oil fouled plugs

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    Author Topic: oil fouled plugs  (Read 8274 times)

    Offline Aussie Challenger

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    Re: oil fouled plugs
    « Reply #30 on: March 15, 2011 - 06:09:54 AM »
    Generally there is pressure going up an exhaust guide, inlets have a vacuum when opened so excess oil can be drawn into combustion chamber.   :2cents:
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    Dave


    Offline Kapteenikosmos

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    Re: oil fouled plugs
    « Reply #31 on: March 15, 2011 - 07:55:14 AM »
     :iagree:

    With somewhat sensible cam shaft the exhaust shouldn't draw any significant amount of oil through guides. It's the intake valve seals that usually cause the blue smoke if the piston rings are in good shape and sealing correctly.
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    Ville

    1967 six banger Mustang
    1973 Challenger (under restoration)
    1997 Lincoln Mark VIII LSC (daily driver)

    Offline 72cudamaan

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    Re: oil fouled plugs
    « Reply #32 on: March 15, 2011 - 08:44:46 AM »
    Sorry guys, I don't want to start an argument, but when your piston rings are sealing correctly, on a down stroke they will cause a suction. If the exhaust valve is open then the suction will pull air and/or oil down the guide. I am not narrow minded about this, so if anyone can refute this, then I am all ears.  :grinno: 
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    Andy  (phukker whither)

    Offline Kapteenikosmos

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    Re: oil fouled plugs
    « Reply #33 on: March 15, 2011 - 05:42:25 PM »
    Quote from: 72cudamaan on March 15, 2011 - 08:44:46 AM
    Sorry guys, I don't want to start an argument, but when your piston rings are sealing correctly, on a down stroke they will cause a suction. If the exhaust valve is open then the suction will pull air and/or oil down the guide. I am not narrow minded about this, so if anyone can refute this, then I am all ears.  :grinno:

    Ok, I'll try to explain my point of view without causing any real arguments, hopefully  :rofl:

    In theory it would suck oil through exhaust valve stem if the valve is open and the piston is going downward, but the exhaust valve is there to open a passage to exhaust gasses from the cylinder. So during normal operation the exhaust shouldn't open so that there is a suction in the cylinder. With overlap and other cam shaft features the exhaust will open while the piston is still going down ward but during that time there should be some  overpressure on the cylinder. Otherwise you would be sucking exhaust from the exhaust pipes inside the cylinder which really isn't very good powerwise. The emission hippies invented an egr valve for that purpose.

    Also to create any real suction inside the cylinder while the piston is traveling down and the exhaust valve is open, your exhaust needs to be pretty much clogged up. You are, after all, sucking exhaust gases through 3 inch pipe or so.



     
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    Ville

    1967 six banger Mustang
    1973 Challenger (under restoration)
    1997 Lincoln Mark VIII LSC (daily driver)

    Offline Aussie Challenger

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    Re: oil fouled plugs
    « Reply #34 on: March 16, 2011 - 06:20:21 AM »
    Quote from: Kapteenikosmos on March 15, 2011 - 05:42:25 PM
    Ok, I'll try to explain my point of view without causing any real arguments, hopefully  :rofl:

    In theory it would suck oil through exhaust valve stem if the valve is open and the piston is going downward, but the exhaust valve is there to open a passage to exhaust gasses from the cylinder. So during normal operation the exhaust shouldn't open so that there is a suction in the cylinder. With overlap and other cam shaft features the exhaust will open while the piston is still going down ward but during that time there should be some  overpressure on the cylinder. Otherwise you would be sucking exhaust from the exhaust pipes inside the cylinder which really isn't very good powerwise. The emission hippies invented an egr valve for that purpose.

    Also to create any real suction inside the cylinder while the piston is traveling down and the exhaust valve is open, your exhaust needs to be pretty much clogged up. You are, after all, sucking exhaust gases through 3 inch pipe or so.



