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Dr. Z06 = KABOOM


Dr. Pomade

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and now that i have removed a motor out of a corvette i now hate them. as for the hole....wow ....and also 5 out of 8 plugs had nothing left of them. but the good news is after the engine is out u can see all kinds of places to stuff some snails. hint hint
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If you're going to blow something up, I guess there's no use in only blowing it up a little.

 

That is only a little blown up.

 

If you wanted to do it in a grand fashion, you would have put a hole in the block or driven over the crank. :)

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You got any clearer pics of that Tilly? I love the way that everyone seems to be trying to diagnois the failure on that cylinder without being able to CLEARLY see the marks in the top of that piston.

 

The harsh reality is that other than it maybe being a tad rich (indicated from the black on the top of the piston, those pics are too blurry to see what did this in.

 

And the ones screaming detonation. You might consider that the color of that specific cylinder is much lighter than the others, indicating a lean condition. And since everyone else seems to what to guess, I will throw mine in too, and maybe Tilly will be kind enough to spill the beans about what actually happened.

So my guess is that the marks are aluminium from when the hole got burnt in the piston caused by a lean condition, most likely because of either a plugged injector or a plugged nitrous fuel nozzle. That cylinder ran out of fuel to burn, becuase it was so lean so it started burning the aluminium in the piston top. If Tilly would be so kind as to tell us if the marks are raised up or if they are indentations on the top of the piston, and maybe show a pic of the sparkplug, and the head, specifically the chamber of that cylinder, we would all have a better idea.

 

But, like I said, I am just guessing, but my guess has little to do with detonation.

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It's funny Despo, you poking at people trying to diagnose this failure, but then trying yourself. So you think it was lean enough to somehow “start burning the aluminum in the piston top”, but didn’t detonate? Please, explain to me exactly what it is you think happens when an engine runs lean. Oh wait, never mind, please don’t. :p:D

 

As has been mentioned, 5 of the 8 spark plugs are completely destroyed, the remaining 3 look like shit too. This, along with the hole in the center of the piston is nearly a textbook case of detonation induced pre-ignition. For those of you who didn’t know, detonation and pre-ignition are most definitely not the same thing. Detonation occurs after a spark induced combustion event, pre-ignition occurs before the spark.

 

The car was likely detonating due to being too lean, or to running too much timing, or both. It was pretty cold out that evening, which would cause both a leaner mixture, and slightly advanced timing, since stock ecu’s like to advance timing when it is cold out, and since the stock maf calibration adds only enough fuel trim based on cold charge air for a stock engine. My guess would be John's car was too lean, since too much timing tends to kill headgaskets first. I know my car would lean out a bunch on cold nights even though the tune had been perfect just the weekend before, I only caught it because I had a wideband in the car. It's possible his fuel pump was starting to fail as well, at this point who knows. Regardless, all of the hurt plugs indicate that it was not just one cylinder that was having problems, likely many of the cylinders were detonating. It's just #2 that crossed over to pre-ignition, and total failure, first.

 

A strong engine will live through quite a bit of detonation, but it will not live for more then a couple seconds of pre-ignition. The detonation (be it from a lean mixture or too much timing or whatever) caused high combustion chamber temps and pressure spikes, which destroyed the plugs, and turned them into some nice hot glow plugs. Having a hot spot like a glowing plug will cause the fuel to ignite while the piston is on its upstroke, known as pre-ignition.

 

The piston is trying to compress an already burned mixture, which of course causes the various parts to absorb heat very quickly. The cylinder head and cylinder walls have high thermal inertia, so that is why they survive. The center crown of the piston is very thin relative to the outer circumference, and has nowhere to reject heat like the ring lands do (to the cylinder walls). So that is why the center of the piston gets knocked out in this fashion, since it has such a low thermal interia, and is pushed past it’s failure point by the raised temp and pressure very easily.

 

The pistons are black because the car was driven from Sam’s house to the shop. John knew it was hurt already, and they had it up and running a few times at Sam’s anyway, so they figured why bother towing it. So the color of anything in the combustion chamber is far from representative of how it was running when the failure occurred. Driving a car when it has a bunch of beat up spark plugs tends to make the combustion appear a bit on the rich side. ;)

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Well, that definately sucks. Did the head survive, or will it need some work too? I tore up one of the pistons on my boat like that; screwed a couple of the valves up pretty nicely in the process.

 

Luckily, you have tons and tons of options to go with, and some really cool new stuff is just coming out too. Dart's new blocks/ 5-bolt heads have just been released, E-performance has their new 11 degree badass heads out now as well.

 

Could always go w/ an LS7 crate motor w/ a cam swap and 250 shot; that would probably net a nice 750+ RWHP number without a ton of work and still be very streetable.

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Renner,

Great description of what happened. Thats really what this board needs. GOOD car information and knowledge.

 

Dr. Z06,

Man that sucks your car is down from what seems to be something as simple as a tune being off because of the colder weather.

Good luck on what ever is next. I am sure it will be fast. :)

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Renner,

Great description of what happened. Thats really what this board needs. GOOD car information and knowledge.

 

Dr. Z06,

Man that sucks your car is down from what seems to be something as simple as a tune being off because of the colder weather.

Good luck on what ever is next. I am sure it will be fast. :)

 

Thanks. Just thought I would mention, I don't know for sure if the detonation was from cold weather or not. That's just an idea that I think could have happened, because I know that going lean from air temp often happened with my car. As John said in another thread, when you make power, shit happens, stuff breaks, and usually you can't do much about it. You fix it and move on. :)

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No race this year :(?

 

Just make sure you tell the guys at ips not to send any motors to the same machine shop mine is in. Unless of course you don't want your car back till 2007.(Assuming you'll goto ips)

 

But hopefully all this time means something is getting done right.

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Rane, did you really want to race me? As lean as that fucker was, I was probably putting down close to 700rwhp. :)

 

Of course the car is going to IPS. As I've said a time or two before, they are the only people who have earned my trust to even touch the car.

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