PCV fouling Spark Plugs?
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PCV fouling Spark Plugs?

  1. #1
    Senior Member Rivernut's Avatar
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    Default PCV fouling Spark Plugs?

    My Chevy 350 jet boat fouls plugs #3 and #6. I noticed that the Holley carb vacuum port for the PCV feeds into the dual plane rpm manifold adjacent to the fouling cylinders. The plugs are darker and black up the threads but not shiney or gooey. The engine runs at 4,400 rpm's for sometimes an hour at a time. It has consumed some oil, maybe 1 quart per 10 running hours. I have Profitm valve covers with factory style baffles, a generic GM PCV and a push-in breather on the other cover. Is this set up likely causing the fouling on the third plug back on each side? The other plugs are perfect, new rebuild.
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    Don't think so sound like you have clearance issues in those cylinders. Build up of oil residude from bad rings, bad oil seals or bad valve guides. I am assumeing it must smoke like hell when yo try to start it fresh or after it set assuming thso valves are open.














    if you use standard seals they are
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    E-7 Sheepdog (ret) SmokinLowriderSS's Avatar
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    That would be one hell of a lot of oil thru the PCV, I agree with the above, you've got oil controll problems related to rings or valves (seals and/or guides).
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    Senior Member Rivernut's Avatar
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    The engine is a Vortec 5.7 from a '99 crash and burn truck with less than 20,000 miles on it, cross hatching on cylinder walls, looks new. The heads were gone through by a reputable machine shop, new seals put in. Good compression 195-205 PSI on all cylinders. Running one heat range hotter than stock plugs AC R44LTS, Edelbrock RPM Air Gap Manifold, Holley 600 vacuum seconday, 66 primary jets, 0.070" secondary plate, 4.5 power valve, Crane Gold 1.5 roller rockers, 10 degrees initial timing, 32 degrees total timing, 160 degree thermostat.
    Last edited by Rivernut; 06-14-2009 at 05:52 AM.
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    Senior Member Delemorte's Avatar
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    dont know if this is your issue or not but i had a similar problem with 3 and 6. Turned out my distributor cap as not seeated properly and just so happned to end up on those cylinders. 3 and 6 fire back to back so that was my problem. Mybe those cylinders arent firing properly.


    If you run WOT for a hour strait are you losing a bunch of oil thru the push in breather? If hes not burning up the oil maybe hes just spittin it out. I know my SBC gets all kinds of nasty up there just after an afternoon of mixed driving.
    Quote Originally Posted by jetboatperformance View Post
    the ensueing fire would likely be extinguished by the sinking however
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    Senior Member gregb's Avatar
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    I doubt it's the PCV. It would be easy to test the theory, just cap it off and run with a breather in each cover, (you would probably also find the inside of the pcv hose to be an oily mess). If it continues I'd pull the intake and look for signs of leakage.
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    Junior Member 74miller's Avatar
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    you might check your firing order. said #3 and #6 and then also 3rd one back on each side? looking at the front of the motor chevy runs 2-4-6-8 on the left and 1-3-5-7 on the right, sometimes you cant feel the mis at higher rpms.
    you could also check for a misfire by letting somone else run your boat and you could clip your timing light on the cylinders that a fouling. check at different rpms if it is in the ignition you will see the light flashing unevenly.
    what distributor and cam are you running? gm has distributor gear problems on those motors and the timing cant be set with a light on the '99 distributors
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    Senior Member GT Jets's Avatar
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    You more than likely have a leaking intake manifold from the underside, extremely common on a 350 Vortec.

    The first thing I would do is remove the intake and see what the gaskets look like, I have seen over a dozen leaky intakes on the Vortec configuration.

    Make sure the torque sequence is followed to a tee.

    People very seldome torque these correctly...

    Good luck!

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    Quote Originally Posted by Quickjet View Post
    Put a 300 on the back of it, Flywheel it and a nosecone. $15,000 later you'll have a 65 mph pile of shit......
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    Junior Member 74miller's Avatar
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    I would agree that the proper torque is the only way they will hold.
    Just seems a little odd that the problem is on the 3rd cylinder back on both sides.
    We do 2-3 intake sets on those trucks a month but most of them for coolant leaks (dexcool plays hell with air in the system).
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    Senior Member Rivernut's Avatar
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    Oops, cylinders 5 and 6 are the ones. I had tried going up one heat range to AC R44LTS. The plugs are cleaner than with the AC MR43LTS plugs but may be too hot. I looked under the microscope at them after a day of running and the porcelain has small white beads, only viewable with the microscope. I guess it is starting to melt and bead-up. Nobody has posted this online - little beads. I looked...a lot! Anyway, the manifold gaskets are these special Felpro marine gaskets. They are made out thick black rubber with some aluminum sheet embeded in them. Maybe I did not torque them enough. The Vortec truck stock gaskets are the rigid plastic ones requiring inch pounds. I torqued these marine ones to about 10 ft. pounds. I could not find a proper torque value for non-plastic Vortec intake gaskets. Any of you know the gaskets I'm referring to? The engine does not run like it has an intake leak. It idles very smooth @ 600 RPM's with the idle screws 1.25 turns out. Yesterday it used 3/4 of a quart of oil on a 115 mile trip using about 55 gallons of 93 octane.
    Last edited by Rivernut; 06-21-2009 at 04:59 PM.
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    Senior Member gregb's Avatar
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    Unfortunately the only way you are going to find out if it's an intake leak is to pull the manifol. It won't necessarily make it run bad if it is leaking, but if the gasket didn't seal properly it will let a lot of oil thru.
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    Go to the Home Depot/Lowes and over to the air tool section and pick up a cheap air line air/oil separator and a couple of barbed hose end fittings and place it in the pcv line to see if there's any oil getting past the pcv valve. If there is it'll catch it. We've had to do that to several LS1 engines to fix oil consumption issues. The small ones like this are ideal.
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    Last edited by cordog009; 06-21-2009 at 04:54 PM.


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    Senior Member GT Jets's Avatar
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    Quote Originally Posted by cordog009 View Post
    Go to the Home Depot/Lowes and over to the air tool section and pick up a cheap air line air/oil separator and a couple of barbed hose end fittings and place it in the pcv line to see if there's any oil getting past the pcv valve. If there is it'll catch it. We've had to do that to several LS1 engines to fix oil consumption issues.
    That right there is a helluva idea...Gotta purge something from the memory to remeber that one...

    GT
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    Quote Originally Posted by Quickjet View Post
    Put a 300 on the back of it, Flywheel it and a nosecone. $15,000 later you'll have a 65 mph pile of shit......
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  16. #14
    Senior Member Rivernut's Avatar
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    I bought a Husky Water separator last week at Home Depot but the drain valve didn't close on any of them, maybe they need to be under pressure. I returned it and have been looking for a better one, maybe even a real catch can from Summit, Jegs, etc. Anyone have one that stays shut until you drain it? What should I torque the manifold to? It's an Edelbrock Air-gap RPM with the marine thick black rubber gaskets.
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