indexing of plugs does have a certain advantage! but ya have a slight
problem with the shimming operation! why-o-why you ask? here's the rub!
you have a properly ported head. then you CC the combustion chamber
...right? so you now have a balanced compression ratio in each cylinder
(if yer crank is properly indexed!)...right? then you go out and grab 4
plugs, put a index mark on them and begin screwing them in to find you are
near 180 degrees out of sync for indexing. so you decide to use the copper
shim method to get it to index....right? WRONG! you just blew your CC'ing
of the combustion chamber! you go out and buy a whole box of new plugs and
begin trying the plugs from 1 cylinder to another untill you come up with a
set that are darn close to perfect or dead on! use as little a shim as
possible in order to preserve the combustion chamber's originally designed
volume. now! this is one of the last steps in achieving a balanced burn
in all the cylinders in a blueprinted engine! what are you gaining? not a
lot in a street aplication. but in a race situation it's possibly the
tinyist advantage between winning and loosing! actual dyno results? i
could not remember. but always index a spare set at the shop, mark wich
cylinder each plug fits into before heading to the track! the last thing
you want to do is fool with finite stuff like that at the track! a set or
two pre gapped and ready for installation will be a great help if done in
advance!
chuck
been there.....broke that..... :)
-----Original Message-----
From Ron Soave <soavero at yahoo.com>
To: spridgets@autox.team.net <spridgets@autox.team.net>
Date: Monday, August 04, 2003 10:23 PM
Subject: Fun with sparkplugs
>Too much time on my hands. The racecar is ready for
>the upcoming VCSDA event at Grattan Raceway and I have
>been tinkering with little stuff (like making the diff
>leak free in the off chance that there is actually
>someone behind me at some point in the race). Anyway,
>at high RPM, I had a plug gap close to .010 from a
>piston being used as a gapping tool. So I switched to
>non-protruding tip NGKs, and have shimmed and indexed
>the plugs (found a ton of "just right" .006" to .040"
>shims at work in the scrap bin). Question is (and
>this is pretty esoteric), have any of you guys dyno'd
>a car and seen any measurable improvement from proper
>indexing of plugs? Not covered in Vizard or Stapleton
>so I assume the improvement is trivial, but it's a
>favorite trick of dragster car and bike guys.
>
>11 Days Til Green Flag,
>Ron
>"Grasshopper"
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