Cracked Piston?
Thread Starter
Joined: Mar 2003
Posts: 8,319
Likes: 1
From: North Carolina
Cracked Piston? So, I have been concerned for some time on the motor. Last cam swap #5 and #7 were low on compression. I fly cut the pistons on the first cam after milling the heads and either assumed it weakened them, cracked something or had debris in the rings.
See the attached picture. Sorry I could not suck it off the bore scope, but I am pretty certain this is a cracked #7. Good news is the piece is there, so I believe I am going to park it and tear it down before I have collateral damage.
I just wanted to get some feedback from someone that has seen some failures.
Thanks.
See the attached picture. Sorry I could not suck it off the bore scope, but I am pretty certain this is a cracked #7. Good news is the piece is there, so I believe I am going to park it and tear it down before I have collateral damage.
I just wanted to get some feedback from someone that has seen some failures.
Thanks.
Thread Starter
Joined: Mar 2003
Posts: 8,319
Likes: 1
From: North Carolina
Here are some of the shots. Shiny edge is #3 and #5. Looks like #7 is toast...
On the bright side, while knocking on wood, hopefully because it is still together it saved my more damage to the heads.
Now to research/search and post for the next steps. Step 1 is to pull and assess, but now I have to figure out how I want to pull it. Then do I build or buy built already (leaning to buying, after I save a small fortune) and moving to a 383 which I think would suit the cam better anyway.
On the bright side, while knocking on wood, hopefully because it is still together it saved my more damage to the heads.
Now to research/search and post for the next steps. Step 1 is to pull and assess, but now I have to figure out how I want to pull it. Then do I build or buy built already (leaning to buying, after I save a small fortune) and moving to a 383 which I think would suit the cam better anyway.
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Looks like the piston cracked along the ring land. Next time be sure open the ring gap more on those hot cylinders so that doesn't happen. The ring heats up enough on that cylinder that there is no end gap, ring has to go someplace so it expands and cracks the piston. Been down this road myself.
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Verdad Gallardo Thread Starter
Joined: Mar 2003
Posts: 8,319
Likes: 1
From: North Carolina
Yes, I was just thinking about that. Clean it up with the stock crank, but I would do all the pistons, rods and what ever else is necessary to safely spin to 7000ish RPM. Would save a bunch of money.
At the same time, will I kick myself later for not spending the money the first time to just build a 383? Probably...I would like to get some low end back like when I had the 230/232 cam. I feel the cam I have now would do fairly well in a 383 and get some of that back.
At the same time, will I kick myself later for not spending the money the first time to just build a 383? Probably...I would like to get some low end back like when I had the 230/232 cam. I feel the cam I have now would do fairly well in a 383 and get some of that back.
On The Tree
Joined: Mar 2010
Posts: 124
Likes: 8
From: Navarre, FL
Yep, my number 7 was missing a piece and cracked on another side. 430whp LS6 on road course.
http://imgur.com/z3gs7F6
http://imgur.com/kTISTjB
http://imgur.com/z3gs7F6
http://imgur.com/kTISTjB
Thread Starter
Joined: Mar 2003
Posts: 8,319
Likes: 1
From: North Carolina
Awesome...
Last cam swap when I was low on compression and about 30% leak down I did not see any crack. So whatever it was has just gotten worse. Glad I decided to stick the bore scope in there, hopefully I got it soon enough to have better options.
What I am afraid started this (when my last setup was down about 12 HP or so) was my catch can setup. I got a lot of condensation in there, along with oil, and noticed it one day by the trail of smoke behind me. I cleaned that up and put on a breather to limp along since, waiting on my ultimate fate since there was nothing on the surface I could see that justified a "remove it now" situation.
Really not looking forward to tearing it out though. My days (and time) working on stuff like this is a thing of the past. Plus, my daughter is too little to just do it for me
Hopefully I can pull it out the top and be able to do all the head work outside. That will make life easier. Just need to research some options there. That is the last part of an F-body I have yet to remove completely.
Last cam swap when I was low on compression and about 30% leak down I did not see any crack. So whatever it was has just gotten worse. Glad I decided to stick the bore scope in there, hopefully I got it soon enough to have better options.
