[DeTomaso] WARNING: .050 may be the wrong kind of Bomb

[pantdino at aol.com]

My understanding is that a too-hot plug will get superheated at the 
tip, which will possibly cause the ceramic to fail.  A very hot tip 
could then also serve as a source for detonation.  The shock wave from 
that will damage the metal of the plug.

But why do some plugs look fried and damaged from detonation and others 
look good or fouled?
My understanding is that a lean mixture will cause detonation and 
piston-top damage and will make a hole in the piston if it continues 
long enough.

So it sounds to me like your intake manifold is not delivering equal 
mixtures to the cylinders.
The fried plugs didn't look that way after mixed driving because when 
you accelerate the accel pump dumps in some more gas to richen the 
mixture.  But after 400 miles of 3500rpm on the carb cruise circuit the 
lean conditions took their toll.

But Jack knows 1000 times more than I do.

Jim Oddie




-----Original Message-----
From: Julian Kift <julian_kift at hotmail.com>
To: dfcex at excaliburre.com; rimov at charter.net
Cc: De Tomaso List <detomaso at realbig.com>
Sent: Sun, 24 May 2009 12:02 pm
Subject: Re: [DeTomaso] WARNING: .050 may be the wrong kind of Bomb











The plug electrode damage may be self destruction due to 
heat/detonation. Too
hot a plug in some cases will create detonation, especially if you are 
on the
verge of being there anyway. FWIW I run the Autolite AR
-32 plug, which 
as I
undestand it is one of the colder plugs Autolite manufacture.



Julian
> From: dfcex at pacbell.net
> To: rimov at charter.net
> Date: Sun, 24 May 2009 08:14:11 -0700
> CC: detomaso at realbig.com
> Subject: Re: [DeTomaso] WARNING: .050 may be the wrong kind of Bomb
>
> Paul, very high dome pistons.
> This is why I had to go with large cc heads, to keep the compression 
around
> 10.5:1.
> The valves are brand new Ferera's, not cheap.
> But I'm not sure the damage to the plugs was caused by contact. On #6 
the
> tip is still intact, yet the electrode is eroded aprox. 1/4" below / 
inside
> the threaded case. On #5 the tip is 1/2 intact, and the electrode is 
about
> 1/3" down. I don't see how the electrode could have been impacted 
while
> being "blocked" by the tip. The tips don't look bent, either.
> If the bits and pieces are already gone, I'll proceed to check the
> compression and leak-down.
> Assuming it checks out I'll add a couple more rings and go with .045, 
then
> take it to the Dyno Shop to check the advance, etc. I was thinking 
about
> having it dynod anyway.
>
> Dan
> Dan F. Courtney
>
> La Jolla, CA
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