View Full Version : Piston damage
So here is the offending piston out of the truck
http://media6.dropshots.com/photos/629366/20101031/b_210015.jpg
http://media7.dropshots.com/photos/629366/20101031/b_210034.jpg
Is this normal wear on a piston skirt??
http://media7.dropshots.com/photos/629366/20101031/b_210046.jpg
Other side looks fine
http://media8.dropshots.com/photos/629366/20101031/b_210101.jpg
kota360
10-31-2010, 08:52 PM
What side is all of the wear on? The outside, when the piston is going up and down in the bore the rod is pushing to the outside of the block? If so, that is excessive and should be addressed. You see that much wear sometimes in small block 400 Chevs, due to the short rods, it puts excessive side load on the piston skirts. Talk with your machinist and see what he suggests.
The wear is on the inside, or intake manifold side of the cylinder bore. Looking into the bores with a light now that the motor is out, it looks like all cylinders are the same.
tcuillier
10-31-2010, 11:13 PM
What side is all of the wear on? The outside, when the piston is going up and down in the bore the rod is pushing to the outside of the block? If so, that is excessive and should be addressed. You see that much wear sometimes in small block 400 Chevs, due to the short rods, it puts excessive side load on the piston skirts. Talk with your machinist and see what he suggests.
I was going to say the same thing, pretty severe scuffing. Usually only see that on a stroker motor.
Tom
grapejuice1998
11-01-2010, 01:02 AM
I was going to say the same thing, pretty severe scuffing. Usually only see that on a stroker motor.
Tom
Even on my 408 with over 60k miles on it, the scuffing doesn't look that severe. There is some there, but it's not that scratchy looking.
Addicted2Blue00
11-01-2010, 01:04 AM
bore and stroke it! you know you want too
bore and stroke it! you know you want too
It's already bored .030. Don't want to stroke it. It's still my daily driver(when it runs)
kota360
11-01-2010, 01:12 AM
With that scuffing being on the inside, there has to be something else happening as that is the non-load side of the piston. If that piston had come out of my 2 stroke snowmobile engine, and been on the intake side, i would say that it swallowed a ton of snow or water. Knowing that is not the case, I would say you have some type of bore issues, because that piston looks like it has been in there tight.
bfranzel
11-01-2010, 01:13 AM
well shit dude. duner and i both know the feeling of roaching pistons recently:rtfm:
With that scuffing being on the inside, there has to be something else happening as that is the non-load side of the piston. If that piston had come out of my 2 stroke snowmobile engine, and been on the intake side, i would say that it swallowed a ton of snow or water. Knowing that is not the case, I would say you have some type of bore issues, because that piston looks like it has been in there tight.
Really don't know. The machine shop had the pistons when they bored the block. I didn't assemble it, so don't know what all went on with that, the rod bearing looked fine, maybe a little extra wear on the rod side bearing compared to the cap side, but nothing that would alarm me. Still not sure why the piston broke like it did, unless the ring gap was too tight. I pulled off the top ring and slipped it into the board. Don't have a proper feeler gauge to check the ring gap though.
White Turbo
11-01-2010, 02:28 AM
What brand/type of piston are those Brian?
Do you happen to know what your PTW clearance is?
JE SRP pistons, I have no clue what the PTW clearance is. I paid "Sams guy" in San Diego to get all the machine work done and assemble the short block for me. The machine shop had possession of thee piston whn they bored the block.
kota360
11-01-2010, 05:27 PM
All you need to check ring gap is any type feeler gauge(preferably straight). Set the ring in the bore and square it with the piston and check the gap. The piece that broke out of the piston could have happened from detonation, as too tight a ring gap shouldn't make that happen on a forged piston.
Well,it could be detonation. Come to find out I'm probably running about 11:1 to 11.5:1 compression and had filled up with 89. A/F readings were always good on my wideband so never really worried about it.
kota360
11-01-2010, 10:17 PM
Damage like that you might not even hear. With that much compression and running 87 octane, even though your air fuel was reading good, detonation now would seem to be the likely suspect. Also looking at the piston in the picture, the outer edge seems to be rough with little pock-marks, and that would be detonation showing on the piston.
Duner
11-01-2010, 10:27 PM
Damage like that you might not even hear. With that much compression and running 87 octane, even though your air fuel was reading good, detonation now would seem to be the likely suspect. Also looking at the piston in the picture, the outer edge seems to be rough with little pock-marks, and that would be detonation showing on the piston.
That missing piece of the piston will make some marks too before randomly ricochets around in there long enough to make it past the exhaust valve. Getting trapped in the intake valve or exhaust valve will let the piston smack it enough to start making smaller chunks to get past the valve if it's too big to begin with. You usually get some really nice marks before it leaves.
With all that being said - it could have certainly been detonating as well.
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