Broken #2 piston-Why? (pic)
Race Director
Joined: Oct 2000
Posts: 15,009
Likes: 79
From: central FL, near the beach.
A cure might be as simple as changing the plug to 1 heat range cooler on the #2 cyl. and it costs only $2 to try!
a red hot electrode will cause preignition and wack a piston to death.
.
reminds me of a motor that wipes a cam lobe. then it wipes the same lobe again. How many times do u yell "cheap cam"?
a red hot electrode will cause preignition and wack a piston to death.
.
reminds me of a motor that wipes a cam lobe. then it wipes the same lobe again. How many times do u yell "cheap cam"?
Last edited by Matt Gruber; Jun 8, 2007 at 07:55 AM.
Safety Car
Joined: Mar 2007
Posts: 3,652
Likes: 49
From: Bridgewater nj
Look At The Ring Gap
Looking at the ring gap from the pic on a cold engine you can tell it is very tight. you should have atleast .027 if not more. unless the ring is cracked elsewhere and is closing the gap in the pic. That gap is barely .015. go back and check all the bores for scratches and ring gaps
Thread Starter
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Engines back from the builder with all new forged Weisco pistons.Now the process of painting,dropping in the engine and installing all that (pita) shielding begins.Vrrrmmm
Thread Starter
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Oh man I'm sorry to hear your block is cracked that bad news for sure.Did you have hyper pistons in yours? Are you going to fix your block do the numbers match the car?
Burning Brakes
Joined: Feb 2007
Posts: 779
Likes: 0
From: San Bruno California
Yeh, It's a numbers matching car. Found out the piston is .030 over. Not sure what kind of piston is in there. The odometer says 75,000, but some past owner must have rebuilt it before. I don't think it would have come .030 over from the factory, would it? Right now i'm torn between the crate motor but like the stock clean look. Mechanics at work says that I can sleeve the cylinder. Not a big deal, but now finding out that it's bored once, I have to see what my options are. I really don't want to spend alot of money. I can buy a short block and put aside my no. matching motor and still use all my other parts to put back together. As soon as I hear a noise I was smoking out the rear. So after opening it up and seeing the cracked cyl. I new it cracked when I heard the noise. Mine was no. 4 cyl.
Walls are scored. Tony
Walls are scored. Tony
Le Mans Master
Joined: Jan 2006
Posts: 6,504
Likes: 139
From: Butler Pa
Found out the piston is .030 over. Not sure what kind of piston is in there. The odometer says 75,000, but some past owner must have rebuilt it before. I don't think it would have come .030 over from the factory, would it? ...
Mechanics at work says that I can sleeve the cylinder. Not a big deal...
So after opening it up and seeing the cracked cyl. I new it cracked when I heard the noise. Mine was no. 4 cyl.
Walls are scored. Tony
Mechanics at work says that I can sleeve the cylinder. Not a big deal...
So after opening it up and seeing the cracked cyl. I new it cracked when I heard the noise. Mine was no. 4 cyl.
Walls are scored. Tony
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Thread Starter
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Yeh, It's a numbers matching car. Found out the piston is .030 over. Not sure what kind of piston is in there. The odometer says 75,000, but some past owner must have rebuilt it before. I don't think it would have come .030 over from the factory, would it? Right now i'm torn between the crate motor but like the stock clean look. Mechanics at work says that I can sleeve the cylinder. Not a big deal, but now finding out that it's bored once, I have to see what my options are. I really don't want to spend alot of money. I can buy a short block and put aside my no. matching motor and still use all my other parts to put back together. As soon as I hear a noise I was smoking out the rear. So after opening it up and seeing the cracked cyl. I new it cracked when I heard the noise. Mine was no. 4 cyl.
Walls are scored. Tony
Walls are scored. Tony
Worst I've seen on the street.Cost was about 3K to save it.Personally and if you want to have fun with the car I would opt for the crate motor.Of course save the old block.
Safety Car
Joined: Apr 2005
Posts: 3,624
Likes: 431
From: Dale City VA
I have seen many KB hyper pistons broken like the one in your pic come through my shop. As others have said here - every time it was insufficient top ring gap or detonation or both that caused it.
Personally I would cut back the compression ratio a bit. Depending on your camshaft, 10.5 SCR may be a bit steep for pump gas with iron heads. A high dollar set of Weisco's may live longer but your problem could still be there. And don't think you can't hurt an expensive piston just because it is forged. They will live longer under abuse but not forever.
Will
Personally I would cut back the compression ratio a bit. Depending on your camshaft, 10.5 SCR may be a bit steep for pump gas with iron heads. A high dollar set of Weisco's may live longer but your problem could still be there. And don't think you can't hurt an expensive piston just because it is forged. They will live longer under abuse but not forever.
Will
Burning Brakes
Joined: Feb 2007
Posts: 779
Likes: 0
From: San Bruno California
I've only have the passenger side head removed and all the piston reads .030. So I'm assuming their all .030 over. I thinking rather than rebuild the numbers motor, I'll set it asside and do one of two things: !) find another block and rebuild that or drop a crate motor or maybe buying a short or long block. Which is the cheapest route to take? I kind of don't want to rebuild the original motor and have something go wrong with it again.
Some members say that rebuilding a motor might excede the cost of a crate motor when everything is said and done.
What ever I put in, I want it to be alittle lopy and have some umph.
Some members say that rebuilding a motor might excede the cost of a crate motor when everything is said and done.
What ever I put in, I want it to be alittle lopy and have some umph.
Melting Slicks
Joined: Mar 2002
Posts: 2,164
Likes: 7
From: Beringen
I have seen many KB hyper pistons broken like the one in your pic come through my shop. As others have said here - every time it was insufficient top ring gap or detonation or both that caused it.
Personally I would cut back the compression ratio a bit. Depending on your camshaft, 10.5 SCR may be a bit steep for pump gas with iron heads. A high dollar set of Weisco's may live longer but your problem could still be there. And don't think you can't hurt an expensive piston just because it is forged. They will live longer under abuse but not forever.
Will
Personally I would cut back the compression ratio a bit. Depending on your camshaft, 10.5 SCR may be a bit steep for pump gas with iron heads. A high dollar set of Weisco's may live longer but your problem could still be there. And don't think you can't hurt an expensive piston just because it is forged. They will live longer under abuse but not forever.
Will
