help piston damage (pics)


D

dave benson

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Jul 24, 2008
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hi, well after only 200 miles, 30 of which were on a stage rally this is the state of my new engine, it was bored 0.5 oversize and had new je racing forged pistons, was run in on a rolling road and then mapped(running itb's and toda vtec killers)

when i picked it up from the rolling road, he said it had been mint and was ready to go, so did two rally's but retired with water in electrics and gbox trouble. only took the engine apart as it started to smoke on idle, but when we went onto the next stage it was fine under load, no smoke, so thought it was valve stem seals

it has never been hot or overheated, runs half size alloy rad and an oil cooler

what do you guys think has happened ?

cheers
 

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Looks like something got ingested into the engine. How is your filter looking?
 
piston clearance too tight or that cylinder was running very hot
 
tama666 said:
Looks like something got ingested into the engine. How is your filter looking?
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Its too low down to have been that imho

Were the bores checked for ovality?

May be something in the picture but it looks like there is something embedded in the oil control ring
 
What was the piston to wall clearence ? What compession ratio ? What's the fueling like AFR wise ?
 
100% run lean and started to det. Were you listining for det when tuning? This is why cars should always have the final map done on the road. The top of the skirt under the ring lands is always the first part of the piston to touch the wall because its the part of the piston that expands quickest, above this point is cut smaller so rarely touches. Speak to the person who mapped it
 
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Can you post more pictures up of the top of the pistons ? Like rs250nut said, it should of been finished off on the road at least. Ideally been a rally car, the track what you was on would of been best to fine tune the fueling. You needed more piston to wall clearence/richer mixture anyway by the look of those skirts.
 
Darragh_K said:
piston clearance too tight or that cylinder was running very hot
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Both good points in my opinion!:nice:

windymiller said:
Were the bores checked for ovality?
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It defiantly looks like a issue with ovalness of the bores:nerv:

With the block being bored 0.5 oversize that should rule out ovality really, but I have seen perfectly good & true boring bars bore oval bores due the the bearings in the head of the machine being f**ked.

Were did you have the machining & engine built?????

Was the honing of the bores done correctly?
 
Measure it, I would bet my house on it being round. Got any pics of the gasket, piston tops ? Did you check the plugs after?
 
the reason it was bored originally was because the bores were slightly oval, pressume that the clearances were correct but only took it apart this evening.

i was thinking they look too tight, but need to get them measured tomorrow.

all 4 bores, front and back + pistons are the same

no damage to piston crowns so cant be debris
 
No, its a too tight piston to wall clearence if your fueling was fine/rich. Post up your piston to wall clearence along with JE's recommended clearance range. What Alloy are they ? 2618
 
dave benson said:
would running very rich cause this because of washed bores ?
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I very much doubt it, if it were running rich the plugs would have been fouled. You only need a split second to do this sort of damage.
 
will find the spec sheet tomorrow and get the bores measured and post the findings

gutted that my new engine is scrap !

do you think it was not run in enough ?
 
dave benson said:
will find the spec sheet tomorrow and get the bores measured and post the findings

gutted that my new engine is scrap !

do you think it was not run in enough ?
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If built to spec it should only need the rings seating.
 
i know the rings gaps were fine as i did them myself !

the guy that bored and decked the block is very experienced has run his own machine shop for 30 years so i will be suprised if it was too tight
 
rs250nut said:
100% run lean and started to det. Were you listining for det when tuning? This is why cars should always have the final map done on the road. The top of the skirt under the ring lands is always the first part of the piston to touch the wall because its the part of the piston that expands quickest, above this point is cut smaller so rarely touches. Speak to the person who mapped it
Click to expand...


I cant see it being caused by det, i keep looking at it and it just looks like the bores arent machined right. We'll see but im intrigued:nerv:
 
How were the plugs the plugs checked ? whilst the car had been idling or under light load ? Its either A. was running to lean B. Piston to wall clearence
 
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