Well after pulling off the head each one of my pistons has detonated. It is really wierd looking detonation though, it's not the normal pitting you can see, it's almost like someone took a carbide bit and grounded off the tops of the pistons. And there is a gray/light brown residu on top of all the pistons. If I run my finger across the piston I can get it on my finger.
What do you guys think? Again I was running 112, 15-16psi, 10,000 ft 134.5 mains and 9:1 static. I just don't know why I would of detonated this being the case?
What do you guys think? Again I was running 112, 15-16psi, 10,000 ft 134.5 mains and 9:1 static. I just don't know why I would of detonated this being the case?
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How hot was your engine? Did this happen after a few long-ish pulls by chance? Hard to tell from the pics, but that residue on the pistons is probably anti-freeze.
Gray residue could also partially be from leaded race fuel. As lakercr stated anti-freeze in the combustion chamber is a BAD thing. Since that liquid does not compress, depending on severity, it can reduce combustion chamber volume, increase your compression ratio, which leads to big problems. Looking at the color, consistency, and surface damage to the pistons I find it unlikely that all four cylinders could ingest anti-freeze in the exact same amounts to maintain that level of consistentcy in form and coloring. Looking at the crescent shaped white/gray areas on both the intake and exhaust sides of the piston edges, and lack of anything resembling residual carbon, I'm seeing things got REAL HOT in the combustion chambers. Excessive combustion chamber heat will cause pre-ignition. Excessive turbo backpressure is also BAD and it can push exhaust back into the combustion chamber causing burnt/bent valves and excessive combustion chamber heat. High intake charge temperatures and engine coolant over-temperature can cause excessive combustion chamber temperatures. Falling fuel flow/pressure can also cause a lean condition, regardless of jetting, and create excessive heat in the combustion chamber. The result would be pistons that look very-very similar to the pictures you posted. Plug checks are the final word on fuel and I only use my O2 sensor as a reference tool for what the plug checks are telling me.
HAMMER said:
Agreed. I asked about the pulls because the motor looks very hot. The thin film of dust on the pistons sounds like anti-freeze.
Hi
Can you please post what the symptoms were and what lead you to tear the head off?
Can you please post what the symptoms were and what lead you to tear the head off?
lakercr said:
It was after 6 8 sec pulls. I didn't smell antifreeze, although that doesn't rule it out. My hg seemed to be fine when I pulled it.
HAMMER said:
You bring up some good points. I need to get a fp gauge and make sure I'm flowing enough fuel on top end. I've never had to add antifreeze. I'm actually pretty good on checking and reading my plugs, they actually don't look that bad right now. I thought that with that kind of detonation I it would of eaten up my plugs, or given me more of a warning. Backpressure shouldn't be a issue for me, I have a 2871 ported turbine housing, and my own made 2.5" TH dump pipe. I'm anti backpressure
olddodge said:
Sorry, should of posted the link. Here you go.
http://www.ty4stroke.com/viewtopic.php?t=50541
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Man O man, you cant catch a break! Sorry to hear this.
In my opinion, the grey is from your fuel. Your plugs should look this way aswell.
The pistons look like a typical lean detonation on a four stroke. The brownish flakes on the tops are from heat. There is not a huge amount of damage done to the pistons, but enough that it probably lined the cylinders well.
I can show you pistons from my four wheeler that looked identical to that from burning it down from lean conditions using alot of nitrous.
Again, just my opinion.
Hope you get it back together soon. I was looking forward to seeing you folks up at Tower next weekend!
In my opinion, the grey is from your fuel. Your plugs should look this way aswell.
The pistons look like a typical lean detonation on a four stroke. The brownish flakes on the tops are from heat. There is not a huge amount of damage done to the pistons, but enough that it probably lined the cylinders well.
I can show you pistons from my four wheeler that looked identical to that from burning it down from lean conditions using alot of nitrous.
Again, just my opinion.
Hope you get it back together soon. I was looking forward to seeing you folks up at Tower next weekend!
Ya Jed, I'm pretty frustrated. I just wish I knew what the actual problem was. Things should be silly up at Tower. It would be worth going to just watch. Lets make a trip to Tony's soon.
Ended up being a rod bearing. The pistons did have a little detonation on them, but not enough to seize the piston. The cylinders were fine, but I need a new crank and rod. When I pulled the engine and oil resivour there was a oil line that had a kink in it. A really bad kink that I think starved it of oil.
I'm actually glad it wasn't melted down because of detonation because that really didn't make sense to me for how low of boost and the good gas I was using. I know detonation can cause a rod bearing to go, but I think it was more of the oil issue then detonation.
I'm actually glad it wasn't melted down because of detonation because that really didn't make sense to me for how low of boost and the good gas I was using. I know detonation can cause a rod bearing to go, but I think it was more of the oil issue then detonation.
wantboost
Expert
zross1 have you ever had any cylinder repair done? if you have you may be missing a oil restrictor.oh yea i saw a couple of sets of rods/pistons on ebay mon.
This is the first time the block has been cracked. No cylinder work has ever been done. Thanks for the heads up though.
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