250-6 Fouling Plugs

Discussion in 'Technical' started by Craig Selvey, Jun 1, 2013.

  1. Craig Selvey

    Craig Selvey Indiana State Rep - MCCI Supporting Member

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    Here is what I have. My 1976 4-door Maverick seems to run and drive just fine, except that it will regularly foul the plugs. I have driven this car to Washington D.C and back, as well as Detroit Michigan and back. Not afraid to drive this car anywhere. I can normally get about 800 miles on the plugs before it will develop a slight, but noticeable miss. At this point I would remove the plugs, clean them, re-install and keep driving. It would normally take me about 2 months to put on 800 miles, since I don't drive this car everyday. Not enough to really bother me.

    I installed aftermarket cruise control. This requires a "pick-up" sensor to be installed on one of the spark plugs. The problem with this is, that if the spark plug has a "miss", it kicks off the cruise control. I have noticed this little "miss" happens after about 200 or 300 miles, maybe less, which means I really can't drive the car long distances without the cruise control constantly being kicked off. What good is cruise control if you really can't use it? This bothers me. I tried one of the "anti-foulers" thingys you put on the spark plug. Did not really help.

    Also...the car uses about a quart of oil every 600 to 800 miles or so. Doesn't puff smoke all the time, just at start up.

    When I bought the car, the previous owner told me the engine has been rebuilt.

    So....I decided to pull of the head and have it gone through. In two previous 6 cylinder Mavericks I had with the same problem, I did this and it fixed the fouling problem and fixed the oil consumption problem.

    So I take the head off, take it into the machine shop, and leave it to have gone through. The machine shop tells me after tearing down the head that he doesn't think the head is my problem, but also admits he is not a real mechanic either. He showed me the intake valves. Lots and lots of gunk on the back side. I wish I had a picture, but there was so much, it made me wonder how the car even ran at all. Black gunk, very hard, very crusty looking. He tells me maybe the rings did not seat when they rebuilt the motor, or that the ring gaps are all lined up, allowing oil into the combustion chamber. He said if that was the case, the tops of the pistons would look like the valves and be "wet" with oil. They don't look anything like the backs of the intake valves to me.

    Also, he said the umbrella valve seals were all in the "down" position...not riding the valve stems up and down. He said they would move very easily up and down the valve stem, which is why they were all "down".

    So, after saying all of this, look at the pictures and tell me what you think. The spark plug is after about 300 to 400 miles. They all look like this one, but this one is probably the worse.

    Thanks.
     

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  2. Craig Selvey

    Craig Selvey Indiana State Rep - MCCI Supporting Member

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    More pictures.
     

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  3. Craig Selvey

    Craig Selvey Indiana State Rep - MCCI Supporting Member

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    More details: I have removed all the smog equipment, including installing a re-pop exhaust manifold that has none of the smog provisions on it, and also removing the EGR and replacing with an early 250-6 carb plate with no EGR.
     
  4. mike75mav

    mike75mav Member

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    Did you do a compression check? If you have to take the head after 800 miles than its not the head. I would say that you have bad rings and maybe bearings. I seems to me you need to an overhaul on the block.
     
  5. Dave B

    Dave B I like Mavericks!

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    When was it rebuilt , 1980?
    Time to pitch that hoopty, for a V8.
     
  6. MikeG747

    MikeG747 Member

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    My son's 250 Comet was doing the same thing. I told him he had to use high octane gas. He admitted he was too cheap and using regular. When he used high octane he did not foul plugs. My :2cents:
     
  7. ford84stepside

    ford84stepside Lone Wolf

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    #2 & #3 exhaust valves look mighty oily compared to the rest of them, # 3 is the worst looking. Cylinders look good, cross hatch is still visible, so rings not seated good is a good possibility. I had a set of rings do that on an old VW one time. No matter what I tried, they would never seat fully. Can't remember if they were steel rings or moly ones, but whichever they were, i went back with the other kind and they sealed first time I cranked the engine. Memory just ain't what it used to be.....
     