What I am afraid started this (when my last setup was down about 12 HP or so) was my catch can setup. I got a lot of condensation in there, along with oil, and noticed it one day by the trail of smoke behind me. I cleaned that up and put on a breather to limp along since, waiting on my ultimate fate since there was nothing on the surface I could see that justified a "remove it now" situation.
Really not looking forward to tearing it out though. My days (and time) working on stuff like this is a thing of the past. Plus, my daughter is too little to just do it for me
Hopefully I can pull it out the top and be able to do all the head work outside. That will make life easier. Just need to research some options there. That is the last part of an F-body I have yet to remove completely.
TECH Addict
Joined: Mar 2013
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Yep, my number 7 was missing a piece and cracked on another side. 430whp LS6 on road course.
http://imgur.com/z3gs7F6
http://imgur.com/kTISTjB
http://imgur.com/z3gs7F6
http://imgur.com/kTISTjB
TECH Addict
Joined: Mar 2013
Posts: 2,628
Likes: 30
Hate to say it but GM was trying to cut oil usage and I believe they purposely were setting the ring gap on the tight side.................you see the results. Of course they would never admit to such a thing. I seen so many broken like this even on a stock tune, but after a "TUNE" look out number 7 is just waiting for a single WOT run to pop the ring lands off. Mine was "TUNED", it ran awesome but the piston top went right out the exhaust!
Last edited by RockinWs6; Apr 16, 2017 at 07:03 AM.
TECH Addict
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I have no idea why people pull um out the bottom. It so easy out the top its just stupid. I pull the engine and trans together because of those bastard torxhead trans bolts. Be sure you use a hand impact driver with the proper bit or your life will be miserable for a few days.
Thread Starter
Joined: Mar 2003
Posts: 8,319
Likes: 1
From: North Carolina
What do you recommend to pull out the top? I was planning to pull the hood, radiator and accessories along with the intake. I was going to look and see, but I recall a while ago a lifting plate for the valley to pull it.
I was going to try to block up the tranny and see if I could leave it. What is the weight of the long block and tranny separately? I want to make sure I borrow something that can handle the weight.
I have been out of the game for so long, about 8 years. Leaning towards rebuilding this with new rods and pistons and leaving larger cubes for a later date. With this setup and no loss of compression I should remain in the 480 HP range even with cats back on and no cutout. Main reason for a 383 was get that low end back and tame the idle more with this larger cam, but I also posted about finding better tires - what's the point if I am not planning on any runs at the track?
My last cam was down 12 HP (was trying to find the graphs) and the entire curve was shifted low. The new cam got me back up about 8 HP but that was also about 12 months later I think so I don't know the comparative health. I could only assume it was even worse then. So apples to apples I would have expected this new setup to approach 490/450, but have since added cats and ditched the cutout which will more than likely put the top end back to 480ish of the old cam.
I was going to try to block up the tranny and see if I could leave it. What is the weight of the long block and tranny separately? I want to make sure I borrow something that can handle the weight.
I have been out of the game for so long, about 8 years. Leaning towards rebuilding this with new rods and pistons and leaving larger cubes for a later date. With this setup and no loss of compression I should remain in the 480 HP range even with cats back on and no cutout. Main reason for a 383 was get that low end back and tame the idle more with this larger cam, but I also posted about finding better tires - what's the point if I am not planning on any runs at the track?
My last cam was down 12 HP (was trying to find the graphs) and the entire curve was shifted low. The new cam got me back up about 8 HP but that was also about 12 months later I think so I don't know the comparative health. I could only assume it was even worse then. So apples to apples I would have expected this new setup to approach 490/450, but have since added cats and ditched the cutout which will more than likely put the top end back to 480ish of the old cam.
I've pulled through the top. It's stupid. You have to essentially remove everything to take it out of the top. Manifold. Headers. All the accessories. I even had the car up 28" in the air. The trans was not coming with it in one piece. You need to be able to rotate the engine to get it to clear the firewall. Even on a cherry picker with an adjustable engine hoist and 2 people it took a lot to get it out of the top.
It takes like 45 mins to pull it from the bottom.
Bottom is... 2 brake lines, 6 k-member bolts, 4 bolts for the trans crossmember, heater hose, and radiator hose, and unbolt the exhaust from the headers... and unplug the wiring harness from the firewall and PCM. You can unbolt your A/C from the engine and leave it in the car. Finally, you unbolt the shock towers from the body and the upper a-arms come with the k-member.
