Boosted LS7 Carnage
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TECH Enthusiast
Joined: Jan 2010
Posts: 544
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From: Irvine, CA.
Boosted LS7 Carnage 2007 C6 Z06 Corvette
Stock bottom end
BTR cam, springs, pushrods, CHE rockers
Kooks long tubes, B&B Bullet exhaust
A&A Super Charger, 8 rib conversion
WCCH CNC ported heads
ACT dual disc clutch
Boost a pump
Pulleys for 9 psi.
12 degrees of timing on the dyno and all hell broke loose!
Cylinders 5 and 7 broke the top ring lands at the 10 o-clock position. Both cylinder walls also cracked blowing coolant everywhere.
Stock bottom end
BTR cam, springs, pushrods, CHE rockers
Kooks long tubes, B&B Bullet exhaust
A&A Super Charger, 8 rib conversion
WCCH CNC ported heads
ACT dual disc clutch
Boost a pump
Pulleys for 9 psi.
12 degrees of timing on the dyno and all hell broke loose!
Cylinders 5 and 7 broke the top ring lands at the 10 o-clock position. Both cylinder walls also cracked blowing coolant everywhere.
Interesting how the pistons broke in the same spot. I assume that's where the gaps were? Do you know what the gap was?
Sorry for your loss. Glad it didn't happen at speed.
Sorry for your loss. Glad it didn't happen at speed.
Staging Lane
Joined: Jul 2012
Posts: 86
Likes: 0
From: Detroit, MI
The rings move in the bore, I highly doubt the gaps would just happen to line up in the exact same place. That is probably just the weakest part of the piston, or the area that runs hottest on the piston crown, causing knock.
OP were you running 93?
OP were you running 93?
Restricted User
Joined: Mar 2014
Posts: 7,192
Likes: 109
From: Ohio
If the ring gaps were unchanged, I would vote ring gaps as well.
Everytime I see someone break an LS7 on less power than I've made a hundred times on a junkyard engine, I have to believe I made the right choice... I couldn't afford what just happened here.
Everytime I see someone break an LS7 on less power than I've made a hundred times on a junkyard engine, I have to believe I made the right choice... I couldn't afford what just happened here.
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I would agree with that. However, if this was a new build, maybe all the ring gaps were left in that position and then it blew up. All the Pistons and everything else looks clean which leads me to believe this is a fresh engine.
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Thread Starter
TECH Enthusiast
Joined: Jan 2010
Posts: 544
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From: Irvine, CA.
These pistons and rings are stock GM LS7. Car has 35K miles. This was not a new build. The car came to me with the A&A kit on it. Installed by another shop about 2 years ago. I sent the heads out and changed the cam and put on an 8 rib set up.
Made 5 dyno pulls. 660 HP/650TQ. No signs of any detonation. Added 1 more degree of timing. At about 5600 the tuner thought something didn't feel right so he shut it down. A few minutes later he started it back up and it blew coolant out the left side exhaust.
Made 5 dyno pulls. 660 HP/650TQ. No signs of any detonation. Added 1 more degree of timing. At about 5600 the tuner thought something didn't feel right so he shut it down. A few minutes later he started it back up and it blew coolant out the left side exhaust.
Was the valve to piston clearance checked? on a cast piston it doesn't take but a slight touch and things go wrong
I know some guys run timing that low, but I sometimes wonder if its enough
to start the burn so you dont leave excess fuel as it compresses the mixture
We found this years ago on a gen 1 engine-I am still wrapping my head around timing on gen 3 engines, how diff they are in tuning, lol
I know some guys run timing that low, but I sometimes wonder if its enough
to start the burn so you dont leave excess fuel as it compresses the mixture
We found this years ago on a gen 1 engine-I am still wrapping my head around timing on gen 3 engines, how diff they are in tuning, lol
Thread Starter
TECH Enthusiast
Joined: Jan 2010
Posts: 544
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From: Irvine, CA.
Put together a replacement engine.
New GM LS7 block
Callies Dragon Slayer crank
Callies Ultra H beam rods
Wiseco 18cc dish pistons
Clevite bearings
Durabond cam bearings
Fully balanced
New GM LS7 block
Callies Dragon Slayer crank
Callies Ultra H beam rods
Wiseco 18cc dish pistons
Clevite bearings
Durabond cam bearings
Fully balanced
