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Old 10-29-2008, 02:18 AM
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Holley over rich condition

As stated in another thread, I started my 331" sbc last week, it sounded very good and all went well until I pulled the plugs to check the burn. I had let it idle down to about 800 rpm to cool down a little so this was basically a rich idle condition, they were all black and soot covered.

I tried to adjust the idle mixture screws on the Holley but even turning them in all the way did nothing, the engine kept running with no change in rpm. I'm figuring a blown power valve (brand new Quick Fuel Pro Vac carb) so I made a trip to Napa for a new Holley p/v. After installing it I tried to fire the engine but now it won't start at all, just loads up and blows a little black smoke.

I pulled the plugs and they are just dripping gas, pulled the carb and the plenum is covered in gas????? So now I'm figuring what the hell is going on here. After blowing as much gas as possible out of the engine I re-installed the original p/v that I thought was blown and the engine started after a few revolutions and started to run pretty good after it cleaned itself out.

Again I screwed the idle mixture screws in all the way and nothing! but now I notice the engine is surging, almost like a blower motor. The vacuum gauge is going from 11" to 14.5" and it also showed the surge on the oil press. gauge. I looked at the fuel press. gauge and it was very erratic showing 0 and then it would jump up to 9.5 lbs. which is too much. The fuel pump is a Holley mech. #12-327 (5-8 psi) brand new and says is does not need a press. reg. (????) I also noticed gas dribbling out of the right front booster leg at high idle.

I called Quick Fuel and he said theres no way the engine should run with the mixture screws shut down unless the p/v is blown. He also said the fuel press along with the blown p/v is probably the problem and suggested I install a press. reg. So before I either install the reg. or buy a stock AC or Carter fuel pump what do you guy's think? Could the excessive fuel pressure be blowing the needle off the seat or causing some other rich condition? Kinda got me stumped......any questions or idea's? thanks Dave

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Old 10-29-2008, 04:28 AM
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Can you put a pressure gauge on and check pressure? 61/2-8 psi should be okay. I use a Carter M6900 on my 400HP 327, which is preset at 6psi. Plenty. Check and see if the PV gasket is good, not torn, and that the PV is not overtightened. Possibly a piece of junk under needle and seat?
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Old 10-29-2008, 04:29 AM
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anything over 7 psi max is bad! ( fuel pressure)
any time the fuel pressure fluctuates tells me your fuel pump is going south.
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Old 10-29-2008, 09:04 AM
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Holley over rich condition

you may need to replace the o-rings on needle seats , how old is the carb and how long has it set before use ?after being used .
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Old 10-29-2008, 08:51 PM
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To answer the questions...it has a fuel press. gauge and as I said it reads very erratic, from 0 to 9.5 lbs. with the engine running. Brand new Holley 110 gal. pump, which is probably overkill, an 80 gal. would be just fine I think.

The carb is brand new, was run tested on an engine and then shipped to me. It has sat in the box for 8 yrs. before I started the engine last Friday.

The new p/v I got had the gasket in 2 pieces when I pulled it back out of the metering block, it wasn't torn but like 2 seperate gaskets.

The secondary metering block doesn't have a p/v or idle mixture screws just jet extensions into the bowl. Could there be something wrong from that end?
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Old 10-29-2008, 11:24 PM
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I had the same problem with my 650 dp. I even changed the jets, thinking that was causing the rich condition. What happened was the secondary float was adjusted too high. I took the sight plug out and fuel came out. I adjusted the float down on both the front and rear bowls and now I'm running at a lean condition and no more sooty plugs. I may even have to go one step higher on the jetting. Check out the float adjustment, might be your problem. The gasket from the p/v is split in two. That is a common problem with p/v gaskets. You need to replace that for sure, because that will cause problems. It's suppose to be a one piece gasket.
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Old 10-30-2008, 01:09 AM
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Ok I'll give that a shot, I put the good gasket back on the new p/v.
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Old 10-30-2008, 06:27 AM
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Holley over rich condition

on them gasket's that stick and pull apart , spray some pam cooking spray on them , it works good on that problem , along with keeping your cholesterol down .

8 year sitting on shelf , they don't run as new .
take the fuel level plugs out and if it's not trickling out gas while running , shut off motor and see if it begins to run out , them needle seat o-rings dry up from sitting after gas has run by them .

when it is running , do you hear a like crackling noise in carb , i had one that did this and it was gas getting by and just enough to make the idle run erratic .
it was a bad carb casting in meter block .
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Old 10-30-2008, 10:12 AM
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Seen it before!

Carbs cannot sit for 8-years and be perfect. Two bad things happen: 1. the O-rings on the needles and seats get hard and compressed. Any fuel pressure over 5-lbs will make them leak fuel past the seat filling up the bowl and flooding or at least running terribly rich. 2. The power valve diaphram gets brittle and hard and fails to function. The power valve serves to enrich the fuel mixture about 5-times over the normal jetting for full power under low vacuum. Use a number 65 power valve with a NEW high flow gasket (from Summit or Jeg's). It will remain closed until engine vacuum drops to 6.5-inches hg. If you bought a kit, it comes with new needle and seat O-rings but they can be ornery to put on. If you don't, install NEW needles and seats! I assume you have center hung float bowls. You can initially set the float level by holding the bowl upside down and viewing the top of the float across the 2-hinge mounting screws. Adjust until the float aligns with the bottom of the screws. Any fuel pressure over 6.5-lbs is not good on the street. A regulator is always a good thing too. I would set it at 5-lbs and then see what the gauge reads at WOT down the road. If it drops below 3-lbs, raise the pressure to 5.5-lbs. The higher the fuel pressure, the lower the float has to be. No fuel should come from the boosters until the throttle is opened enough to transition from the idle transfer slots-usuallu a tip-in at about 30-degrees of throttle opening. Good luck. You can also get me at pfogel@tampabay.rr.com
Pat
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