Reading Plugs

[AMXguy]

Looking at the plugs on a fresh built engine, how long do you wait until you can assume they're telling you anything?

Have a fresh built 383, pretty stock 10.1 compression, 270 cam , stock intake and exhaust. running a new 650 double pumper with stock jets, 3000 ft elevation.  runs great, no issues at all.

plugs have a little dark gray ( not silver ) and a little brown but overall much cleaner than the usual brown I'm used to.  it's had three 20 minute break ins and about 20 miles of street driving with no idle time.  should I jet up now or wait to see if they color up?   

[cudabob496]

from what you say, jetting up does not seem necessary.

you'll need at least 1000 miles on engine for rings to seal properly, I think.

Also, on break in, plugs might not tell real story, cause of all the stuff burning off, etc.

I'd wait 1000 miles, and read them, unless you have an AFR meter.

[Chryco Psycho]

 You can color plugs in 1/4 mile so 20 miles on the street will give you a good idea where you are at , generally you are looking for a light tan color but with todays fuels the only real way to know is with an O2

[AMXguy]

I have quite a bit of experience reading plugs on snowmobiles, and you really have to be lean to hurt anything except at WOT. I assume a 4 stroke is the same?

Is there really much danger on a street driver if it's on the lean side?   I can jet it up I'm just not sure if I'm helping or hurting . as a rule I run things too rich.

[Chryco Psycho]

safer on the richer side for sure

[cudabob496]

can read plugs after 1/4 mile?  would have thought engine had to be broken in more? oh well.

anyway, lean is more dangerous. Detonation, and things can get really hot/melt.

Fuel acts as a coolant.

Could tell when my engine was too lean because I would run out of power at higher rpms.