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Thread: HOW TO: Index Your Spark Plugs

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Posts: 21-30 of 61
2008-05-05 01:13:08
can't wait ,i'm anxious to find out what the outcome will be
2008-05-05 01:38:11
I'll post up some numbers when I get it all the variables straight
2008-05-17 00:03:11
whats the word?
2008-05-17 07:39:02
Right now my car is down, but I've been driving around with unindexed brand new BKR6E's. Getting the BHP reading and MPG readings. Then I will index them and get the readings etc.
2008-05-20 20:34:50
Car ran into some troubles, looks like I wont have any test results until I get it fixed... or a new motor goes in...
2008-05-29 03:31:38
Alright did some testing with this

Here is are my conditions:
  • 87 Octane Shell Gas
  • New NGK BKR6E Spark Plugs (Gapped by default at .032")
  • New OEM Spark Plug Wires
  • New OEM Distributor Cap and Rotor
  • '91 Intake Cam
  • 15* Timing
  • JWT Pop Charger/Stock Short Ram piping
  • SSAC Header 2.5"
  • 2.37" Catback with gutted Cat and Altima 2.5s Muffler
  • Sludge

How things are calculated:

Miles to the Gallon (MPG) - Miles driven divided by gallons fueled up.
Horsepower- I got these readings by the ScanGauge BHP (Break Horse Power or Flywheel Horse Power) Gauge.

Reading the Indexing - A mark with a Sharpie marker was put on top of the spark plug, so it would be visible from above. The mark is put where the ground electrode is located. More info about this can be found in the first post.

Not Indexed (Randomly placed)
I drove for 87 miles, about 60 highway miles (constant), 26 city miles. Redlining abotu 5 times. Fueled up 3.6 Gallons.


At 78* intake air (air going into the engine), the car made 178 BHP in at Redline.

Indexed 1 - The first indexing is by simply switching around spark plugs until they find the best position.

Due to the thread being different on all plugs, it is almost impossible to get a perfect index.

The Best Index that I could Make:
1st Cylinder: ~10 O'Clock
2nd Cylinder: ~6 O'Clock
3rd Cylinder: ~9 O"Clock
4th Cylinder: ~6 O'Clock

I drove for 97.5 miles, about 70 highway and 27 city miles. Redlining the car about 6 times. Fueled up 3.8 Gallons.

25.6 MPG

At 78* intake air (air going into the engine), the car made 189 BHP in at Redline.

Indexed 2 - After the next fuel up, I will index the spark plugs with the Morso Indexing Washers. In theory all of these should have a perfect 6 O'Clock Index.

I decided not to spend time on this, it requires time to replace all of the washers. I went onto trying the MPG's with the Bosch Platinum +2 Plugs.

Problem with our motors is that we can't have the spark plugs too low, if we do they will hit the pistons. So some washers would set the spark plug too low.

Have the spark plug too high is not good either, because it would keep the spark plug out of the cylinder. So in my opinion it is best to be able to index the spark plugs with the washers that they have on them, but with this method it will take a couple spark plugs before they perfectly fit on perfectly.

Just by doing a little simple index, it looks like I saw about a 10 BHP increase at the same intake air temperature
2008-05-29 08:13:49
subscribed i wanna see the results to this for sure. if i can gain 10hp just by putting my plugs in different im all for it.
2008-05-31 23:18:02
The above posted updated with MPG's and more information
2008-06-03 13:06:21
I indexed mine this past weekend after reading this with my new NGK plugs, it made a difference...at least in my gas mileage.
2008-06-03 13:41:39
Originally Posted by Nathan_Barstow
I indexed mine this past weekend after reading this with my new NGK plugs, it made a difference...at least in my gas mileage.

Since power gains are in BHP, thats nothing that you would feel, but in the long run it all adds up.

As for MPG gains, I'm very happy that it helped
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