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Official spark plug thread: What do you run and why?

Discussion in 'The Hokey Ass Message Board' started by Buzznut, Aug 7, 2013.

  1. Buzznut
    Joined: May 9, 2008
    Posts: 2,349


    I'm trying to figure out what plugs would be best for my engine. I ran NGK XR45's and they fouled in less than 300 miles. Granted it's a '68 327 I'm at 10.3:1 compression, but the engine only has just under 2,500 miles on it and I shouldn't be having ring blow-by issues. I took a small butane torch to the plug electrodes and very little burnt off, so no excess/unburnt fuel. They seem to have soot on them and trace amounts of oil. I wonder if they aren't burning hot enough. I'm going to try Autolite 85's next.

    Not sure if we have a spark plug thread - this could be a good resource for all brands, models, applications. List yours here...
    Last edited: Aug 7, 2013
  2. Buzznut
    Joined: May 9, 2008
    Posts: 2,349


    Everyone running diesel engines? :D
  3. XR45 is designed for a very large gap - .060"

    Try the XR4 and run them at .030-.035"
  4. Autolite has always worked best for me.

  5. mustang6147
    Joined: Feb 26, 2010
    Posts: 1,847

    from Kent, Ohio

    Ford engines I run Autolite. They run the best. Clean ect....The engine feels better over 7500 rpms with high compression.

    Chevy SB I run Champions. No issue's

    BB chevy High compression Accell performed the best. Most passes without a fouled plug.
  6. gtowagon
    Joined: Mar 23, 2011
    Posts: 406


    Ac delco and I use 6 of them in my cammer
  7. fsae0607
    Joined: Apr 3, 2012
    Posts: 871


    Using Champions in my GMC. Good so far.

    Aw hell I'm not gonna lie... I like their logo! :D
  8. gimpyshotrods
    Joined: May 20, 2009
    Posts: 18,464


    Champions, 'cause that's what The Rebel used.
  9. I've used AC and Champion,,I'm happy with both. HRP
  10. scrap metal 48
    Joined: Sep 6, 2009
    Posts: 6,075

    scrap metal 48

  11. afaulk
    Joined: Jul 20, 2011
    Posts: 1,191


    Autolite racing plugs last much longer for me than NGK's.
  12. [​IMG]

    Champion 6-Com's, 7's, or Edison-Splitdorf 45's. Because they match the 'period' I'm aiming for best.
  13. Ones that Smokey Yunick designed.....
  14. Incorrect Heat Range
    APPEARANCE: The effects of high temperature on a spark plug are indicated by clean white, often blistered insulator. This can also be accompanied by excessive wear of the electrode, and the absence of deposits.

    CAUSE: Check for the correct spark plug heat range. A plug which is too hot for the engine can result in overheating. A car operated mostly at high speeds can require a colder plug. Also check ignition timing, cooling system level, fuel mixture and leaking intake manifold.

    RECOMMENDATION: If all ignition and engine adjustments are known to be correct, and no other malfunction exists, install spark plugs one heat range colder.

    Carbon Deposits
    APPEARANCE: Carbon fouling Is easily identified by the presence of dry, soft, black, sooty deposits.

    CAUSE: Changing the heat range can often lead to carbon fouling, as can prolonged slow, stop-and-start driving. If the heat range is correct, carbon fouling can be attributed to a rich fuel mixture, sticking choke, clogged air cleaner, worn breaker points, retarded timing or low compression. If only one or two plugs are carbon fouled, check for corroded or cracked wires on the affected plugs. Also look for cracks in the distributor cap between the towers of affected cylinders.

