Damaged Wiseco Pistons (Not Pretty)

[VTEC_THIS]

The outcome of this thread can be seen here:
http://www.dsmtuners.com/forums/cyl...iseco-pistons-not-pretty-4.html#post152902133
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About a week ago we took the car out for a cruise and heard a light tapping that very shortly later turned to a much louder tapping/rattling noise. We had our laptop with us so we started logging through ECMLink and saw that knock was being picked up continously so we headed straight home and shut the engine off immediately.

This has happened to us once before (on a previous DSM) so we were pretty certain we spun a rod bearing. We pulled the engine yesterday and dissasembled the shortblock last night. Well, the rod and main bearings were fine... apparently the pistons weren't though :

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[Bud92gsx]

I'm pretty sure that is not supposed to happen

That's some nice carnage their tho.

 

[Talon64]

That hurts just looking at that. Do you have any clue why it did that?

 

[VTEC_THIS]

Upon further inspection, I found stress cracks in all of the pistons.

I'm going to contact Wiseco tomorrow morning but is this something that they should cover?

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[VTEC_THIS]

That hurts just looking at that. Do you have any clue why it did that?

I honestly don't know, I would love to know myself. The engine had exactly 13,500 miles on it when it happened.

This isn't the first time this has happened either:
http://www.dsmtuners.com/forums/bolt-tech/140790-cracked-wiseco-piston-skirts.html

 

[donniekak]

Standard wisecos always crack there. Running improper ptw clearance, or hard driving before the engine is fully warmed up can increase the damage.

 

[BoostedBeaver]

Were these the standard Wiseco's??? Just wondering and interested in what Wiseco has to say.

Robert

 

[eclipsegsx1736]

Was this a 2.3 stroker? My first 2.3 engine had std Wisecos and went for almost 65,000 miles before the above happened to me as well, although only on a single piston. Same noise and logged knock. Although, I knew the engine was done and I already had a spare on the way, so I cranked up the boost and did a pull to ~ 8k RPM with it like that, only to crack the cylinder wall..

Apparently many people have seen these cracks develop, but as far as I know it's significantly more rare for there to be a failure like this.

 

[ed1380]

What is considered recommended ptw for the strokers? I don't want that happening

 

[blackrosenova40]

I had them stress cracks on all four of my wiseco's and I had a wrist pin snap in half on one of them.

 

[VTEC_THIS]

These were the Wiseco standard forged pistons for a 2.0L (6 bolt, .020 over, 9.0:1 CR), not the stroker pistons.

Whether they're standard or heavy-duty forged I don't think that should be an excuse for this happening. They're forged, made by a reputable company and relatively expensive.

If you look closely at the pictures, all of the cracks happened in the exact same spots on the pistons. I don't know if this is a weak spot on the pistons or a manufacturing defect/flaw but I don't think this should be "the norm" or expected to happen on standard forged pistons.

 

[danl]

Did it hurt the block? How high did you rev it to?

 

[VTEC_THIS]

Surprisingly it didn't damage the block. The cylinder walls are relatively intact, some scuff marks but nothing out of the ordinary for a used shortblock. The main and rod bearings as well as the connecting rods and crankshaft were also (surprisingly) in great shape considering what happened to the pistons!

I never went past 7,500RPMs.

 

[1983gsp]

Incorrect ptw clearance is my vote. Hope its a manufacturer defect so you can recoup something for your loss. Good luck.

 

[kidtsi]

What were your PTW clearances? My first set made it to 90k miles.

 

[ilco187]

ouch, i had a similar problem i had .20 overs and they cracked and one was bad enough it melted the wristpin and piston together. i stay away from wiseco.

 

[kidtsi]

ouch, i had a similar problem i had .20 overs and they cracked and one was bad enough it melted the wristpin and piston together. i stay away from wiseco.

Melting a piston is not piston failure, you have to reach a certain temperature before that happen. Tune was your failure.

 

[JacksonAuto]

I see a lot of black crud built up on the sides of the pistons (near where the pin is. Look at pic no. 5) and also see a lot of carbon/fuel tracking near the oil holes on the underside of the piston. There is also a fair amount of caking on the undersides. This is caused be high oil temperatures. There is also an abnormal amount of scuffing on the skirts.

So, there is evidence that the pistons were run with insufficient wall clearance. The question is why. Scenario "A" is the PTW clearance was set too tight from the beginning and that caused the oil to build temperature and the skirts scuffed and eventually collapsed (caused the cracks) and then the one just let go.

The other scenario is that you've got an oiling problem which caused it to heat up or you washed the rings out with too much fuel. This created more friction (and heat) which caused the pistons to expand too much, wear prematurely and fail. The tracking near the oil holes makes me believe this is the more likely scenario.

