Mrgoodwrench3

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.

yenkomike

iTrader: (2)

how many miles . looks like the ring gaps were to tight .damn shame sorry about your luck.

69-chvl

iTrader: (11)

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.

NoorJ

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?

svslow

This was only on 9psi and 12 degrees?

JoeNova

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.

ddnspider

iTrader: (26)

Any knock on the dyno run? What was the AFR during the pull?

69-chvl

iTrader: (11)

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.

truckdoug

iTrader: (25)

dang, bummer

Mrgoodwrench3

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.

Busa_rob

iTrader: (1)

That's textbook tight ring gap right there, not detonation.

sbcgenII

iTrader: (1)

Detonation.

hellbents10

iTrader: (10)

Stock bottom LS7 and boost is a gamble at best on pump gas. You can run them super fat with no timing and hope for the best is all.

forcd ind

iTrader: (7)

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

Mrgoodwrench3

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

slocaddy

Well that's one way to fix it lol!

stevieturbo

Is it still not a risk with the LS7 block ? Would they not have very thin liners compared to some other options ?

sbcgenII

iTrader: (1)

Maybe he installed some sleeves???

stevieturbo

Maybe he did...but he doesnt say he did.

Krom

wouldn't it have been cheaper, to build a stronger engine, by having the existing block sleeved???