    RECOMMENDATION: After the problem is corrected, these plugs can be cleaned and reinstalled if not worn severely.
  15. Standard gas&oil
    Joined: Dec 3, 2010
    Posts: 289

    Standard gas&oil
    from USA #1

    It doesn't matter if your using AC Delco, Champion, Autolight, Jap plugs, ect. If your heat range is off and your tune is off they are going to foul.
  16. OT but
    I run autolite 605 in a slightly modified, stock boost.
    These are perfect if i it drive it easy, they are a little to hot to drive it hard for very long.
    Same series engine, different car.
    I run autolite 103 in a heavily modified, increased boost, and higher static compression.
    The 103s foul up if I drive it easy. Perfect if I'm driving it hard. It's tuned to run hard.
  17. Buzznut
    Joined: May 9, 2008
    Posts: 2,349


    It was running rich, but not for more than the first 20 to 40 miles, after that it was re-tuned and running great. What's weird is this: I ran it on a 180 mile trip...running it hard. It ran great, although at around 110mph the valves made noise, so I relashed them and problem gone. It still ran great. About 2 days later I pulled the carb to readjust a float that was too high. After putting the carb back on, it started running rough. It's not's as though the spark is being diffused. The roughness of the idle isn't in a pattern (as though it's one cylinder) instead it's erratic and pattern. I'm running a brand new Mallory Unilite...hoping the module, or whatever they call it, isn't the culprit. Bottom line, the erratic idle sounds electric/ignition related, not mechanical.
  18. I would be looking there, you pulled the carb, did some work on it, and put it back on and then it started running rough! Don't think that is a spark plug issue.
  19. S_Mazza
    Joined: Apr 27, 2011
    Posts: 363


    Vacuum advance distributor? Disturbed vacuum line while fixing carb? Just a thought.
  20. hoop98
    Joined: Jan 23, 2013
    Posts: 1,362

    from Texas

    Smokey sez:

    I spent a lot of time experimenting with various types of electrodes on spark plugs, spark plug gaps, diameter of center wire, center wire radiuses, center wire flat multi-ground electrodes, surface gap. flame ignition or plasma ignition. Various ceramics qualities in regard to dielectric strength, heat range, center wire sealing and the battle to remove all moisture in the center wire seal area. Remember I worked as a consultant twice for Champion spark plug. Matter of fact the first complete Champion plug lab with dyno was at my place 'bout in 1957 time frame and came back as a consultant again in the early '90s. So you could say I am half way qualified to talk spark plugs.

    I found small diameter center wire and a glass seal the best. The ceramic material formula and heat treat are very crucial to dielectric strength. Sharp edge flat center electrodes are the best, rounded electrode is very negative. More gap, say like .075 is best, but takes a very good ceramic with a no moisture center wire seal and a strong ignition in amperage and duration. This then puts plug wires in trouble reference leaking. As a rule no plug wire can handle it as good as a wire with added protection from a premium wire shield like Moroso blue. Seems like multiple ground electrodes are a little better, less misfire, especially late in race when oil control weakens. (This is not a power tool for round track racers.) This was durability medicine. I found we as a rule used too cold a plug.

    I think ceramic should be 'bout 1100°F for best ignition, the heat reduces the chance for misfire because of oiling or incorrect air fuel ratio. Plug gap should be all the sytem can stand reliably. I believe in individual coils for each cylinder with no plug wires. Here's a five cent tip on coil or condenser reliability: if either one gets so hot it burns when you touch them that engine will soon quit making noise. Remember it's harder to transmit electrical energy in elevated temperature without a significant loss of voltage also.

    Comparing a three foot plug wire to a one foot plug wire, about half the voltage is lost. Now this information is nowhere's near as critical to normal surface transportation engines as in state of the art racing engines. With a coil per cylinder we run without plug wires so I did the best I could. I plugged into spark plug surrounded with a heavy silicon boot for mechanical and dielectric strength and a sleeve which increased the dielectric strength of the wire. When we had to run plug wires.

    How 'bout platinum or other precious or exotic metals for spark plug electrodes? My experience is these expensive metals add life and durability, but for say a 500 mile Indy race they wouldn't be any advantage at all because all the race plugs are replaced every race. Where multiple electrodes are part of the design only one pair of electrodes will react, that being the pair (current and ground) that offer the least resistance, so multiple electrodes offer one advantage, optional electrical path in case of fouling of the normal or primary pair.

    The spark plug is now damn near 100 years old, and essentially the same since day one.
  21. Engine man
    Joined: Jan 30, 2011
    Posts: 3,476

    Engine man
    from Wisconsin

    I use AC in GM products and Autolite in Ford products. I believe in using OEM plugs. They built the engine and should know what plugs to use.

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