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    Results 1 to 6 of 6
    1. #1
      Join Date
      May 2014
      Location
      Louisville, KY
      Posts
      57
      Country Flag: United States

      One clean spark plug

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      I started up my new engine recently and have been working through several issues. Getting timing set, rough idle, swapping from FI controlled timing back to mechanical advance, chasing a couple oil leaks, adjusting valves, etc.

      I pulled the plugs so I could spin the motor to confirm TDC and found one plug clean. Have you seen this before? I’m assuming this meant that cylinder wasn’t firing.

      How do I find the problem. I ordered new plugs and am waiting for them to come in. I megged the plug wires, they seemed good.

      I checked the distributor cap, the cap and posts and rotor seemed ok.

      Scratching my head and looking for suggestions.

    2. #2
      Join Date
      Apr 2001
      Location
      The City of Fountains
      Posts
      15,971
      Country Flag: United States
      How about sharing what engine this is? What ignition system? Details!

      Andrew
      1970 GTO Version 3.0
      1967 Cougar build
      GM High-Tech Performance feature
      My YouTube Channel Please Subscribe!
      Instagram @projectgattago
      Dr. EFI
      I deliver what EFI promises.
      Remote Holley EFI tuning.
      Please get in touch if I can be of service.

      "You were the gun, your voice was the trigger, your bravery was the barrel, your eyes were the bullets." ~ Her

    3. #3
      Join Date
      May 2014
      Location
      Louisville, KY
      Posts
      57
      Country Flag: United States
      It’s a 406 SBC. Recently rebuilt. Aluminum, angle plug heads (pro top line 220 heads). Eagle rotating assembly with flat top hypereutectic pistons, approx 10.5:1. (Block was zero decked and heads were milled). Comp roller cam and roller rockers. Air gap rpm intake. Small cap HEI System with e-core coil.

    4. #4
      Join Date
      Apr 2001
      Location
      The City of Fountains
      Posts
      15,971
      Country Flag: United States
      I'd start with the basics. Was the plug wire attached securely to the distributor? Was it secure to the spark plugs? Check the distributor cap. Is the post for that cylinder ok? Is the rotor good? Is there a break in the spark plugs wire...do a resistance test.

      Andrew
      1970 GTO Version 3.0
      1967 Cougar build
      GM High-Tech Performance feature
      My YouTube Channel Please Subscribe!
      Instagram @projectgattago
      Dr. EFI
      I deliver what EFI promises.
      Remote Holley EFI tuning.
      Please get in touch if I can be of service.

      "You were the gun, your voice was the trigger, your bravery was the barrel, your eyes were the bullets." ~ Her

    5. #5
      Join Date
      May 2014
      Location
      Louisville, KY
      Posts
      57
      Country Flag: United States
      Cap and rotor are new, they look good. Posts are solid. I did a resistance check of the plug wires, they are good. It may have been a connection problem, but I wasn’t paying close attention when I removed the plug wires. They will be securely connected when reinstalled.

    6. #6
      Join Date
      Oct 2014
      Location
      DFW, Texas
      Posts
      422
      Country Flag: United States
      You can take a spare plug, ground the threads and run the motor to verify spark on that cylinder.

      If you have spark, I'd guess the intake valve isn't opening. Pushrod bent, pushrod misaligned, broken rocker, etc.

      1972 Plymouth 'Cuda - Not LS-swapped, 5.7L Hemi [MS3 Gold Box], T56 Magnum 6-speed - 'Cuda Build Page
      1976 Dodge D100 - Warlock
      2016 Subaru WRX - E30 Tune






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