Indexing plugs ??

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superdart

superdart

Shade Tree Tinker Gnome.....
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I have read and heard about indexing the plugs on motors. Is it worth it? What is the best meathod? Shims?

I figure if the power gain is worth it, I might as well do it, since it's a pretty cheap mod.
 
Depending on the motor and its condition its worth about .03-.05 tenths of a second on the strip.It does work and if you have a well tuned ear,you will hear a difference in the starting and running of the motor,Mrmopartech
 
Moroso sells flat copper washers of different thickness for indexing the plugs. They also sell a little round flat piece with a sparkplug thread in the middle. The idea is to mark your plugs before you take them out so you know where the top is and screw them one at atime into this doohickey. make a line where the line on the plug is and number it the same as the cylinder it came out of. This will make future plug changes easier to index.

don
 
WOW, that's a more significant impact than I expected.

It's a 9:1, .030 over 360 with a dual pattern 455/475 cam, and the usual list of good mods (FBO ignition, intake, 4 barrel, electric fuel pump). The motor has less than 1500 miles on it.

Guess Summit or Jegs has the index tool and spacers......(time to go shopping).
 
OK, new stupid question (and I'm too lazy to do search the net right now).

I always "assumed" that plugs would be indexed so the spark would face down into the cylinder, where the A/F mixture is coming up at it.

But now I have been told I want the spark to face UP into the valves.

A) Is this correct?
B) Should it be facing a particular valve? Intake? Exhaust?
 
The spark plug gap opening should face the exh valve. Indexing does have definate positive effects. How much depends on how bad they are now really. Yhe guys that showed me just drew a small line on the ceramic in line witht he gap, and then threaded them in the heads to see where they would stop. Then adjust with shims. There is also a benefit to side gapping plugs...But they are not great fro street driving, so I'd do a "track only" set.
 
superdart said:
WOW, that's a more significant impact than I expected.

It's a 9:1, .030 over 360 with a dual pattern 455/475 cam, and the usual list of good mods (FBO ignition, intake, 4 barrel, electric fuel pump). The motor has less than 1500 miles on it.

Guess Summit or Jegs has the index tool and spacers......(time to go shopping).
Click to expand...


You realize he did say .03 - .05 tenths. in other words 3/100ths - 5/100ths of a second. Not 3/10ths or 5/10ths. just checking. :toothy7:

Anyway, im curious to see your improvements. :thumbup:
 
Plus chamber design and head material will have an affect on it. Closed chamber heads don't benefit near as much as open chamber heads do.
 
Technically he said ".03 -.05 TENTHS" which is actually 3/100ths of a tenth, which is only .003 to .005...which is REALLY unimpressive, but I knew what he meant :) But thanks for pointing that out:thumbup:

I figured ANY gain for a measly $14 is good. I was expecting people to tell me not to waste the time....

..then again, this is all moot, since the car has never seen the strip.:sad:
 
I dont waste my time...lol. But I know many racers who do. In one case, it's his "secret weapon" when he has to run a hair better..lol. There is definately a positive result as far as power goes.
 
If you are bracket racing the gain won't matter. The only reason you would want to squeeze every bit out of your performance is if you are running stock eliminator or super stock. In other words if you are running heads up and you need a little more to beat the other guy.

Chuck
 
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