Then you use the cherry picker to pick it up by the radiator support beam. And you wheel the k-member out with the trans, engine, headers all connected and the front suspension and brakes in tact and connected to the spindle.
Then you can work on everything without any obstruction. If you have a tubular k-member... you can actually remove the oil pan and get to the bottom end without ever removing the motor from the k-member. But for you, you'll want to take everything off and set aside.
I would do the 383.
It takes like 45 mins to pull it from the bottom.
Bottom is... 2 brake lines, 6 k-member bolts, 4 bolts for the trans crossmember, heater hose, and radiator hose, and unbolt the exhaust from the headers... and unplug the wiring harness from the firewall and PCM. You can unbolt your A/C from the engine and leave it in the car. Finally, you unbolt the shock towers from the body and the upper a-arms come with the k-member.
Then you use the cherry picker to pick it up by the radiator support beam. And you wheel the k-member out with the trans, engine, headers all connected and the front suspension and brakes in tact and connected to the spindle.
Then you can work on everything without any obstruction. If you have a tubular k-member... you can actually remove the oil pan and get to the bottom end without ever removing the motor from the k-member. But for you, you'll want to take everything off and set aside.
I would do the 383.
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Joined: Mar 2013
Posts: 2,628
Likes: 30
What do you recommend to pull out the top? I was planning to pull the hood, radiator and accessories along with the intake. I was going to look and see, but I recall a while ago a lifting plate for the valley to pull it.
I was going to try to block up the tranny and see if I could leave it. What is the weight of the long block and tranny separately? I want to make sure I borrow something that can handle the weight.
I have been out of the game for so long, about 8 years. Leaning towards rebuilding this with new rods and pistons and leaving larger cubes for a later date. With this setup and no loss of compression I should remain in the 480 HP range even with cats back on and no cutout. Main reason for a 383 was get that low end back and tame the idle more with this larger cam, but I also posted about finding better tires - what's the point if I am not planning on any runs at the track?
My last cam was down 12 HP (was trying to find the graphs) and the entire curve was shifted low. The new cam got me back up about 8 HP but that was also about 12 months later I think so I don't know the comparative health. I could only assume it was even worse then. So apples to apples I would have expected this new setup to approach 490/450, but have since added cats and ditched the cutout which will more than likely put the top end back to 480ish of the old cam.
I was going to try to block up the tranny and see if I could leave it. What is the weight of the long block and tranny separately? I want to make sure I borrow something that can handle the weight.
I have been out of the game for so long, about 8 years. Leaning towards rebuilding this with new rods and pistons and leaving larger cubes for a later date. With this setup and no loss of compression I should remain in the 480 HP range even with cats back on and no cutout. Main reason for a 383 was get that low end back and tame the idle more with this larger cam, but I also posted about finding better tires - what's the point if I am not planning on any runs at the track?
My last cam was down 12 HP (was trying to find the graphs) and the entire curve was shifted low. The new cam got me back up about 8 HP but that was also about 12 months later I think so I don't know the comparative health. I could only assume it was even worse then. So apples to apples I would have expected this new setup to approach 490/450, but have since added cats and ditched the cutout which will more than likely put the top end back to 480ish of the old cam.
Thread Starter
Joined: Mar 2003
Posts: 8,319
Likes: 1
From: North Carolina
I am trying the top. I already have most pulled off, at least what I could working for an hour this morning. No AC on the car so the front is wide open. Just need to pull accessories, drain oil, disconnect electrical plugs left and try to break the transmission. I am going to attempt to leave it. I don't want to screw with the torque arm, I hate it lol
Question I have is do I break the tranny loose from the bellhousing or bellhousing from motor?
Question I have is do I break the tranny loose from the bellhousing or bellhousing from motor?
Last edited by WS6FirebirdTA00; Apr 16, 2017 at 06:48 PM.
Thread Starter
Joined: Mar 2003
Posts: 8,319
Likes: 1
From: North Carolina
They came out OK when I did tranny work. We will see.
The more time it takes the longer I can save
The more time it takes the longer I can save
Last edited by WS6FirebirdTA00; Apr 16, 2017 at 06:48 PM.