engine questions

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Tedwong
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engine questions

Post by Tedwong »

Hi all you engine experts there, asking on behalf of my friend about his 998 engine.
The engine recently suffered from knocking, then a bit high temp. and finally blown the gasket between 2-3 cylinders.
When opened, he found some metal residual stick/weld on the cylinder top. All four cylinders.
Just want to know what are these? Piston looks fine, no damage.
Thanks!
Ted

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LDR209H
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Re: engine questions

Post by LDR209H »

Any valve damage ?
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Tedwong
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Re: engine questions

Post by Tedwong »

No, valves all good.
36inter
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Re: engine questions

Post by 36inter »

That looks like detonation debris to me from the piston, looks like aluminium. My best guess.

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Re: engine questions

Post by mk1 »

That's what I thought Pete, But Ted says that the piston looks perfectly normal?????
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Vegard
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Re: engine questions

Post by Vegard »

Have the pistons been removed from the block? A lot can happen below the crown which isn't visible from the top.
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Re: engine questions

Post by guru_1071 »

Vegard wrote:Have the pistons been removed from the block? A lot can happen below the crown which isn't visible from the top.


thats my thought exactly
please note, these are my own, individual sales, nothing whatsoever to do with my employer, minispares
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Frogeye61
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Re: engine questions

Post by Frogeye61 »

The aluminium (piston) between the ring lands has melted a bit, or maybe even the rings have disintegrated.
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Re: engine questions

Post by 2ramp3 »

Two things there appears to be vertical scratching on the bores inline with splatter which would suggest piston or piston ring . Piston being alloy should,nt be difficult to remove from the bore metal from the rings not so.My monies on the rings .
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Tedwong
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Re: engine questions

Post by Tedwong »

Dear all, thanks for the answers. He has not removed pistons as he changed gasket in situ. But now seems he has to remove the engine to find out what's happening. Will keep you inform about the results.

Ted
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Re: engine questions

Post by 970s »

:o
Ted,
I posted the same issue just now, seems detonation is hte answer, cause timing is way out for quite a period, with knocking on engine!
Same problem with high CR motors with wrong timing set! The whole piston crown melt!
Hope nto to remove pistons! :(

Al
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Tedwong
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Re: engine questions

Post by Tedwong »

Engine now pulled apart, so here is the answer. As suggested by all of you, metal debris from the unseen area of pistons crown:

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Re: engine questions

Post by mk1 »

Ouch!
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Re: engine questions

Post by 36inter »

It might be worth checking the con rods just to be sure they are not bent or twisted, as it is apart it would be silly not to do this. Also check there is no side thrust on the pistons when assembled.

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Tedwong
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Re: engine questions

Post by Tedwong »

36inter wrote:It might be worth checking the con rods just to be sure they are not bent or twisted, as it is apart it would be silly not to do this. Also check there is no side thrust on the pistons when assembled.

Pete

Thanks Pete, will do!
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