Failure analysis leads to rebuild along with a cleanup.
02-19-2012, 01:12 PM
#1
Failure analysis leads to rebuild along with a cleanup. First let me say that this isn't anyone's fault other than my own... no sponsors or shops had their hands in this.
Stock shortblock ls1 circa 2000 with 60,000 miles on it. Heads are PI 215s, FAST 90 intake, 227/235 cam, longtubes, head studs, 60# injectors, oh, and a procharger pushing 14# at 6400.
My tune was overly way to rich. In boost I was starting at 10.4 and slowly going up to 10.7 by 6400. Timing was only 13-14 degrees. IAT's were very good, only 4-6 degrees above ambient after a 3rd gear pull from 3000-6400rpm.
I knew I was on borrowed time with the motor as stock pistons usually won't handle that much power, but I'm trying to learn what went wrong, so the new forged shortblock won't be hurt.
Here's what I found after a short 4th gear highway pull (3500-5500rpm) resulted in a puff of smoke.
I pulled #7 when I got home:
So I knew something had to have hit the spark plug on #7, which I figured was a cracked ringland, and sure enough, I got the head off and this is what I found:
While the motor was in the car, I checking the walls to see if I had any other damage, and I thought it was fine. Then I got the motor out and was able to inspect further and found this:
The crack into the water jacket explains why I was down on coolant when I got home and checked. It also explains why my catch can was full of water as well. That is the #7 cylinder
I know part of my issue surround the use of the FAST manifold and that I had blocked off the rear steam vents in the heads, which I'm rectifying by running lines from them to the front ports and back to the radiator.
I understand, at least I think, why I cracked the ringland, but what caused the crack in the block? I wasn't data logging when it happened, but had been earlier in the day and everything looked great. Ambient temps were in the 38-40 degree range, and my iat's were right around there as well, even in boost. I wasn't getting any knock at all, and like I said, I was running low timing, 13-14 degrees, and from what I've been told, I was too rich, 10.4-10.7. I always run 93 octane if that matters.
I'm putting in a forged stock bore rotating assembly, but I plan to get another ls1 block. I don't want to make more power, but I don't want to have to worry about the motor either.
Thanks.
__________________
Stock shortblock ls1 circa 2000 with 60,000 miles on it. Heads are PI 215s, FAST 90 intake, 227/235 cam, longtubes, head studs, 60# injectors, oh, and a procharger pushing 14# at 6400.
My tune was overly way to rich. In boost I was starting at 10.4 and slowly going up to 10.7 by 6400. Timing was only 13-14 degrees. IAT's were very good, only 4-6 degrees above ambient after a 3rd gear pull from 3000-6400rpm.
I knew I was on borrowed time with the motor as stock pistons usually won't handle that much power, but I'm trying to learn what went wrong, so the new forged shortblock won't be hurt.
Here's what I found after a short 4th gear highway pull (3500-5500rpm) resulted in a puff of smoke.
I pulled #7 when I got home:
So I knew something had to have hit the spark plug on #7, which I figured was a cracked ringland, and sure enough, I got the head off and this is what I found:
While the motor was in the car, I checking the walls to see if I had any other damage, and I thought it was fine. Then I got the motor out and was able to inspect further and found this:
The crack into the water jacket explains why I was down on coolant when I got home and checked. It also explains why my catch can was full of water as well. That is the #7 cylinder
I know part of my issue surround the use of the FAST manifold and that I had blocked off the rear steam vents in the heads, which I'm rectifying by running lines from them to the front ports and back to the radiator.
I understand, at least I think, why I cracked the ringland, but what caused the crack in the block? I wasn't data logging when it happened, but had been earlier in the day and everything looked great. Ambient temps were in the 38-40 degree range, and my iat's were right around there as well, even in boost. I wasn't getting any knock at all, and like I said, I was running low timing, 13-14 degrees, and from what I've been told, I was too rich, 10.4-10.7. I always run 93 octane if that matters.
I'm putting in a forged stock bore rotating assembly, but I plan to get another ls1 block. I don't want to make more power, but I don't want to have to worry about the motor either.
Thanks.
__________________
Last edited by The Alchemist; 03-18-2012 at 10:53 PM.
02-19-2012, 05:38 PM
#4
your afr was rich but not crazy. i start off around 11.2 and taper into 10.7-10.8 with similar timing. not being ideal afr and the rear steam ports probably didnt help, but you might have just pushed the stock piston too far. that setup has to has a shitload of cylinder pressure for stock pistons. do you have an estimated power level? what is your duty cycle on those 60#'s? for reference i saw about 77-78% @ 600 rwhp
02-19-2012, 07:53 PM
#6
Nope. It was probably an 80:20 mix of water to coolant, but never saw feezing temperatures as it hibernated in my garage during the winter and the garage doesn't get below 48-50 degrees.
