter of the accelerator pump. You want to see gas squirt just as as soon the carb is moved open. If it does, great, now you have to experiment with the pump shot by switching the plastic cam for a larger pump shot. In some instances, it might be necessary to go with a bigger squirter nozzle.

Check here:

http://www.holley.com/types/Pump Discharge Nozzles.asp

and here:

http://www.holley.com/types/Accelerator Pump Kits and Service Parts.asp

I would get the kit with the assorted cams so you can inch up on the solution.

good luck

alan

P.S., if that doesn't solve it, I would look at the distributor advance curve.
 

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Discussion Starter #13
First, pull the plugs, clean them with a brass brush and some fine emory paper on the electrodes. Regap the plugs and install them.

You need to check your secondaries to see if they are dumping open to soon and causing the bog. More than likely, it is the accelerator pump.

I would look to the shooter of the accelerator pump. You want to see gas squirt just as as soon the carb is moved open. If it does, great, now you have to experiment with the pump shot by switching the plastic cam for a larger pump shot. In some instances, it might be necessary to go with a bigger squirter nozzle.

Check here:

http://www.holley.com/types/Pump Discharge Nozzles.asp

and here:

http://www.holley.com/types/Accelerator Pump Kits and Service Parts.asp

I would get the kit with the assorted cams so you can inch up on the solution.

good luck

alan

P.S., if that doesn't solve it, I would look at the distributor advance curve.
I already changed out the cam pump and squirter and it ran perfectly! then after two weeks or so it started to go downhill from there. I ordered some new plugs and a neetle and seat assembly. Im still leaning towards the neetle and seat assembly. Like I said before I over tightened the neetle and seat a 1/2 a turn more than when it came out and It ran great. But its slowley starting to start missing again. I'll change those things out and I'll keep yall informed.

Chris
 

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In post #11 you said it was running much better after adjusting the needle and seat. But now it is starting to deteriorate again? Are the plugs black and sooty? Damp with gas? I am wondering if the plugs are the right heat range. If they are too cold, they will foul out.

alan
 

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If the back four are sooty, the secondary fuel level may be too high.
If the engine is running rough after running good for some time, then I agree with Alan, hotter plug is needed.
 

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Here is how to set float level in a Holley. If your float level is too high, it could dump fuel into the manifold and foul the plugs. We need to take this step wise and eliminate the basics. One step at a time. Check both front and rear bowls.

http://www.stockcarracing.com/techarticles/general/scrp_0809_holley_carburetor_float/index.html

And this from the Holley website:

QUESTION How do I adjust the fuel level on my carburetor?
ANSWER Setting the fuel level should be the first thing you do before attempting to make any further adjustments.The float level should put the fuel level just below the bottom of sight plug hole. You will make the adjustment with the vehicle on a level surface and the engine idling. You will first remove the sight plug, then to make your adjustment you will need to loosen the lock screw on the needle and seat. This will allow you to turn the adjusting nut to raise or lower the float level. Each hex flat on the nut will change the float level approximatly 1/32". When you have the fuel level just below sight plug hole you will then tighten the lock screw and reinstall the sight hole plug. Make sure you have a shop towel handy in case you have any fuel leaks from the Sight plug or needle and seat adjusting nut.

alan
 

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Holley sold some carbs that are known to fail due to poor plating process in the metering blocks. See if yours is one of them.
 
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