LS3 Rod Failure
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Joined: Feb 2008
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From: Grasonville Maryland
Ran practice session 20 minutes just to get a heat in motor less then 4k . Missed qualifying next day changing rear gears. Get to grid for race in last. Ran about 2 miles heating brakes up maybe 6k and poof not even a boom pretty uneventful engine died. The only thing that i did that factory did not recommended was i had 112 race gas and mixed with 100 octane. Used to run high compression iron block and this was the fuel leftover. At this point i'm just trying to figure out if i screwed it up or there is a parts issue. I have had others more versed in engine building and they think parts issue. 750 holley pro system carb electric fuel pump 6psi steady 5 stage barnes. Motor was tuned on dyno and broke in per chevy on dyno.
Last edited by SmokeyD; Oct 5, 2019 at 11:10 AM.
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Joined: Feb 2008
Posts: 95
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From: Grasonville Maryland
This is my thinking also. Now i just have to figure out what the more to it is. I have ran out of skill trying to figure out what went wrong. Redoing another LS3 and do not want to repeat.
Le Mans Master
Joined: Dec 2005
Posts: 6,999
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From: Southeast TX
There's nothing inherently weak about a stock bottom end LS3. The LSA supercharged engine (580 hp) uses cast pistons and powdered metal con rods....but a forged steel crank. And it came with a warranty and was eligible for an extended warranty in Gen 5 ZL1 Camaros and Caddy CTS-V's. Stock LS3 cast cranks have a proven record well north of 750rwhp. I know this little bit of info doesn't point to the reason for failure.
Hell, if I was class limited to a basically stock LS3 with a really mild camshaft, I'd look for an LS3 (or even L99} takeout. At that power level, the damn things ought to be very reliable.
Hell, if I was class limited to a basically stock LS3 with a really mild camshaft, I'd look for an LS3 (or even L99} takeout. At that power level, the damn things ought to be very reliable.
Pro
Joined: Sep 2017
Posts: 675
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From: Green Oak Township, Michigan
There are Race Motors......and there are RACE MOTORS.......Dont cheap out on pistons. Put a good forged piston in there like Diamond Pistons with a good coating on the skirts. and some light weight pins. Your crank will be fine. Powder Metal rods......yuck...Maybe alright for grandmas pickup truck..Just my opinion. Its your money. It had to be the rod breaking, because I dont see that much wrong with that bearing. A little scuffed up but so what. Hell, we would throw that back in and make next round!!!! Did some crazy things back in the day.. It was a lot more fun before cubic money set in. Good Luck to you....
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Joined: Feb 2008
Posts: 95
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From: Grasonville Maryland
There are Race Motors......and there are RACE MOTORS.......Dont cheap out on pistons. Put a good forged piston in there like Diamond Pistons with a good coating on the skirts. and some light weight pins. Your crank will be fine. Powder Metal rods......yuck...Maybe alright for grandmas pickup truck..Just my opinion. Its your money. It had to be the rod breaking, because I dont see that much wrong with that bearing. A little scuffed up but so what. Hell, we would throw that back in and make next round!!!! Did some crazy things back in the day.. It was a lot more fun before cubic money set in. Good Luck to you....
Race Director
Joined: Sep 2007
Posts: 16,557
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From: Peoria/Phoenix AZ
C6 of Year Finalist (performance mods) 2019
This was the result of a dropped valve from an over-rev. You can see a partial piston and rings along with rod caps in odd positions on the second journal.
Bending until the piston was gone and then breaking as the pin broke through the cylinder wall.
Salvaged the crank and a couple rods to make a TP holder for the shop bath.
I fully believe your rod failure was a manufacturing defect. If mine bent and twisted before it broke (above 7000 rpm) and I can't break any of the others by hand, I'd be getting some structural materials testing done on that one and all the others. If you can show proof of a manufacturing error, GM owes you a new engine plus all labor involved.
The powdered metal process allows for the cracked rod technology, which controls fit and sizing to closer tolerances. However, the cracking is done in a very controlled manner.
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Thread Starter
Advanced
Joined: Feb 2008
Posts: 95
Likes: 2
From: Grasonville Maryland
This was the result of a dropped valve from an over-rev. You can see a partial piston and rings along with rod caps in odd positions on the second journal.
Bending until the piston was gone and then breaking as the pin broke through the cylinder wall.
Salvaged the crank and a couple rods to make a TP holder for the shop bath.
I fully believe your rod failure was a manufacturing defect. If mine bent and twisted before it broke (above 7000 rpm) and I can't break any of the others by hand, I'd be getting some structural materials testing done on that one and all the others. If you can show proof of a manufacturing error, GM owes you a new engine plus all labor involved.
The powdered metal process allows for the cracked rod technology, which controls fit and sizing to closer tolerances. However, the cracking is done in a very controlled manner.
Race Director
Joined: Sep 2007
Posts: 16,557
Likes: 2,106
From: Peoria/Phoenix AZ
C6 of Year Finalist (performance mods) 2019
Ouch! this is what i would expect from an operator error. My rods were a clean snap. I'm sending rods to GM for a look but i expect to be told pound sand. What kind of racing did you do this engine in? What rpm? I have a matching crank if you want to get fancy in the shop bath.
Actually, the crank only has a few dings on the counterbalances. All the bearing surfaces are perfect.
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Joined: Feb 2008
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From: Grasonville Maryland
Got a response back from GM. They said the motor was over revved and destroyed a piston pound sand. No that was some funny s... as the motor was still being broke in. I guess the lesson learned is GM crate motors built for racing are not really built to race.