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Thread: indexing plugs, hows, whys, and theory

  1. #1
    Blown 472
    Lets hear it, should I do it, what will I gain, and how would I do it on a 440 mopar and 460 ford.

  2. #2
    Indexing plugs is mostly for high compression motors. You don't want the electrode in the way of the piston. Bad things will happen.
    It also controls the way the flame travels in the combustion chamber.
    Pain in the ass to do. You need different thickness washers so you can setup where the electrode is when the spark plug tightens up.

  3. #3
    Here's what I know and found on the net.....
    Indexing refers to an old racer's trick whereby the spark plugs are installed so that the ground electrode is oriented to face the intake valve (usually) in an effort to "open up" the spark to the incoming air/fuel charge. This is accomplished by placing a washer underneath the spark plug's shoulder area (of a specified thickness) so that after properly torqueing the spark plug, the electrode would be pointed in the desired direction, usually towards the incoming air/fuel charge from the intake valve.
    Some racers have discovered that certain engine configurations made more power with the spark plug pointed away from the air fuel mixture.
    It is important to note that any power increase will be small, typically 1-2% of total engine output, and the proper indexing orientation can only be discovered after extensive engine dyno testing.
    Indexing is a waste of time for racers that do not have the training or the dyno facilities to document the results of their efforts. However, professional race teams racing in classes that have strict engine specifications can gain a slight edge over their competitors when spark plugs are indexed for optimum performance, provided they have performed adequate dyno testing.

  4. #4
    Blown 472
    The reason I ask is if the ground strap where facing the chamber and was for what ever reason hot could it produce preignition?

  5. #5
    Yes! If you are blown,nitroused,or high compression you probably want to use a non-projected nose plug. This is so the ground strap is shorter and cooler, you also can shorten the ground strap, cut it so it stops just barely over the center electrode. This makes it have less length overall so it runs cooler. Any of the "funny plugs" (the ones with the U groove,split ends,etc)will promote preignition more than a normal plug too. Indexing the plug in a domed piston motor enhances the flame front in the direction that you want it to go. The 2,3,or 4 side electrode squirrel plugs shroud the spark/ flame front and slow the burn. If you run faster with those, retard the timing a few degrees and use a normal plug. Electricity takes the path of least resistance so at any time only 1 spark is made from 1 electrode. The other electrodes are just in the way. Airplane engines use multiple electrodes but the plugs are usually only checked during the annual inspection. They want reliability and the engines usually only turn 2000 RPM or so. There you have it! TIMINATOR

  6. #6
    I have to index mine to keep the ground strap from hitting the piston.It is a bitch and it does get old.

  7. #7
    Originally posted by 565edge
    I have to index mine to keep the ground strap from hitting the piston.It is a bitch and it does get old.
    That seems like the only good reason to bother. Can't imagine that the position of the ground strap would affect flame travel in a measurable manner.
    But, hey, there's always something to do with the motor, right?

  8. #8
    Blown 472
    So I want the open part of the plug facing the intake valve and the curved part of the ground strap facing away from the intake?? and get side gapped plugs too?

  9. #9
    Ground strap (where it fastens to base) 11:00 to 1:00.

  10. #10
    Blown 472
    Originally posted by Fiat48
    Ground strap (where it fastens to base) 11:00 to 1:00.
    For both the ford and mopar??

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