Ok I know my ignition was running really advanced like past 30 deg under 22 psi when this happened so I am ruling that as the best possibility as to why this happened (plenty of oil and pressure). But I just want to check with some of you on here to see. My machinist says that it is scuffing but not from heat or detonation.
anyone have any input as to what this looks like to you or to what may have caused this.

http://portfolio.iu.edu/ekernel/P1010014.JPG [IMG][/IMG]

 

?

 

its that a je piston?mine got damaged the same way,f**ck je,now i use cp

 

I am 100% sure that is detonation. 30 degrees is way too much, no more than 20 on pump gas and thats at lower boost levels, no more that 26 at any boost level on any octane gas on a B series engine.

 

I would say that looks more like you had pistons that were the wrong size for your bore, or somthing along those lines. What prevents pistons with scratches on the sides from being re-used?

It really seems like you got your motor overbored and they gave you stock sized pistons

 

pump gas?

 

Well these are wiseco pistons never had a problem w them.

I was running c-16 fuel

YES these were right for the bore trust me I checked and double checked the pistons and bore with a mic and teloscopic bore gauge before I installed them perfect .004 clearance.

detonation would be what I thought but on the tops of the piston there is no sign of any det.

Heres what I think... The timing was way way off like way more than 30 deg advanced and that when the mixture would fire the piston still had about 1/4 of its stroke left and the fuel igniting would burn the oil off the walls and then at 6500rpm it was enough to create enough friction to scuff the piston..

Anyone think this sounds feasable

 

detonation and excessive combustion temps go after the weakest parts of the piston first(ring lands and rings)

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 30psi Teg &raquo;</TD></TR><TR><TD CLASS="quote">YES these were right for the bore trust me I checked and double checked the pistons and bore with a mic and teloscopic bore gauge before I installed them perfect .004 clearance.
</TD></TR></TABLE>

What portion of the piston were you measuring?

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 30psi Teg &raquo;</TD></TR><TR><TD CLASS="quote">Heres what I think... The timing was way way off like way more than 30 deg advanced and that when the mixture would fire the piston still had about 1/4 of its stroke left and the fuel igniting would burn the oil off the walls and then at 6500rpm it was enough to create enough friction to scuff the piston..

Anyone think this sounds feasable</TD></TR></TABLE>

Even with an abundance of lubrication the piston skirts shouldn't be making contact with the cylinder walls.

Just for a comparision... This is a picture of a piston that came out of my motor that had been built with incorrect cylinder wall to piston clearances.

 

Ran the motor lean and got it hot....

 

Are those pistons useable at all?

 

regardless of what happened that piston does not look re-usable... But it really doesen't look detonation induced, it looks almost like incorrect piston to wall clearances, or perhaps low or no oil getting to the piston.

Brad

 

This is what happened. The excess ignition timing caused the cylinder temperature to become too high. The first thing that happens is the rings expand to the point that the gap goes to zero and they butt together. This causes all the oil to be scraped from the cylinder walls and galls the side of the piston.
If the piston to wall clearance was wrong, the scraping would start at the BOTTOM of the piston skirt and work it's way up. In your case it starts at the ring lands and works it's way down. This is classic overheating of the piston. It happens so fast, there is no way your cooling system can begin to remove the heat.
Too much timing or too little fuel will give you the same results.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by earl &raquo;</TD></TR><TR><TD CLASS="quote">This is what happened. The excess ignition timing caused the cylinder temperature to become too high. The first thing that happens is the rings expand to the point that the gap goes to zero and they butt together. This causes all the oil to be scraped from the cylinder walls and galls the side of the piston.
If the piston to wall clearance was wrong, the scraping would start at the BOTTOM of the piston skirt and work it's way up. In your case it starts at the ring lands and works it's way down. This is classic overheating of the piston. It happens so fast, there is no way your cooling system can begin to remove the heat.
Too much timing or too little fuel will give you the same results.</TD></TR></TABLE>

I am going to say that you are right. I know the piston to wall clearance was right measured 1in up from botm of skirt and got .004 clearance. I think that the overheated piston theory is right.

Thanks For all the input, helps alot.

 

good info on this page