So what came first, the chicken or the egg?

 

[kidtsi]

I see a lot of black crud built up on the sides of the pistons (near where the pin is. Look at pic no. 5) and also see a lot of carbon/fuel tracking near the oil holes on the underside of the piston. There is also a fair amount of caking on the undersides. This is caused be high oil temperatures. There is also an abnormal amount of scuffing on the skirts.

So, there is evidence that the pistons were run with insufficient wall clearance. The question is why. Scenario "A" is the PTW clearance was set too tight from the beginning and that caused the oil to build temperature and the skirts scuffed and eventually collapsed (caused the cracks) and then the one just let go.

The other scenario is that you've got an oiling problem which caused it to heat up or you washed the rings out with too much fuel. This created more friction (and heat) which caused the pistons to expand too much, wear prematurely and fail. The tracking near the oil holes makes me believe this is the more likely scenario.

So what came first, the chicken or the egg?

Cant say it more clearly, awesome post.

 

[VTEC_THIS]

I see a lot of black crud built up on the sides of the pistons (near where the pin is. Look at pic no. 5) and also see a lot of carbon/fuel tracking near the oil holes on the underside of the piston. There is also a fair amount of caking on the undersides. This is caused be high oil temperatures. There is also an abnormal amount of scuffing on the skirts.

So, there is evidence that the pistons were run with insufficient wall clearance. The question is why. Scenario "A" is the PTW clearance was set too tight from the beginning and that caused the oil to build temperature and the skirts scuffed and eventually collapsed (caused the cracks) and then the one just let go.

The other scenario is that you've got an oiling problem which caused it to heat up or you washed the rings out with too much fuel. This created more friction (and heat) which caused the pistons to expand too much, wear prematurely and fail. The tracking near the oil holes makes me believe this is the more likely scenario.

So what came first, the chicken or the egg?

Thanks for the response.

Would washing the rings out with too much fuel cause low compression? The reason I ask is because before we pulled the engine we did a compresion test and it was almost consistently 190 across the board.

Just to clarify, is this the picture you were referring to with the black crud? It might be hard to tell from the picture but I believe what you're seeing is what's left of the piston coating:

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Also, the only piston I've found with abnormal scuffing is the one that was completely destroyed:

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[JacksonAuto]

Washed out rings wont necessarily cause low compression test results. The pressure in the cylinder without combustion taking place is simply too low to reveal the poor ring seal. A leakdown test would have revealed a problem, though.

The Wiseco pistons have coated skirts. The whole piston is not coated. The black crud that I'm referring to is adjacent to the pin bore. Well away from where Wiseco applies the coating.

On the rest of the pistons, the skirt coating is gone. This is abnormal scuffing/wear.

 

[JacksonAuto]

When the engine was assembled, what were the pin bore clearances? If too tight, the pins can seize in the bores and also cause this type of damage. This is a very common problem with DIY'ers because they don't know to check. Out of the box, parts are not ready to assemble. Every set of pistons I've ever installed had to be pin-fit because the clearance from the factory was too tight. Same with the rods.

 

[VTEC_THIS]

Thank you for clarifying that. I didn't assemble this engine myself, it came with a DSM I purchased over the summer.

When the engine was assembled, what were the pin bore clearances? If too tight, the pins can seize in the bores and also cause this type of damage. This is a very common problem with DIY'ers because they don't know to check. Out of the box, parts are not ready to assemble. Every set of pistons I've ever installed had to be pin-fit because the clearance from the factory was too tight. Same with the rods.

What were your PTW clearances? My first set made it to 90k miles.

I'm not sure what the pin bore clearances were when the shortblock was assembled but I'll try to get the PTW clearance numbers tomorrow from my machinist when I bring the block to him. Unfortunately I don't have anything to measure the PTW clearance myself.

 

[white92talontsi]

I agree with what JAM has said.

Too tight PTW will cause that and also too tight on the wristpin can cause the piston to walk in the bore pretty badly.

 

[bastarddsm]

There is also an abnormal amount of scuffing on the skirts.

So, there is evidence that the pistons were run with insufficient wall clearance. The question is why. Scenario "A" is the PTW clearance was set too tight from the beginning and that caused the oil to build temperature and the skirts scuffed and eventually collapsed (caused the cracks) and then the one just let go.

What is your recommended ptw clearance for a hot street motor? How about rod to pin, and piston to pin?


I've got around a little 10k on my shortblock so far, and just had the pan off not that long ago. My pistons looked good inside, but I didn't look that closely. Now I'm paranoid and feel like I should take it apart and check it over good.