You cannot use any reading that you saw on your plugs after a race as any basis
for changes. Your plugs can change in such a quick time that without a dyno
your readings will mean almost nothing. The correct way to read plugs at a
track if you have to is to make a few laps and then accelerate hard out on a
lap and on the last corner and shut the engine down when you let off to coast
into the pit lane to do your readings. Running your engine any amount of time
between full load on your engine and your reading will give you false readings.
Your racing engine requires such small adjustments and tolerances than what
?reading plugs? is intended for with street cars that using this method is not
very useful compared to other methods such as a proper gas analyzer.
I will add that using a dyno logging air fuel ratio you can also view how the
profile of your needle is working and adjust needles only where needed based on
piston heights instead of basing your needle choices on overall lean/richness.
-Steve
> On Jun 28, 2017, at 10:32 PM, Henry Morrison via Fot <fot at autox.team.net>
> wrote:
>
> Thanks for your replies. I usually check my plugs in the reflection in my
> knockoffs from the light from a Coleman lantern. My current needle supplier
> has not suggested anything other than the RH, usually he has a plethora of
> suggestions.
>
> I didn't build the engine but it has an advertised compression ratio north of
> 10:1. It has an Isky cam with the number at home in the file. Previous
> owner ran an couple of races at altitude (+- 5000 ft.) and one Kastner Cup
> down at about 800
> ft..................................................................................................................................................................................with
> the SM needles.
>
> I plopped the RH needles in at Blackhawk and it still looked lean. Hopefully
> I haven't done any damage.
>
> Bruce pulled well up above 5000 revs, I didn't dare venture up to 6000, but
> he felt like he would go there no problem.
>
> I'll be at Road America with at least as many needles as spare
> spokes......................
>
> Cheers, Henry Morrison, Albuquerque, NM
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