  8. Craig Selvey

    Craig Selvey Indiana State Rep - MCCI Supporting Member

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    I did not do a compression check. Engine has WAY more than 800 miles on it since the rebuild. Car runs great....other than fouling the plugs. I would think I would have other problems if it was the rings??????
     
  9. groberts101

    groberts101 Member Supporting Member

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    as you mentioned above.. the tops of the pistons would be much worse off in the way of deposits if the rings were the main culprit here. The "tell" of an older Ford running factory umbrella seals is that little puff of smoke at startup. Ring seal issues will often result in larger puffs during heavy footed gear changes or higher concentrations of smoke at higher rpm's(as engine loading and dynamic cylinder pressure rises in each case).

    Many underestimate the amount of "oil pull" that even 15 inches of vacuum has on oil through the valve guides. The factory umbrella seals don't last much more than 30,000 miles from all that I've seen. Especially the cheaper "rebuilder specials" that many use to cut costs on basic stock rebuilds which can sometimes start leaking oil almost right away.

    Also consider that as the oil runs over, through, and then inevitably under the seals as the engine is running at higher rpm.. the seals start to get "stickier" and there is some slight pumping effect which only adds insult to injury when it comes to oil consumption issues that may already exist from guide/stem clearance and wear.. however slight it may be on a fresher engine.

    Do you still have the heads off the motor? If so.. this is the perfect time to spend the extra hundred bucks to cut the guides down for the positive style seals. Viton seals with metal reinforced bodies are usually best.

    And if not?.. then start kicking yourself right about now for not doing it when they were free of the block. Learn that lesson the hard way and never.. ever.. use those cheap factory seals on any engine you plan on keeping around to enjoy.

    PS.. if the heads aren't still free of the block and you don;t want the hassle of removing them again?(how long you plan on keeping the car should weigh in on that decision).. run 2 steps hotter on you plugs to avoid fouling them as quickly. Also moving to synthetic oil will considerably reduce burn off.. and therefore fouling of plugs as well.
     
    Last edited: Jun 2, 2013
  10. simple man

    simple man Member

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    I'll agree with " groberts101". Getting buildup on the underside of intake valves means oil is coming through the guides! What he said about the overhaul kits is also correct. Some of them have garbage for seals! If you had minimum blowby when your engine was running, you don't have an issue with your block! I'd get your head redone at a professional machine shop! :thumbs2:
    As a side note, some of your cylinders look quite lean ( pure white ). When you get your engine back together, pull the plugs after a few drives and see if they are still white. This could have been caused by an extreme buildup on those particular valves choking down the fuel mix. :)
     
  11. Craig Selvey

    Craig Selvey Indiana State Rep - MCCI Supporting Member

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    Thanks for the input, guys. The head is still off the car and and at the machine shop. It is a very reputable shop in town...actually recommended to me by another shop because they have the equipment to do the long 6 cyl heads. I will print off these responses and take them to the machine shop. He had already mentioned installing the positive style seals.
     
  12. Dan Starnes

    Dan Starnes Original owner

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    Are you running the hottest plug available? Yeah the short block can be worn and you can be getting some oil on the plugs. But I have run stuff like that for year. Hot plugs, non foulers, stuff like that has extended life of motors for me.
     
  13. Craig Selvey

    Craig Selvey Indiana State Rep - MCCI Supporting Member

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    Yes, I have run hotter plugs, as well as the non foulers. No real difference. I really feel the block is not worn out. But, as one can see and read, there are problems with the head.
     
  14. 71gold

    71gold Frank Cooper Supporting Member

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    gunk on the wrong side of the valve to be bottom end...:yup:
     
  15. injectedmav

    injectedmav Member

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    Positive type valve stem seals should take care of that issue. As the guys have mentioned, those umbrella seals are worthless. You may also find that you need to go back to the original heat range plugs when you go back together with it. Carbon/oil deposits on the backs of the intake valves will soak up the fuel and run the engine lean at times, especially startup until they get fuel soaked.
     

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