Indexing plugs - Harley Davidson Forums: Harley Davidson Motorcycle Forum
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post #1 of 13 (permalink) Old 01-03-2013, 04:27 PM Thread Starter
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Indexing plugs

trying to get a good opinion on the best way to index plugs, and if it really prooves any gains

some say open the spark up to the intake, others say exhaust, and some say it depends on the shape of the combustion chamber as to what way you want to expose the spark

just curious on peoples thoughts and experiences

98 Evo 83.5ci, custom cam, 44cv, lightened ballanced crank, H-Beam rods, beehive springs, tapered pushrods, johnson hylift lifters, SE slip-ons no baffle, 101.78 hp @ 6200rpm
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post #2 of 13 (permalink) Old 01-03-2013, 06:16 PM
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NHRA Stock engine builder in our area says there is no measurable difference on his dyno and he will do about anything for horsepower. Couple of current class records to back up his knowledge.


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post #3 of 13 (permalink) Old 01-03-2013, 06:37 PM
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Waste of time. Finding the best heat range would seve you better regarding results.

I know guys that changed spark plugs between each round, bracket racing, when I was younger. A friend of mine ran the same set from the year we graduated highschool, well into 5 years past that. He ran consistant 11:80's. (68 Chevy Malibu 396 BB)

Not saying plugs aren't important, but to spend time indexing plugs on a street ridden machine is a waste of time. You'd be better off spending time reducing weight, and seeing and feeling more results.

You're trying to make a 700+ bike be fast. Shave weight. Asian bikes that have 150 HPs are sub-400 lbs for a reason.

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post #4 of 13 (permalink) Old 01-03-2013, 09:24 PM Thread Starter
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my bike is only 750 or so with me on it, not sure how much more weight i can save without taking mirrors and front signals off

well now we know about the plug situation, i suppose i will just make sure i have a fresh properly gapped plug for the dyno n run with that

98 Evo 83.5ci, custom cam, 44cv, lightened ballanced crank, H-Beam rods, beehive springs, tapered pushrods, johnson hylift lifters, SE slip-ons no baffle, 101.78 hp @ 6200rpm
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post #5 of 13 (permalink) Old 01-03-2013, 09:48 PM
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Quote:
Originally Posted by Dave63 View Post
Waste of time. Finding the best heat range would seve you better regarding results.

I know guys that changed spark plugs between each round, bracket racing, when I was younger. A friend of mine ran the same set from the year we graduated highschool, well into 5 years past that. He ran consistant 11:80's. (68 Chevy Malibu 396 BB)

Not saying plugs aren't important, but to spend time indexing plugs on a street ridden machine is a waste of time. You'd be better off spending time reducing weight, and seeing and feeling more results.

You're trying to make a 700+ bike be fast. Shave weight. Asian bikes that have 150 HPs are sub-400 lbs for a reason.
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post #6 of 13 (permalink) Old 01-03-2013, 11:42 PM
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Quote:
Originally Posted by 98DARKHORSE View Post
my bike is only 750 or so with me on it, not sure how much more weight i can save without taking mirrors and front signals off

well now we know about the plug situation, i suppose i will just make sure i have a fresh properly gapped plug for the dyno n run with that
It depends on how serious you are about the weight loss.

Fiberglass fenders.

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Ti pipes. Expensive, but 1/3rd the weight.

Aluminum fender struts.

Depending on your own weight, most guys could stand to lose an easy 15-20 lbs, that would be more difficult to shave off the bike, then diet and exercise. Not saying YOU need it, just making a point that most people, myself included, could lose weight, and that costs NOTHING.

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post #7 of 13 (permalink) Old 01-04-2013, 05:36 AM
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Indexing plugs never has shown us anything here.
We would not let the ground strap face the chamber, but other than that, proper gap, and heat range and your good to go.
FWIW, our 108" AHDRA Mod Bike was 577 lbs. wet, with the rider suited up........
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post #8 of 13 (permalink) Old 01-04-2013, 06:39 AM
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we quit doing it on our drag bikes years ago,dont bother.best wieght savings you can do is rotating wieght,wheels & rotors.taking 1 pound of rotating wieght is like taking 7 pounds off the bike

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post #9 of 13 (permalink) Old 01-04-2013, 09:39 AM
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Yes.
The PM front wheel on our bike w/o bearings/tire, weighed 6.6 lbs if I remember correctly.

When we went from an old steel Bandit clutch basket to an aluminum one, and I manufactured the drive dogs,(with spares) from 7075-T6 for that also.
Made a difference.
Scott

"....3 dueces and a 4 speed..........and a 389"..........
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post #10 of 13 (permalink) Old 01-04-2013, 03:18 PM Thread Starter
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good info guys thanks

oh and im 5'6 120 lbs lol if anything i should add a few pounds im more looking to get the most power from my motor while keeping it on the street and without making it bigger lol in all reality i just want the 100hp mark

98 Evo 83.5ci, custom cam, 44cv, lightened ballanced crank, H-Beam rods, beehive springs, tapered pushrods, johnson hylift lifters, SE slip-ons no baffle, 101.78 hp @ 6200rpm
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