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Heres a silly question - does it matter if you do a shut down run right before reading the plugs if you're looking at the ground strap for a timing indicator?

If not then I would say it has more to do with the timing and not the effects of changing the timing (i.e. EGT)

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Its much easier to read a true reading on a shut down
run.. its more pronounced

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Will it usually stay in the same spot though?

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From what I have seen .. yes if the timing wasnt changed
but if you reduce the timing its gonna end up with
a wider burn mark and its usually better to start with
fresh plugs.. but I usually just put in 1 or 2 plugs
for a reading then if it looks better/right then I
change the rest to get a full engine reading

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Good to know, I've been wondering about this.

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I pulled 2 plugs today on my street rod... seen that
I'm a couple degrees high on timing and its still rich..
I checked them because I'm going on a run tomorrow
with a lot of X-way running and I wanted to make sure
I wasnt lean.. I pulled 2 degrees of timing and left
it on jetting till after tomorrow

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fine with me I still would like you to explain how it can single out the ground strap and change it.

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Simple... start the burn earlier and the temp in
the cyl goes up... if its later it cooler and burns
more in the pipes... I have backed the timing down
on my junk and seen the color move closer to the tip
of the radius on the strap... this is fact not just a
opinion

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but don't loose sight of the fact that we are not adjusting timing or A/F to make the plugs look happy. Gotta make adjustments in those areas for best HP or at the track, best MPH. Then correct plug choice so they are happy and live for a while - which I can't seem to accomplish.

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I know your playing with a boosted engine so on yours
are the plugs fouling out or burning up

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Right now they are fouling out Mike. I can get about 4 - 5 runs on a set of plugs before I start to experience a high boost miss. Pretty sure I am way rich, but won't know until Saturday when I can make some WOT runs at the track without the exhaust system on it. Camera should tell all ( pointed at the A/F and boost gauges), plus I will be able to cut it off clean at the end to examine the plugs properly. I'm running 110 leaded gas.

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Will it usually stay in the same spot though?

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