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Discussion Starter · #1 ·
Well, I am at a loss here. I have a 2001 Z06, and started hearing a very disturbing sound from the top end of my motor at just 39K. After reading the forums, I suspected a faulty valve spring was my culprit. I found my number 2 cylinder was running about 30lbs light on compresssion and lost 24% on a leak down test. At this point I was still thinking valve spring. Did a wet leak down test with oil in the cylinder, had vey similar results - about 19% on leak down. Here is where it gets tricky, my mechanic tour down the valve train and called me to say everything on the top end was in good shape and he suspects I blew a ring and the engine should be replaced. The electrode on the number 2 plug as acutally bent to the side. The engine actually runs fine, minus the loud ticking. Obviosly I have not tried to push the car since this started. Any advice? BTW, quote I got for crate motor and install was $9k - Ouch. If a new motor is needed, wouldn't a rebuild be much cheaper and bore this baby out for a few more ponies? I really don't want to go over $3k to fix this, dont' want to and can't afford to. Any advice would be appreciated.
 

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Discussion Starter · #3 ·
Well, it turned out to be a foreign object found its way into my #2 cylinder and destroyed the piston. Miraculously the cylinder and heads are in great condition. My new piston should be here tomorrow. One theory is that the cylinder was starving for oil and had a momentary seize that broke the ring land. The broken metal then got beat around and eventually worked its way out the exhaust valve. The amazing thing is my valves have no marks on them at all. While I am down in the engine this far, would it be worth throwing on a new set of heads. Just did some pricing, I can get a set of patriot heads from summitracing for about $1400. Does anyone have experience with these heads (summit racing, patriot ls6 heads How much could I get out of my stock heads? Any advice is appreciated. Thanks!!
pics of my ls6 motor with #2 piston damage
 

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There was some bad press on Patriot heads awhile back. I believe that they have resolved all there problems. You might want to go over to http://www.ls1tech.com/forums/index.php? and do a search.

You might as well toss in a cam while it's down :z:
 

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Whata,
I would think the FOD bouncing around in the cylinder/combustion chamber would at least beat up the chamber and the quench area as well. You would a least see where it knocked off the carbon that is unless you drove a while after the part made it's exit. Have your mechanic pour some mineral spirits down the intake and exhaust runner to see if you still have a good seal between the valve and seat in that cylinder at least. If you are not going with the new heads, etc I would at least touch up the valves and seats and replace the seals. Springs may me in the offing as well. I would have it pressure tested as well. It's cheap insurance.

It's your money,

D.J.
 

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Discussion Starter · #6 ·
Started looking for what the foreign object was in my cylinder. I found some small metal pieces in my intake manifold. Has anyone heard of pieces breaking lose from within the manifold? The screen on the tb would not allow anything to come through. See the pics below, the last one are the metal objects I found in the manifold. I don't think they came from the manifold, since it is a composite plastic and the pieces seem to be metal. I do not want to be in this situation again, so I probably will replace the manifold. It seems the stock LS6 intake manifold is the best bang for the buck, anyone disagree? The net net is that, the piston and connector will be replaced and potentially the intake manifold. The ring land on the cylinder was pinched and stuck in the side of the piston. Surprisingly the ring land was all intact though. If anyone has seen anything similar, please let me know.

The link below has 3 pages of pic of what I have encountered. Pic 16 and 25 are the metal pieces I found in the intake manifold

z06 motor pics
 

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Did you look at the MAP sensor to see if it's all intact (rear of intake). I can't think of anything that would break off inside the intake like that! Let's us know what you find.
 

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I don't know if this will ease your mind, but on NHRA today last weekend they had a bit on engine failures. Pieces from any component failure in the combustion chamber will be blown back into the head and out the exhaust. One of the ProMod guys had a big bung and plug put into the front of the intake to make it easier to clean the intake out!!

Ken
 
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