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

[pantdino at aol.com]

My understanding is that if a piston contacts a valve, the valve bends 
and it would not seal at all.
Your plan sounds like a good one to me and is what I would do.

I'm not so sure I share your high opinion of the carb rebuilder, 
though. Seems to me like making sure the secondaries to open is a 
pretty basic thing.  If he doesn't apologize or admit his error I 
wouldn't have any respect for him.

-----Original Message-----
From: Dan Courtney <dfcex at pacbell.net>
To: detomaso at realbig.com
Cc: Jack DeRyke <JDeRyke at aol.com>
Sent: Fri, 29 May 2009 10:20 pm
Subject: Re: [DeTomaso] WARNING: .050 may be the wrong kind of Bomb / 
Borescope










I purchased a borescope, pretty cool tool!
In looking inside the cylinders I see #6 (second broken plug) and #7 
look fine.
Nice milk chocloate color. I can even read the #7 etched into that 
piston.
#5 (with the most broken plug, missing 1/2 the "J" tip and the 
compression
reading that didn't show until I squirted oil into the cylinder) shows 
about 30
shiny little "nicks" on the bottom half of the piston. The upper half 
looks fine
and even has good color.
I'm not certain yet if this was caused by detonation, the missing plug 
tip
bouncing around, or valve contact (this seems unlikely, as they are 
pretty small
nicks and dispersed around a somewhat shinny 2" or 3" area.)
I didn't see any spark plug pieces in there and I could see the oil 
around the
perimeter of the piston.
I also ran a magnet around the piston and nothing came out.
I suppose I could do a leak down test to see if the valve's are 
sealing, but
with this small amount of oil in the clylinder the compression is 
testing just
fine (180 psi). The other cylinders all tested at 150 psi, which seems 
low.
I'm wondering if the damage to the plug's kept this hole from firing 
properly
and if the cylinder got washed down and kept the rings from sealing.
Given that the other pistons look fine I'm not positive these nicks 
were caused
by detonation or the broken spark plug pieces. I've experienced 
detonation
before and there is usually a rattle. Either way, the piston does not 
appear to
be badly damaged.
I may try putting the plugs back in and running it, to see how it 
sounds.
If it's favorable I will ease it the four miles to the local 
performance shop
(JBA) to let those guys do an inspection, leak--down and dyno. That 
drive should
burn the oil out of the cylinder and I can then run another compression 
test on
#5. I'm bringing the Holley back to the fellow who rebuilt it, who has 
an
excellent reputation. He'll get the secondaries working properly, no 
question.
My other option is to pull the head, but I'm hoping to get lucky.
MAYBE I caught it in time, this time around.
Trying to stay positive and keep working at it,
Dan.

Dan F. Courtney

La Jolla, CA

(858) 551-5455 Phone
(858) 551-5456 Fax
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