Which Way Is Right For Your Spark Plug Thumb Nuts?


Does the clip go in the Center of the Thumb Nut?

Today we have one of those questions that may not have a correct answer. Oh on the surface it may seem simple. But you will see the logic in what you may think is wrong? Or is it right? Like the famous Gold or Blue Dress. I suppose its all in how you want it to be.

OR? Clamped under the thumb nut?

The design of the thumb nut allows easy slip on and off of the wire clip. Or is it too loose?

Sure makes a Sparkplug look bad ass!

Just pull off your new nut. OUCH! That sounds painful. Oh hell, there is an entire story on it.

We did a Story on Brass Nuts A ways Back if you want to know more. CLICK HERE

14 replies
  1. Tuobanur
    Tuobanur says:

    It seems to me that is something that you would always want to stay put, with that said I say it should always be clamped under the nut.
    It is shaped the way it is shaped to allow you to get a good grip on the nurl to tighten it.

  2. Bilge Rat
    Bilge Rat says:

    They are badass because you have to be badass to work on a running 6 cylinder with bare spark plug terminals. I’ve been zapped too many times by exposed terminals so it’s nice orange boots for my plugs.

  3. Darthtrader
    Darthtrader says:

    Logic says that if the designers had wanted the nut to be tightened onto the terminal, it would have been a round eyelet as opposed to a clip-on terminal.

  4. Brian Robinson
    Brian Robinson says:

    A small ring end actually looks more original than these oversized fork ends (bare and crimped with a specific Rajah crimper.) Also original spark plug bases were black oxide vs. cad.

  5. Mark in da U P
    Mark in da U P says:

    Clamp em down, do you want them to come off in rough water. Iv’e seen round terminals that you had to put under the thumb nut. However I don’t know if they were original. Like Bilge Rat I have been zapped by a spark plug wire or two. It makes you more careful.

  6. Chad
    Chad says:

    It’s been I while since we’ve talked wires, plugs and terminals. I went a little overboard with the research back when I was restoring my ’52 Sportsman. I can only speak for early 50’s era boats. CC used a Rajah split ring terminal that was screwed under the nut. Also, from the photos that I dug up, they often used an aluminum nut. And the Champion plugs from the era were black. None of this really matters as I have never received a point deduction for a brass nut or a rubber booted terminal. I guess it all depends on the show or the judge on that given day.

    In the end, it really doesn’t matter as long as they’re securely attached. And if you don’t care about a point deduction, go with rubber boots. Getting zapped by a thumb screw will wake you up quick.

  7. Troy in ANE
    Troy in ANE says:

    Since we have been talking about exploding boats, fume detection, and other means of making our boats safer I would like to point out that IMHO clipping the ignition wire in the center of the thumb nut is leaving way too much room for a loose fit and thus an open spark that could create the very problem we are all trying to avoid.

  8. don danenberg
    don danenberg says:

    Listen to Chad,
    He did his research correctly!

    Rajah, split-ring, (acting as a lock-washer) as in the center of his first photo, the ALUMINUM turn-nut above it tightening it down, NO Brass, NO rubber boots.

    You really need to hear from Jim Staib and Joe Morrison.
    Joe provided me with NOS (New Old Stock) wires with Rajah split-ring ends for #48510 (KA) but did not have full lengths for #48908 (M), but Jim Staib did have reproductions of 7-mil black wires with Rajah Split-ring ends for that.

    I have many photos, but haven’t been able to post such here for years?

    Joe…, Jim…,????

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