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

[Dan Courtney]

I tried the compression test again on #5 last night, because on the first test the other seven cylinders only took 2 or 3 revolutions to get a reading and it took me allot more on #5 (the cylinder with the most electrode damage).
This time I could not get any reading at all.
I pumped a little oil into the cylinder and it immediately registered at 200 psi. After letting some of the oil escape it dropped to 180, but still registers consistently, and immediately, at 180.
I believe this indicates the rings were not sealing?
Sounds like I either have a broken ring or they got washed out.
I took another look at the carb linkage. The rod the rebuilder put in for the secondaries appears to be way too long and the linkage bottoms out on a stop well before the rod can open the secondary butterflies.
I floored it a couple of times on the way back from Vegas for a 1/2 mile here and there and I'm thinking this made it go lean and caused detonation and/or washed out the rings with excess fuel. I never exceeded 4,500 rpms and it was flat above 4,200.
There is a nearby shop with a borescope so I might trailer it there tomorrow.
I also have a mobile mechanic who can swing by tonight and run a leak-down test.
Or, I can just start pulling off the head.
Here I go again, after only 800 miles on engine #5, which was supposed to be a keeper.
As you can tell from this email, I'm assuming the worst. If you think I'm missing something please let me know.
Unfortunately, it took me the 1 1/2 years to get this running because I'm pretty fatigued about having to constantly get new engines and I've lost allot of my enthusiasm for driving a Pantera. What I really needed was a good year or so behind the wheel with no blow-ups. 
Anyway, such is life.

Dan

Dan F. Courtney

La Jolla, CA

(858) 551-5455 Phone
(858) 551-5456 Fax
  ----- Original Message ----- 
  From: JDeRyke at aol.com 
  To: dfcex at pacbell.net 
  Cc: detomaso at realbig.com 
  Sent: Thursday, May 28, 2009 11:18 AM
  Subject: Re: [DeTomaso] WARNING: .050 may be the wrong kind of Bomb


  In a message dated 5/28/09 11:10:02 AM, dfcex at pacbell.net writes:


    Could impact from the domed piston to the plug tip crack the electrode without breaking the tip? Although #5 is missing 1/2 the tip, #6 has an intact tip but not much electrode.


  Unless you're running side-gap plugs, first contact will be between the piston dome and the ground electrode, essentially shutting off that plug as the gap goes to zero. Busting up the ceramic inside won't necessarily shut down the plug sparks, if the ignition is energetic enough. I'm still thinking an over-lean mixture at higher rpms causing detonation. Good luck- J Deryke



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