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

[Dan Courtney]

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