Cracked block and broken piston..
Thread Starter
Joined: Apr 2005
Posts: 1,014
Likes: 0
From: san marcos, TX
Cracked block and broken piston.. No damage to the heads. But cracked block and 2 broken pistons. No signs of detonation and fuel mix was 10.7:1. Looks like a stress riser from the factory drilled dot to mark forward caused the failure. #5 was broken and #7 had a crack that was about all the way through. Coolant in #5 cleaned the top of the piston pretty good though. 
New forged 346ci is on the way... 
Man I'm dirty...
New forged 346ci is on the way... Man I'm dirty...
Thread Starter
Joined: Apr 2005
Posts: 1,014
Likes: 0
From: san marcos, TX
Yeah, I new that. I already had a new block and all the parts for a new motor just sitting and waiting... It lasted a year though. Ever since I installed the blower, I've been gathering parts here and there when good deals came up for sale. Comming back bigger and better..
Motor details
346ci, Eagle LS1 6.125" rods, Diamond -8.6 dish pistons, stock crank, new LS6 block, ARP head bolts, custom ground Comp Cam 226/232 116LSA, Texas speed CNC LS6 stage 2.5 heads 2.04intake 1.575 exhaust valves, Will put me right at 9.5:1 compression...
My "to do list"
Pull old motor.
Build and install new motor. forged 346ci.
Port match new heads to intake.
Install new aluminum flywheel and Textrillia clutch.
Install bell housing blanket...
Install DTE tranny brace and left hardened output shaft.
Install hurst shifter.
Install Wolfe 6pt cage
Install Meth inj. system.
Install smaller pulley on blower..
Install line lock..
Install new stainless brake lines..
Relocate Bosch fuel pump.
Install Bilstein sport shocks.
Just a small list. I have a week off for christmas and I plan to have it up and running by then...
It lasted a year though. Ever since I installed the blower, I've been gathering parts here and there when good deals came up for sale. Comming back bigger and better..Motor details
346ci, Eagle LS1 6.125" rods, Diamond -8.6 dish pistons, stock crank, new LS6 block, ARP head bolts, custom ground Comp Cam 226/232 116LSA, Texas speed CNC LS6 stage 2.5 heads 2.04intake 1.575 exhaust valves, Will put me right at 9.5:1 compression...
My "to do list"
Pull old motor.
Build and install new motor. forged 346ci.
Port match new heads to intake.
Install new aluminum flywheel and Textrillia clutch.
Install bell housing blanket...
Install DTE tranny brace and left hardened output shaft.
Install hurst shifter.
Install Wolfe 6pt cage
Install Meth inj. system.
Install smaller pulley on blower..
Install line lock..
Install new stainless brake lines..
Relocate Bosch fuel pump.
Install Bilstein sport shocks.
Just a small list. I have a week off for christmas and I plan to have it up and running by then...
Last edited by chriswtx; Nov 26, 2006 at 09:43 PM.
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Same thing happened to me, broke that same little chunk of the piston off and cracked the block plus bent the connecting rod also - aluminum doesnt compress very well 
All it takes is a tiny bit of detonation at those power levels to bust the piston and there is a point even with no detonation they will just fail - I'm sure you were getting close to that point.
All it takes is a tiny bit of detonation at those power levels to bust the piston and there is a point even with no detonation they will just fail - I'm sure you were getting close to that point. Thread Starter
Joined: Apr 2005
Posts: 1,014
Likes: 0
From: san marcos, TX
Originally Posted by motorbuilt
man, you guys ripped that thing into a billion pieces now didnt you
Yeah, I was thinking the same thing. It's going to be lots of fun to put back together... 
remember also that stock rings are gapped a lot tighter too...coulda been ring butt. if that is your first one congrats on joining the HUGE club.....me and Mightymouse are the founding members i think
Thread Starter
Joined: Apr 2005
Posts: 1,014
Likes: 0
From: san marcos, TX
Originally Posted by cablebandit
remember also that stock rings are gapped a lot tighter too...coulda been ring butt. if that is your first one congrats on joining the HUGE club.....me and Mightymouse are the founding members i think
I've thought about that from day one of adding the blower. I have always been real careful not to run the car hard for more than 1/4 mile, always given it at least 30min cool down between runs, kept the mixture rich 10.7:1, timing low 14degs. On the street I never get on it more than a couple of gears for just a few seconds no more than 10sec for sure. And never back to back runs on the street. I think this was just a case of the stock cast pistons combustion chamber pressure limits...Too much power...
I think its just stress riser from the factory drilled dot to mark forward caused the failure. Its a very thin point in the piston at the ring land ... 
Thread Starter
Joined: Apr 2005
Posts: 1,014
Likes: 0
From: san marcos, TX
it took me about 10-11 hours so far. I could have just pulled the motor in about 4.5 hours, but I went ahead and pulled the rear end/rear suspension so I can add a hardened output shaft and DTE transmission brace... 
I just finished pulling apart the motor. All the rod and main bearings still look like new..
I just finished pulling apart the motor. All the rod and main bearings still look like new..
