c0ncEpT

Needs steel pistons

BigSilverCat

not sure but I think 65lpm 118' , and 1000 pulse width. not sure what the timing was.

kidturbo

Lavon's engine actually looks better in person.. Obviously a block failure, casting defect or just good old fatigue. Compressing 10 atmospheres by a multiple of 15, then shooting massive amounts diesel fuel into it, might of had something to do with it...

What's more amazing, that bone stock 6.7L OEM crank survived, when it ripped the piston pins clean out of the rod ends on 1 & 2. So I wouldn't worry to much about his type of failure at your power level. Those cylinder pressures were just crazy high, and block couldn't handle it.Your piston pics are not what I expected to see. That's sure look more like ring land failure then any burnt diesel pistons I've seen before. Going back to what Joe stated about expansion couple pages ago. But ultimately it's still a piston failure, and there's a known fix for that.

Lavon's engine builder did actually offer up an angle kinda in line with your lean out thoughts. But rather than overall engine fueling being a cause, he claims intake designs can cause lean conditions on the end cylinders. Personally I don't see it, but have no experience with the different Cummins intakes out there. But if air isn't flowing equally to every cylinder, then I guess it plausible.

outonsafari

iTrader: (4)

i watched this thread over the past couple weeks after the engine failure.
read all the posts good bad or indifferent, some genuine pros, some not,

one thing that was never asked "hows the other engine" ?
i would want to pull the head and look down the holes on the
other engine right after the other head came off and the gasps stopped !

knowing less than zero about diesel, to me it would say tune or
mechanical failure depending on what the other engine looked like

SB

iTrader: (1)

Most definitely.

BigSilverCat

I think what happened was the tuning not knowing what to do with the proposing of the boat or the blowing out getting on plane so the timing and pulse width were changing compared to what it was on the dyno. I think the piston looks like detonation broke the piston (here goes another fight, I know its not a gas engine and that a diesel engine by definition runs on detonation, ect,ect.) and then it leaned out to fuzz up the edge. Or the piston swelled and grabbed the cylinder wall and ripped the top ring land off (because it was running lean .)

.

HabanaJoe

I'll start giving you crap first!!!

So you agree with me maybe? Or the piston swelled and grabbed the cylinder wall and ripped the top ring land off (because it was running lean )

I think you're right the timing got way off and but again 180 deg from you but I think you have extra fuel (running rich) running off the top of the piston down toward the land and when the piston breaches TDC the fuel there ignites and causes the swell because it appears to be from the outside inward. The cylinder is at it's widest point at the Top because the gasket, o-ring or liner seal is usually larger in Dia than the cylinder so flame spreads out larger than the cylinder Dia. and then when the piston tops out the flame pushes down the side.

I think you are looking at the hopping again 180 deg from me, when you hop we both agree you go from Full fuel to Idle in split seconds, I think it's the over fuel event is what caused that not the under fuel event?

Do you have a picture of a piston out of the engine from the side close up near the top I would like to see the profile - we solved many a problem like this by re-machining the top edges different than stock.

I've melted a few (mechanical engines in the dark ages) but what I see looks the same as many I held in my hand going WFT, I thought "lean" as well. An old guy at Holset who helped us with turbos heard of our problems and wanted to see the damage, it took him .1 seconds to look at it and say "swelling, piston is shaped wrong"

If I'm right do I get a ride someday?

stirling

There,s only one piston with this type damage? You might want to check THE piston oil squirter on that cilinder , it can BE out, or plugged or whatever... if Its warming up , it could BE expanding and score THE liner..

HabanaJoe

I will throw one other thing out there for discussion, I think you choose to raw water cool these engines? The 6.7 I think is still a liner-less engine, unless you added liners? Without closed loop pressurized cooling you can get and trap air in the block and the hottest spot is at the top of the cylinder. The iron block does expand or the cylinder diameter decreases at the top in overheat which might grab a swollen piston as well. I know the machined steel liners are more stable than iron, heat transfer not as good because it is a dry liner then but a thought. We would sleeve the 5.9's for what it's worth.

Which cylinder had the problem if I missed that part?

BigSilverCat

It was cylinders 3 - 4 - 5 they all looked about the same.