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Groove on top of piston?

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Old Nov 6, 2012 | 06:25 PM
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Default Groove on top of piston?

Guys, I am currently rebuilding an LS1 & while I was cleaning the pistons up I noticed a small groove on the top of some of them(#2, 4, & 5..so far, havent cleaned the rest). Below I will post a picture of it with a circle around the groove, hopefully everyone can see it.

My question is, what is the groove? Is it going to be a problem? Is it caused by something that could damage the engine?

While I am rebuilding the bottom end, I am installing an MS3 cam, ported LS6 heads, LS6 intake, & American Racing LTs.

Well, onto the pic. Let me know something guys, Thanks in advance.



Brenton
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Old Nov 6, 2012 | 06:30 PM
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Pretty sure theres been some piston to valve contact going on. Was the motor already cammed before you started rebuilding it? Incorrect valve springs/valve float.
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Old Nov 6, 2012 | 06:35 PM
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agreed ^^^
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Old Nov 6, 2012 | 07:23 PM
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no, the engine was stock before the rebuild. Bought the engine/transmission/etc from a buddy out of his wrecked z28. it only had 63k miles on it when he wrecked it.

Will it be okay to use the pistons since ill be going with new heads, valves, etc? or am I pretty much fucked?
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Old Nov 6, 2012 | 07:25 PM
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Originally Posted by Coonass350
no, the engine was stock before the rebuild. Bought the engine/transmission/etc from a buddy out of his wrecked z28. it only had 63k miles on it when he wrecked it.

Will it be okay to use the pistons since ill be going with new heads, valves, etc? or am I pretty much fucked?
The piston is probably ok to use, but make sure you put some good valvesprings in with that cam or that motor won't last long. It's a bit strange to me that a stock cammed LS1 was having piston to valve contact with only 63K on it....odd. Doesn't add up.
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Old Nov 6, 2012 | 07:31 PM
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NightmareTA, I agree.. it is odd that the stock cam was having problems with piston to valve contact. Maybe it was due to a missed shift or a 3rd gear to 2nd gear wot shift on accident. I dont know how my friend drove it really.

When I go back in with the MS3 cam I will be going with some PRC .650" valve springs so that should be sufficient. Ill be using stock rockers with the Comp Cam Trunion Upgrade, in case any of this matters.
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Old Nov 6, 2012 | 08:27 PM
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any other opinions? would like some more nods to go ahead and use the pistons.
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Old Nov 6, 2012 | 08:37 PM
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Piston looks okay to me. I'd be more worried about bent valves.
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Old Nov 6, 2012 | 09:55 PM
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alright cool. Im not worried about the valves because Ill be going with a different head, valves, springs, etc entirely.

Ill go ahead and finish cleaning the others and get ready to install them. Thanks guys.
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Old Nov 6, 2012 | 11:11 PM
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Originally Posted by NightmareTA
The piston is probably ok to use, but make sure you put some good valvesprings in with that cam or that motor won't last long. It's a bit strange to me that a stock cammed LS1 was having piston to valve contact with only 63K on it....odd. Doesn't add up.
I bought one with less miles than that and every piston had valve marks on it. All it takes is one missed gear.
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Old Nov 7, 2012 | 08:42 AM
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Originally Posted by LS1MCSS
I bought one with less miles than that and every piston had valve marks on it. All it takes is one missed gear.
Did you go ahead & use the pistons?
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Old Nov 7, 2012 | 09:11 AM
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If it makes you feel any better, I had similar valve marks on every single piston in my turbo 5.3. Had to rip it apart and replace a piston with a cracked ringland, which is how I originally noticed them. Slapped it back together with the fresh piston and just took it for a rip ride last night. Runs great, and that's with 11 PSI and 563 rwhp. I'm sure your pistons will last a long long time on an N/A motor.
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Old Nov 7, 2012 | 12:05 PM
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Okay guys now I have another question. On the #6 piston I noticed a little mark/slash on the side of it. Below is a picture. Is this something I should worry about? I can feel it just slightly when running my finger nail around the piston.


Last edited by Coonass350; Nov 7, 2012 at 09:46 PM.
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Old Nov 7, 2012 | 12:24 PM
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That little groove in the first pic is just fine. I accidentally dropped it into 2nd gear at 80+mph in my 2000 C5 when is was bone stock at 34k miles on the odometer. When disassembling the motor, every piston had fairly large grooves from the intake and exhaust valves, most of the valves and pushrods were bent, if not all. Some pushrods were rainbow shaped. I intially thought the pistons were junk. After having them inspected, they were all fine, no cracks. Just had to flycut reliefs in them and clean them up. Those pistons have been working perfectly fine for 9k miles at 430whp.
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Old Nov 7, 2012 | 01:11 PM
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Originally Posted by R6cowboy
That little groove in the first pic is just fine. I accidentally dropped it into 2nd gear at 80+mph in my 2000 C5 when is was bone stock at 34k miles on the odometer. When disassembling the motor, every piston had fairly large grooves from the intake and exhaust valves, most of the valves and pushrods were bent, if not all. Some pushrods were rainbow shaped. I intially thought the pistons were junk. After having them inspected, they were all fine, no cracks. Just had to flycut reliefs in them and clean them up. Those pistons have been working perfectly fine for 9k miles at 430whp.
Alright cool, glad to hear the groove on top wont cause a problem. Any idea on the 2nd pic? the groove/mark on the side.
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Old Nov 7, 2012 | 05:21 PM
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Originally Posted by Coonass350
Alright cool, glad to hear the groove on top wont cause a problem. Any idea on the 2nd pic? the groove/mark on the side.
that's kinda iffy. as cheap as you can find a stock piston I might just find another... are you using the original block it came out of? any evidence of the cylinder roughed up in that area?
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Old Nov 7, 2012 | 05:56 PM
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Originally Posted by AutomagicLS1
that's kinda iffy. as cheap as you can find a stock piston I might just find another... are you using the original block it came out of? any evidence of the cylinder roughed up in that area?
How much does a stock piston usually run? and if I got another stock piston would it be a direct replacement? I mean would any machine work or block work need to be done before installing it?

Yes this is the original block it came out of. I havent checked the cylinder yet for any roughed up spots but will in just a few minutes.
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Old Nov 7, 2012 | 07:00 PM
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I just went out and looked that cylinder over. There is a very very faint mark on one side. I slid the piston in just to see about where the mark was and they are in the same spot. So I dont know what to do. Want to use the piston but dont want it to cause a problem. What is the worst that could happen?

I mean when I slide the piston in, it didnt seem to be rough feeling. The mark on the piston is faint and can barely tell that its there with your fingernail & the same with the little mark on the cylinder.

Before my friend wrecked the car he didnt have trouble with the engine, it ran strong.
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Old Nov 7, 2012 | 09:47 PM
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anybody else want to comment on the 2nd pic? okay to run it?
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Old Nov 7, 2012 | 09:51 PM
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Originally Posted by LS1MCSS
I bought one with less miles than that and every piston had valve marks on it. All it takes is one missed gear.
Truth.
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