     
       :iagree:  That explains it correctly, well said.
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    Dave

    Offline 72cudamaan

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    Re: oil fouled plugs
    « Reply #35 on: March 16, 2011 - 08:35:32 AM »
    OK I'll buy that.   :cheers:
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    Andy  (phukker whither)

    Offline willard

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    Re: oil fouled plugs
    « Reply #36 on: March 16, 2011 - 10:20:49 AM »
    Well, in my case I was thinking about oil dripping into the cylinder via the exhaust guide when the motor is off. In our old russian engines in off road cars there were no exhaust stem seals in the rebuild sets - they were not necessary.
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    1970 383 R/T SE

    Offline Kapteenikosmos

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    Re: oil fouled plugs
    « Reply #37 on: March 16, 2011 - 11:09:22 AM »
    Quote from: willard on March 16, 2011 - 10:20:49 AM
    Well, in my case I was thinking about oil dripping into the cylinder via the exhaust guide when the motor is off. In our old russian engines in off road cars there were no exhaust stem seals in the rebuild sets - they were not necessary.

    Might be possible if the stems are badly worn. In any case it shouldn't drip much because when the engine is shut down the oil would return from the heads back to oil pan so the valve stems are not submerged in oil. I don't think that they will submerge even if redlining the engine? The return holes on the heads are quite big after all.

    In your case it might be that all those small different things contribute into the amount of oil getting inside the piston chamber and the whole sum is the fact that causes the problems? And/or the piston rings aren't seated properly. Hopefully you will find what is the problem. I have similar 383 with the same pistons you have and so far it seems to run ok, though I've been running it for only few hours so far.

     
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    Ville

    1967 six banger Mustang
    1973 Challenger (under restoration)
    1997 Lincoln Mark VIII LSC (daily driver)

    Offline willard

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    Re: oil fouled plugs
    « Reply #38 on: March 24, 2011 - 10:43:58 AM »
    Ok, engine assembed brand new plugs and new repop plug wires. Car is very nice to drive, no smoke on acc/deceleration so probably rings are fine. I drove 60 miles yesterday with no problems at all. Definitely runs better than jsut after the rebuild.
    Today I wanted to wash the car and when I fired her up a nice cloud of blue smoke appeared in the mirror. So this is the oil dripping via the guides.
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    1970 383 R/T SE

    Offline willard

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    Re: oil fouled plugs
    « Reply #39 on: December 27, 2011 - 02:08:00 PM »
    Over half a year ago and 2000 miles later. 1000 miles ago I swapped heads to brand new stealths. Unfortunately the problem returned. As valley pan was sealed well, heads checked, it's rings...  moreover car uses a quart of oil every 200-300 miles and gets 10-9 mpg. No heavy smoking during driving but lots of it during startup.


    Thanks guys for all your suggestions. I'm pissed off and even dont want to disassembly the engine, maybe next year I'll buy a stroker kit and will rebuild the block again.
    If anone wants to have his engine rebuild by Normcar (www.normcar.pl) shop in Poland I strongly recommend to avoid them.
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    1970 383 R/T SE

    Offline Chryco Psycho

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    Re: oil fouled plugs
    « Reply #40 on: December 27, 2011 - 05:43:40 PM »
    a qt of oil in 300 miles should not be guides , either the rings are installed with all the gaps lined up or excessive ring gap possibly std rings in an overbored engine or the pistons are just way loose in the bores. No matter how you look at it the engine has to come apart  unfortunatly .
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    Challenger - You`ll wish You Hadn`t

    Offline LAA66

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    Re: oil fouled plugs
    « Reply #41 on: December 27, 2011 - 10:02:51 PM »
    Quote from: cwestra on February 25, 2011 - 07:10:43 AM
    I was thinking the same thing on the honing.  Seems like there should a greater angle between the hatching.  Closer to 45°.

     

     My first thought also, honing cross hatches look pretty far off. Plus the cylinder bores are kinda "shiny"

     I had the same problem with a Chrome ring rebuild (which uses another hone process different  than Moly.) They never set though. Even after the Ajax down the carburetor treatment. :grinno:
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