Skuff marks on psiton skirts-please look
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Skuff marks on piston skirts-please look I got these pistons from a forum member here. I was told they had some scuff marks on the skirts but it was nothing to worry to about. The pistons look brand new and were apparantly just in the car for a short period when the owner decided to go bigger so the parts that could be sold where sold. The motor was put togehter by a well respected sponser-I have contacted the seller but I have yet to hear back from them. Here are the pics of the skirts-I'll post some more tonight-they look worse in person.The marks are only on 1 side of the skirt. I was told not to use by my engine builder-he said the motor would be noisy until it got warm-what are your thoughts?
Last edited by eb02z06; Aug 21, 2006 at 11:05 AM.
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Those scuff marks are perpendicular to the pin which means the piston skirt
expanded and wasn't clearanced properly to the cylinder bore, or poor oil/
cooling system control was the original cause in the last motor.
That could be the major thrust side; check the orientation for forward facing
marks and if the pistons are numbered you can figure it out pretty quick.
From what I see, the piston should be fine. I would check the top ring lands
and make sure they're not scuffed. Have the pistons fluxed to rule out hair
line cracks.
I wouldn't say they're totally garbage yet. There might be some surface
finshing required to protect the metal and heat transfer characteristics.
The biggest concern would be warping of the piston from excessive heat.
In that case, they're probably not worth the risk of trying.
expanded and wasn't clearanced properly to the cylinder bore, or poor oil/
cooling system control was the original cause in the last motor.
That could be the major thrust side; check the orientation for forward facing
marks and if the pistons are numbered you can figure it out pretty quick.
From what I see, the piston should be fine. I would check the top ring lands
and make sure they're not scuffed. Have the pistons fluxed to rule out hair
line cracks.
I wouldn't say they're totally garbage yet. There might be some surface
finshing required to protect the metal and heat transfer characteristics.
The biggest concern would be warping of the piston from excessive heat.
In that case, they're probably not worth the risk of trying.
Last edited by Adrenaline_Z; Aug 21, 2006 at 12:23 PM.
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The damage is only on the skirt and not on any of the ringlands. It doesn't feel that rought to the touch but i'm not expert. I wish i could tell you why the torque is so low-my timing is very conservative, my compression is lower than stock and i'm running the factory cats-I think the factory cats are the main reason.
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You need to mic the pistons to make sure the skirts are not collapsed. Those look like crap, something was not right, clearances or dirty assembly. I can pull short skirt pistons out of our road race 350's and dirt modified 400's that have 2 full seasons on them with little or no scuffing.
How easily do the lines catch your fingernail?
How easily do the lines catch your fingernail?
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Mmmm this is no good Jason from Thunder sold these and said they are fine. I've pm'd him twice and no answer. Might have to put this in the feedback section if he doesn't reply.
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You can clean them up and have them coated all you want but the trouble will be the ovality of the piston is probably compromised. A piston is not round. That piston was not happy. When you measure the piston for clearance they are measured 90 degrees from the pin. In this case the measurement maybe too small to what you really need and you could be a little tight.
Doesn't really strike me as that bad I have seen a lot of factory pistons come out with simular marks so my only thing to tell you to be sure is have them checked by a qualified machine shop and you might try a couple to make sure the one your using isn't just trying to sell you some extra parts etc... Good luck!
Those pistons don't look very good. It looks like some excessive loading on the thrust side, which is where you would expect it. I wonder if it could be from high loads and low temperatures (not letting the car warm up). They may be fine coming out of an engine, but I would not put them back in. Remember that they will run against the bores in your block, so you put your block at risk as well. For the price of pistons I would have bought new.
I don't think there's anything a machine shop can do for you either. The skirt form isn't anything they will be able to reproduce, and any material removal will only increase the piston to bore clearances.
I don't think there's anything a machine shop can do for you either. The skirt form isn't anything they will be able to reproduce, and any material removal will only increase the piston to bore clearances.
I'm curious as to the setup the previous owner had them in. Not knowing much about the old setup the first thing that comes to mind is a bad rod length for the stroke. Too great of a rod angularity; which like these guys said previously loaded up the thrust side and bound it against the wall. If the bore clearances were too tight it would have issues most of the way around the skirt, and if the piston was out of round it would show wear on two different spots 180 out. Which leaves me with excessive rod angularity?
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The piston is naturally oval, it expands perpendicular to the pin. Your rod
theory might have value, but even the shortest rod combo wont do that to a piston.
That was a bad clearance job, or cooling/oil failure IMO. I don't think we'll
ever know the true cause.
theory might have value, but even the shortest rod combo wont do that to a piston.
That was a bad clearance job, or cooling/oil failure IMO. I don't think we'll
ever know the true cause.
You know my thoughts, not worth the risk. Hey Arun, I have 383 dished setup here, the pistons and rods are used (perfect condition), but a brand new eagle 4". I even have a nice LS6 block here ready to rock. We could even substitute the rods (I think you have some 6.125's) Can get that done in no time.
