Indexing Sparkplugs
Thread Starter
Burning Brakes
Joined: Apr 2000
Posts: 1,012
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From: Minnesota
Indexing Sparkplugs
Anybody heard of indexing sparkplugs? So the electrode won't have a chance to hit the top of the piston
Was outside doing some yardwork--took a little water break--turned on the tube and Two Guys Garage was talking about this--didn't catch the whole thing--did I hear right or did I get something out of context?
SEMPER FI--1970 Dave
Was outside doing some yardwork--took a little water break--turned on the tube and Two Guys Garage was talking about this--didn't catch the whole thing--did I hear right or did I get something out of context?
SEMPER FI--1970 Dave
Melting Slicks
Joined: Nov 2001
Posts: 2,668
Likes: 43
From: Eastern US XX
Originally Posted by 1970 Dave
Anybody heard of indexing sparkplugs? So the electrode won't have a chance to hit the top of the piston
Was outside doing some yardwork--took a little water break--turned on the tube and Two Guys Garage was talking about this--didn't catch the whole thing--did I hear right or did I get something out of context?
SEMPER FI--1970 Dave
Was outside doing some yardwork--took a little water break--turned on the tube and Two Guys Garage was talking about this--didn't catch the whole thing--did I hear right or did I get something out of context?
SEMPER FI--1970 Dave
Team Owner
Joined: Sep 2001
Posts: 30,958
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From: Middletown Connecticut
Cruise-In IV Veteran
got em on my lt-1, a trick my father taught me 
only problem is, you need to buy more then 8 because threads are always random...
random threads = random electrodes
only problem is, you need to buy more then 8 because threads are always random...
random threads = random electrodes
Thread Starter
Burning Brakes
Joined: Apr 2000
Posts: 1,012
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From: Minnesota
Originally Posted by 1ARACE
details please...i've never heard of this before..what do you do and how does it work?
SEMPER FI--1970 Dave
Le Mans Master
Joined: Jan 2006
Posts: 9,192
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From: Boca Raton Florida
This a technique you use to make sure the Electrode is at the top of the plug hole. Mark the plug on the side that the electrode is on with a sharpie and install it, check for correct torque with the mark to the top, if it is not you can install those little aluminum crush washers to get the plug positioned in the hole so that the mark is at the top with correct torque
Melting Slicks
Joined: Nov 2001
Posts: 2,668
Likes: 43
From: Eastern US XX
Originally Posted by 1970 Dave
Ditto--is it a method of putting the plugs in or an aftermarket gizzmo?
SEMPER FI--1970 Dave
SEMPER FI--1970 Dave
In a nutshell, you you mark the outside of the plug where the electrode is attached to the shell. The goal then is to install the plugs with the mark set so the electrode is the furthest distance from the piston. As someone previously mentioned, you generally need to start with more than 8 plugs if you don't use "indexing washers" (i.e. tapered seats don't have washers), then you find a hole where a particular plug "indexes" correctly, then do the same with the next plug and so on until you fill all the holes!!
!!! Sixfooter beat me! Same-same....
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Le Mans Master
Joined: Jun 2002
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From: I can walk to MA
I think the domed piston is the culprit. A lame low compression
engine can be woken up with installation of domed pistons.
If running a "hot" plug - the clearance is even less.
How do you KNOW if you need indexing ? When you pull the plugs
to change them (running poorly - 7cyl), and one of the plug electrodes
is bend over and touching the center electrode. The gasoline mixture
didn't do that. High compression didn't do that .... the top of the piston did.
engine can be woken up with installation of domed pistons.
If running a "hot" plug - the clearance is even less.
How do you KNOW if you need indexing ? When you pull the plugs
to change them (running poorly - 7cyl), and one of the plug electrodes
is bend over and touching the center electrode. The gasoline mixture
didn't do that. High compression didn't do that .... the top of the piston did.
Le Mans Master
Joined: Jan 2006
Posts: 9,192
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From: Boca Raton Florida
Well, sounds like that one needed it. The determination really needs to be made before you put the heads on.Back in the day it was supposed to give you a little more edge, more efecient burn or some such, I did it and immediately imagined a .2 sec improvement in 1/4
Race Director
Joined: Aug 2004
Posts: 10,628
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From: Duvall, WA
Quite a while ago (10-15 years) one of the car magazines (Hot Rod?)dynoed an engine with indexde vs. non-indexed spark plugs and came to the conclusion that with the typical normally aspirated engine it made no difference whatsoever. Doesn't hurt anything to do it, though. Plus when your neighbor starts bragging about his new geriatric-mobile Cadillac CTS-V, you can include "indexed spark plugs" when you start listing your Corvette's engine specs.
Last edited by rcread; Apr 10, 2006 at 06:40 PM.
Racer
Joined: Jan 2005
Posts: 499
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From: Enfield CT
I thought when you index a spark plug you are positioning the open part of the electrode to face the valves so that the spark can better ignite the fuel. I have read that this is good for a couple of extra ponnies!!!
Last edited by bozzman3; Apr 16, 2006 at 06:24 PM.
Drifting
Joined: Nov 2005
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Originally Posted by bozzman3
I thought when you index a spark plug you are positioning the open part of the electrode to face the valves so that the spark can better ignite the fuel. I have read that this is good for a couple of extra ponnies!!!
exacty what i was always told,that ultimately you wantedthe gap side pointed towards the intake valve for a cleaner burn.
Race Director
Joined: Nov 2002
Posts: 12,142
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From: Taylor Michigan
Use R45 plugs
All of that so called indexing of plugs is a waste of time. All you really need to do if it`s a high compression engine, is to buy the correct plugs without the extended tip. R45`s would be correct for most engines. A R45S is incorrect. The reason I suggest the R45 is that it`s the only alternative besides a R43 which may be too cold and prone to carbon up. As you all have probably found out, the #44 plug is no longer available. Those dumb parts store jockeys will sell you a "S" series plug every time, and it will be wrong every time if it`s 11-1 or over. The dome of the piston may hit the extended electrode. Champion plugs with the "Y" sufix is incorrect also as it has the same extended electrod tip as the AC R45S`s. So beware if you have a SB chevy with high compression and factory style heads.
Melting Slicks
Joined: May 2005
Posts: 2,486
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From: Elkhart Lake, Wisconsin
We index the plugs in our race motors for performance / better burn. The idea is to have the electrodes aimed towards the area of highest squish. We have dynoed several different motor types over the years and it does make a small difference maybe 1%, but when you are talking race cars that all use the identical motors you look for every HP.
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Burning Brakes
Joined: Oct 2003
Posts: 836
Likes: 26
From: Harrisburg Pa
Originally Posted by NHvette
When you pull the plugs
to change them (running poorly - 7cyl), and one of the plug electrodes
is bend over and touching the center electrode. The gasoline mixture
didn't do that. High compression didn't do that .... the top of the piston did.
to change them (running poorly - 7cyl), and one of the plug electrodes
is bend over and touching the center electrode. The gasoline mixture
didn't do that. High compression didn't do that .... the top of the piston did.