Part 2: Reading Plugs, pistons, and valves (with Pics)

[Bruce Plecan]

> What I see is the thickest,blackest carbon is built up around the
> edges of the piston, except the area under the intake valves which is
> clean.

Relatively cool fuel keeps washing the carbon off

>  What I would think is that the combustion temps are lowest at
> the outside of the chamber.

Yep, you want the quench area *cool*, that is where detonation usually
starts.  Recation pretty well over by the time the flame gets out there.

> Between the low temps and the incoming
> fuel wash there's no chance for carbon to build up on some areas of
> the piston. In general the outside edges seem to have that
> "looser","flaky" carbon buildup while the insides have a sort of
> "glazed" or "cured" buildup.  Again, heat...
> Finding the why of low temps is the thing....
> Yeah, too much fuel.  Yeah, too cold t-stat.  Yeah, too cool intake
> charge.  Yeah, fuel issues.  Yeah, insufficient spark to ignite a good
> burn. Yeah, aluminum heads draw heat from the combustion chambers and
> they're cooler in the back than the front due to coolant circulation.
> Yeah, it all works together.  But what is the one thing that's doing
> it??

It's too rich for the combination of all those factors.
That why when changing thermostats, you need to retune things.
That's why you have to look at sooo many variables.
Like I've always said too often too cold of operating temp, too warm of
plug, and toss in a few degrees of timing error and things can look copa
setic.
You have to experiment.
You have to find out what is true, especially for your combo.
Rich cylinders?.  Or lean cylinders?.
Look at the SBC cooling system, it's a nightmare.  Even the reverse cool one
is 1/2 wrong.
Lower the operating temp even worsens it IMO, course I got too many opinions
THOU THERE ARE Some truths.
HTH
Bruce
>
> Or is it one thing?
>
> Now you guys know what you've been discussing, I haven't followed as
> closely as I could.  But I would look at this and think about heat,
> chamber temps, and the causes of more or less of it.  Then I'd prolly
> work to rich, or wrong plugs, or cool engine temps, whatever.
>
> I'd be nervous about starting at "too rich" and working my way back to
> carbon buildup, since I already know that too rich leads to carbon
> buildup and I have the answer before I ever get serious with the
> question.
>
> Am I off the wall?
> Hmm...  Let me rephrase that.
> Anybody wanna correct/add/subtract something?  I'm still a thoughtful
> beginner....
>
> Shannen
>
> Programmer wrote:
> >
> > Yep--that's right. <g> Probably couldn't
> > be any deeper...sure looks rich around the piston
> > edges. What's the plug part numbers btw ??
> >
> > Lyndon.
> > ----- Original Message -----
> > From: <timsiford at hushmail.com>
> > To: <gmecm at diy-efi.org>
> > Sent: Saturday, December 02, 2000 7:00 PM
> > Subject: Re: Part 2: Reading Plugs, pistons, and valves (with Pics)
> >
> > > I thought that the plugs had the correct reach.  But, then again, what
is
> > > the 'correct' reach?  From the Pics you can see that only the end
portion
> > > of the plug was in the chamber.  That looks good to me.  Is that
right?
> > >
> > > Tim
> > >
> > >
> > > At Sat, 2 Dec 2000 18:43:56 -0700, "Programmer" <nwester at eidnet.org>
> > wrote:
> > >
> > > >
> > > >Looked at the pics...Shouldn't those plugs have a taper seat ? Did
they
> > > >sell
> > > >you plugs with the wrong reach ??
> > > >Orange is just fuel additive package...looks like it was
> > > >definitely on the fat side of tuning.
> > > >
> > > >Lyndon
> > > >----- Original Message -----
> > > >From: <timsiford at hushmail.com>
> > > >To: <gmecm at diy-efi.org>
> > > >Sent: Saturday, December 02, 2000 4:45 PM
> > > >Subject: Part 2: Reading Plugs, pistons, and valves (with Pics)
> > > >
> > > >
> > > >> I have pics of my head gasket swap (teardown).  Any advice you can
> > > >offer
> > > >> would be great.  All in all ... I 'think' everything looks good.
> > > >But,
> > > >this
> > > >> is only the second time I have had the heads off.  The only problem
> > > >is
> > > >that
> > > >> I see lots of Orange.  I don't know why everything is so Orange.
> > > >Anyone?
> > > >>  I have pics of the plugs, the pistons, and the head chambers from
> > > >each
> > > >> side.
> > > >>
> > > >> Also, these pictures clearly document how the rear cylinders run
rich
> > > >with
> > > >> the TPIS MiniRam.
> > > >>
> > > >> Go to ...
> > > >> http://www.picturetrail.com/traxion
> > > >> Click on '1990 IROC Z28 Pictures' and then you can view thumbnails
> > > >on the
> > > >> left.
> > > >>
> > > >> BTW - www.picturetrail.com is pretty cool.  I uploaded all of my
pics
> > > >through
> > > >> this free service.
> > > >>
> > > >> Again, any advice or help is appreciated.
> > > >>
> > > >> Tim
> > > >
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> >
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