Ummm, yeah, lets just say I ran out of injector above 6400 rpm. Soooo, if you were making ~600 at 77-78% duty cycle, I was a good amount above that. Needless to say, the 60's are going and I'm moving up to 80s.
Yeah, I'm hearing that is part of the issue, not saying having all four steam ports connected would have saved me, but chances are it might have lasted a little longer or maybe it would have been another cylinder first.
I'm asking these questions because as a scientist, I don't get discouraged by mishaps or setbacks. I try to dig deep into the result, and figure out how I got there, and how to avoid the same outcome.
your afr was rich but not crazy. i start off around 11.2 and taper into 10.7-10.8 with similar timing. not being ideal afr and the rear steam ports probably didnt help, but you might have just pushed the stock piston too far. that setup has to has a shitload of cylinder pressure for stock pistons. do you have an estimated power level? what is your duty cycle on those 60#'s? for reference i saw about 77-78% @ 600 rwhp
I'm asking these questions because as a scientist, I don't get discouraged by mishaps or setbacks. I try to dig deep into the result, and figure out how I got there, and how to avoid the same outcome.
Last edited by The Alchemist; 02-19-2012 at 08:01 PM.
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02-20-2012, 08:34 AM
#8
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Too much timing, air was too cold, too much boost, and pump gas is why you lost the piston. Try E85 if you are wanting to run that much timing/boost. I never put cars over 12lbs/12deg in weather cooler than 60* on pump. I put my own stock shortblock at 14lb/14*/pump gas and got the same result as you in very similar conditions.
The AFR was probably not a big contributer and may have been helping it to actually live. The crack in the bore is probably a combination of too much heat from lack of rear cross over and the detonation.
The stock pistons are actually pretty tough at handling power, they just hate detonation. The bad thing is even with a scanner not showing knock when tuning, conditions will eventually come together and give you that result.
Toss another stock shortblock in it if you want and either back the tune off some, add meth, or E85.
The AFR was probably not a big contributer and may have been helping it to actually live. The crack in the bore is probably a combination of too much heat from lack of rear cross over and the detonation.
The stock pistons are actually pretty tough at handling power, they just hate detonation. The bad thing is even with a scanner not showing knock when tuning, conditions will eventually come together and give you that result.
Toss another stock shortblock in it if you want and either back the tune off some, add meth, or E85.
02-20-2012, 10:05 AM
#9
I concur!
Too much timing, air was too cold, too much boost, and pump gas is why you lost the piston. Try E85 if you are wanting to run that much timing/boost. I never put cars over 12lbs/12deg in weather cooler than 60* on pump. I put my own stock shortblock at 14lb/14*/pump gas and got the same result as you in very similar conditions.
The AFR was probably not a big contributer and may have been helping it to actually live. The crack in the bore is probably a combination of too much heat from lack of rear cross over and the detonation.
The stock pistons are actually pretty tough at handling power, they just hate detonation. The bad thing is even with a scanner not showing knock when tuning, conditions will eventually come together and give you that result.
Toss another stock shortblock in it if you want and either back the tune off some, add meth, or E85.
The AFR was probably not a big contributer and may have been helping it to actually live. The crack in the bore is probably a combination of too much heat from lack of rear cross over and the detonation.
The stock pistons are actually pretty tough at handling power, they just hate detonation. The bad thing is even with a scanner not showing knock when tuning, conditions will eventually come together and give you that result.
Toss another stock shortblock in it if you want and either back the tune off some, add meth, or E85.
02-20-2012, 08:26 PM
#11
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I would say go E85. I have a completely stock 5.3 and today was only the second day of driving but I drove 55 miles romping on it every chance I got. 20lbs of boost and ran like a raped ape. Mine has only been tuned at WOT so it ran crappy just cruising but at WOT my AFR was between 10.5 and 11.3. I am shocked I haven't ripped this thing apart already.
02-20-2012, 09:22 PM
#13
the rings butted under all the extra heat created by the boost that popped the ring land, I cant see how the piece of piston cracked the block,
on my stock ls2 short block I was seeing 15psi and at one point I had 19degs in it but I spray three nozzles of straight meth,
the only thing I can think that had enough force to crack the block was detonation, look at the upper rod bearing of that piston and see if the bearing looks deformed or going away from detonation trying to beat the bearing out
on my stock ls2 short block I was seeing 15psi and at one point I had 19degs in it but I spray three nozzles of straight meth,
the only thing I can think that had enough force to crack the block was detonation, look at the upper rod bearing of that piston and see if the bearing looks deformed or going away from detonation trying to beat the bearing out
