Plug Indexing

Maybe a dumb question............

Is spark plug gap indexing at all relevant in a blown alcohol motor?

Or just a waste of effort?

This is for a very hot street deal. I have 3 plugs per chamber.

Once in awhile I will pull the center plugs out to examine them. The other two will remain in place full time.

The peripheral plugs (outer two) will be indexed because they are proximally close to the edges of the combustion chamber/bore. Obvious shrouding concerns.

The center plugs I am not so sure about though.

NGK 6061 plugs.

Thanks.

 

You sure get into some stuff. I know that the big show cars stagger the gap to the center of the cylinder so they would be facing each other and the ground strap would be facing the liner if that makes sense. They say the parts look nicer, not really a performance advantage. The original reason for plug indexing was to clear the dome in non Hemi situations, so that it didn’t whack the ground strap and close the gap off. I can’t think of anyone that I’ve ever seen or talked to that seen a performance advantage by solely changing the indexing of the spark plug, that includes some wankel rotary stuff that consisted of a leading and trailing ignition. I know some of the early KB olds stuff had dual plugs in top alcohol in the old dual super mag III days.

Id like to see that chamber. Are you staggering the timing per plug or anything fancy?

 

Spark will be simultaneous single fire (meaning all fire at once).

Send me your email Rob. I have no clue how to post a picture here at ITA.

1500 mj's per plug times three.

 

I sent you a private message.

 

Sent you a pic...........

 

Thanks for the heads up it got caught in my spam filter. Happen to have any pics of the piston? What heat range? You could aim the two outers towards each other and then put a “polar gap” plug in the center with no electrode.

 

Heat range to be determined.

Yes the two peripheral plug gaps will end up facing each other from the opposing sides of the 4.500" bore.

The central plug, I have not yet made up my mind about.

The piston crown is a flat-top with 4 very tiny valve reliefs. Nothing fancy and nothing in the way. The combustion/conversion space is all in the head. No impedances in the way.

Thermal barrier coatings.

The goal is to reduce the negative work done against the crank to zero. Initial testing will be with boosted meth. Nitro added down the road..

The two outer plugs will exist in place long term. I will pull the center plugs with some regularity to inspect.