Register now to get rid of these ads!

Technical Weird Problem with One Flathead Spark plug fouling

Discussion in 'The Hokey Ass Message Board' started by Petejoe, Jul 11, 2019.

  1. Petejoe
    Joined: Nov 27, 2002
    Posts: 9,954

    Petejoe
    ALLIANCE MEMBER
    from Zoar, Ohio

    Before I get serious and start tearing things apart, I wanted to pass this by you guys.

    Rebuilt flathead has run perfectly for Three years now.
    Installed taller banjo gearing this spring. Other than that there have been Absolutely no electrical or mechanical changes made to anything on this setup.
    MSD ignition, Running the two outer bank Strombergs on this manifold.
    Using NGK B6L plugs. set at .025 all the way up to .040.

    Symptoms.
    The one plug fouls out within 10-15 miles after installing the new plug or cleaning the old plug.
    Plug seems more like dry carbon vs oily carbon.
    Most of the time, the miss is only evident during moderate acceleration. Not during high rpm acceleration.
    All the other 7 plugs are a perfect tan color.
    Maybe another clue??? The left bank ( the location of this fouling) slightly backfires through the exhaust during deceleration. The right bank rarely does this.
    The Number 5 cylinder is the only location of this fouling.

    What I've tried thus far.
    B6L plugs. set at .025 all the way up to .040.
    Replaced the spark plug wire from distributor to plug.
    Slightly leaned out the idle circuit only on the front carb.

    What I haven't done yet.
    Tested the new spark plug wire resistance.
    Advanced the timing
    Pull the cap and check for cracks or wear
    Tested for a vacuum leak.
    Performed a compression or leak down test.

    Am I missing something here??
    If I find the cap is good , Could the MSD somehow be weak at one cylinder ?
    Frustrating. Especially since this engines been running perfectly since its installation.
     

    Attached Files:

    Last edited: Jul 11, 2019
  2. Truckdoctor Andy
    Joined: Jan 13, 2017
    Posts: 707

    Truckdoctor Andy
    Member

    Have you checked compression on the fouling hole? How are the valve clearances? I seriously doubt you would have an ignition problem on just one cylinder unless that terminal in the cap is somehow damaged.


    Sent from my iPhone using The H.A.M.B. mobile app
     
    rockable and RMR&C like this.
  3. Things to try that are free or inexpensive before taking the engine apart. HRP

    Have you check your spark plug wire, It may have a problem, you could test it by switching out another wire, maybe try a hotter plug or you might try a non-fouler adapter, I used one on a old panhead and to my amazement it worked. HRP
     
  4. Petejoe
    Joined: Nov 27, 2002
    Posts: 9,954

    Petejoe
    ALLIANCE MEMBER
    from Zoar, Ohio

    Thanks for the advise you two.
    As stated. I haven’t begun any tear down yet. But did install a new plug wire. I first thought that was the problem but it wasn’t.
    I need to pull the (hard to reach) distributor cap first. I’m thinking it may be the problem. Yes I am first doing the easy stuff.
    Hell of a time to tear into an engine at driving season.
    Danny. Never heard of a non fouler adapter. I’ll have to look into that.

    More info.
    I installed a new plug and dropped the gap from 025 to .015/020 and noticed a 50% improvement.
    It ran perfect for 15 miles at high rpm on open road then began a slight miss at low rpm. But bringing it back to a high rpm @ 60 mph cleared the carbon and it ran well again. An occasional miss at low rpm continued for the next 30 miles but at high speed no miss. Not even a flutter.
     
    Register now to get rid of these ads!

  5. You cannot make something from nothing. That carbon came from someplace? The other cyls are not having problems. So its gotta be the piston and or rings on the offending cyl. maybe a gummed up stuck ring. Fill the cyl with a mix of acetone and diesel. or MM oil . and let it soak a couple of days. then turn it until both valves are closed. mahe a fitting from old spark plug to apply air pressure to the cyl. hook it up and put as much air pressure as you can into the cyl. that will force the mix past the rings and might blow any crud out. change the oil and drive it. If it continues you gotta tear it down. I doubt its the valve guides.
     
    Petejoe likes this.
  6. Petejoe
    Joined: Nov 27, 2002
    Posts: 9,954

    Petejoe
    ALLIANCE MEMBER
    from Zoar, Ohio

    I agree Old Wolf.
    Yes if my cap is good I do have a cylinder issue.
    Carbon is from unburned gas and I need to find the cause.
    I’ll definitely try the fix you suggested once I’m positive it’s not an electrical resistance issue.
    Thanks so much for tip. I’ll let everyone know what I find as soon as I get there.
     
    Old wolf likes this.
  7. Man, I thought I posted a photo, here ya go, they are available in different sizes. HRP

    non fouler.jpg
     
    Petejoe and Old wolf like this.
  8. those are non foulers they lower the compression about a CC worth. they remove the plug from the combustion chanber. They are mainly for engines that are burning oil.
     
    Kan Kustom, Petejoe and Jalopy Joker like this.
  9. Thinking back . I remember about 50 years ago I bought a black 61 ford more door 352 auto . It had a miss. never smoked spit out the carb sometimes. I paid $50 for it and everyone had worked on it.it had new cap rotor points condenser coil wires spark plugs . rebuilt carb and valve job. I was setting the points with a dwell meter and it had a steady jump. one lobe on the dist was worn down. changed the dist and it ran perfect. I took the dist apart . I finally decided some one had at some time filed the points with a aggressive file and damaged the hard outer part of the lobe and it wore down over time.
     
    Petejoe likes this.
  10. Petejoe
    Joined: Nov 27, 2002
    Posts: 9,954

    Petejoe
    ALLIANCE MEMBER
    from Zoar, Ohio

    That adapter just may allow me to run the engine and get whatever crap is causing it to loosen up.
    With the adapter I may be able to get it out and run it at 65 mph for an hour or so and see what happens. I've been guilty of babying it.
    By the way, no oil consumption on the engine. its a dry carbon and the anti fouler may not even work.
    Am running the hottest plug available.
     
    Last edited: Jul 11, 2019
    Old wolf likes this.
  11. rockable
    Joined: Dec 21, 2009
    Posts: 2,580

    rockable
    ALLIANCE MEMBER

    Check the valve clearance and do a compression check, as suggested, first. The problem is likely a lack of compression in that hole. The clearance adjustment may fix it. If not, you will have to at least pull the head.
     
    Petejoe likes this.
  12. Well did you find the trouble?
     
  13. Petejoe
    Joined: Nov 27, 2002
    Posts: 9,954

    Petejoe
    ALLIANCE MEMBER
    from Zoar, Ohio

    Realized the NGK plug numbers are hotter with the lower number.
    I Installed a hotter plug along with a non fouler and ran the truck all weekend without a miss. Going to drive it more yet before pulling the plug and distributor cap to inspect.
    With no fouling issues under these conditions, this points to a cylinder issue. Otherwise electronically it would still show a miss. I hopefully am going to get through driving season this way and tear it down this winter.
     
  14. Petejoe
    Joined: Nov 27, 2002
    Posts: 9,954

    Petejoe
    ALLIANCE MEMBER
    from Zoar, Ohio

    Quite a difference with that non fouler.

    [​IMG]

    Verses

    [​IMG]
     
    alanp561 and Old wolf like this.

Share This Page

Register now to get rid of these ads!

Archive

Copyright © 1995-2020 The Jalopy Journal: Steal our stuff, we'll kick your teeth in. Terms of Service. Privacy Policy.

Atomic Industry
Forum software by XenForo™ ©2010-2014 XenForo Ltd.