Spark Plug Heat Range Question
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Spark Plug Heat Range Question

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    Senior Member sanger448's Avatar
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    Default Spark Plug Heat Range Question

    I am running Autolite AR13 plugs with my MSD 6al Box. I know the motor is running rich at low speeds and have never checked plugs after a full throttle run. Having a miss above 2500 rpm and thinking of trying next step hotter plug to help burn off excess fuel.(90% of my driving is in the 2500-3000 range) Trying to figure out next hotter heat range to use. Here's a photo of what my plugs look..

    Engine: 427 + .060, 12.5:1, running tunnel with two Holley 650HP series. Don't know the jets installed at this point.
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    steelcomp was here
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    Quote Originally Posted by sanger448 View Post
    I am running Autolite AR13 plugs with my MSD 6al Box. I know the motor is running rich at low speeds and have never checked plugs after a full throttle run. Having a miss above 2500 rpm and thinking of trying next step hotter plug to help burn off excess fuel.(90% of my driving is in the 2500-3000 range) Trying to figure out next hotter heat range to use. Here's a photo of what my plugs look..

    Engine: 427 + .060, 12.5:1, running tunnel with two Holley 650HP series. Don't know the jets installed at this point.
    That plug is plenty hot for what you're doing. You need to fix your fuel issue and check your timing.
    If God is your co-pilot, change seats!
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    Senior Member sanger448's Avatar
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    The timing if set for 36 degrees at 3000.

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    steelcomp was here
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    Quote Originally Posted by sanger448 View Post
    The timing if set for 36 degrees at 3000.
    If you're running around at 2500rpm, what is it then? IMO you don't need a timing curve and should just lock it in at 36 (if that's where the engine is happy). I know that's another subject, but may be relative.
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    Senior Member sanger448's Avatar
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    I think if was close to 28 degrees at 2500. IF I was to change jet size any suggestions on how many sizes to drop to lean out mixture some.

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    Senior Member EVILFORCE's Avatar
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    Looks like you need both. Jet change and heat range change. If I remember the AR 13 is a pretty hot plug. From the looks of the soot on plugs I would reduce the fuel. LOTS.
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    Senior Member sanger448's Avatar
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    Quote Originally Posted by EVILFORCE View Post
    Looks like you need both. Jet change and heat range change. If I remember the AR 13 is a pretty hot plug. From the looks of the soot on plugs I would reduce the fuel. LOTS.
    That's what I was trying to figure out... if it would be safe to set up to the next hot plug without burning anything up.

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    gn7
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    Quote Originally Posted by sanger448 View Post
    I think if was close to 28 degrees at 2500. IF I was to change jet size any suggestions on how many sizes to drop
    Quote Originally Posted by sanger448 View Post
    That's what I was trying to figure out... if it would be safe to set up to the next hot plug without burning anything up.
    Is it me, or do you think you can make that plug look beter by making it hotter. Are you under some belief that if the plug is hotter it will burn the excess fuel?

    As for the timing. You THINK its 28, but you don't know. What do you THINK the timing is on you daily driver on the freeway at 2200 Rs. Think its 28?

    I cannot imagine the plugs looking like that with 2 650 HPs that are jetted stock, and have their floats adjusted correctly. Just doesn't seem possible.
    Also, what plug wires are you running.
    What type of timing cover is on the motor?
    Have you ever verified TDC on the damper against the timing tab?



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    Senior Member sanger448's Avatar
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    Quote Originally Posted by sanger448 View Post
    I think if was close to 28 degrees at 2500. IF I was to change jet size any suggestions on how many sizes to drop to lean out mixture some.
    Just checked and found out that the jets are 70's unless the previous owner changed them out.

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    gn7
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    Quote Originally Posted by sanger448 View Post
    Just checked and found out that the jets are 70's unless the previous owner changed them out.
    You're too funny. You THINK the timing is 28 at 2500, and you THINK the jets are 70s, unless of course the previous owner changed them out

    So you go to the doctor for a little "troubleshooting" and you tell him you THINK you head hurts, and you THINK you may have drank a little too much the night before.

    I'd tell you what I THINK, but is get banned from the sight!



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    I am trying to eliminate an engine miss at 2500+. Thought this excess carbon deposit might allow for the plug to ground out along insulator to block. This picture is not my plug but mine looks very similar to it. Solid black. Some deposits on thread.

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    gn7
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    Quote Originally Posted by sanger448 View Post
    I am trying to eliminate an engine miss at 2500+. Thought this excess carbon deposit might allow for the plug to ground out along insulator to block. This picture is not my plug but mine looks very similar to it. Solid black. Some deposits on thread.
    Now your asking for info by proxy.
    I'm done



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    Quote Originally Posted by gn7 View Post
    Now your asking for info by proxy.
    I'm done
    Bob. Be nice.
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    steelcomp was here
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    Quote Originally Posted by EVILFORCE View Post
    Looks like you need both. Jet change and heat range change. If I remember the AR 13 is a pretty hot plug. From the looks of the soot on plugs I would reduce the fuel. LOTS.
    So what do you think a hotter plug is going to accomplish? FYI this plug is equiv. to a 6 range NGK.
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