Page 1 of 1
engine questions
Posted: Fri Jul 13, 2012 8:13 am
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
Re: engine questions
Posted: Fri Jul 13, 2012 8:36 am
by LDR209H
Any valve damage ?
Re: engine questions
Posted: Fri Jul 13, 2012 8:51 am
by Tedwong
No, valves all good.
Re: engine questions
Posted: Fri Jul 13, 2012 9:46 am
by 36inter
That looks like detonation debris to me from the piston, looks like aluminium. My best guess.
Pete
Re: engine questions
Posted: Fri Jul 13, 2012 9:52 am
by mk1
That's what I thought Pete, But Ted says that the piston looks perfectly normal?????
Re: engine questions
Posted: Fri Jul 13, 2012 11:47 am
by Vegard
Have the pistons been removed from the block? A lot can happen below the crown which isn't visible from the top.
Re: engine questions
Posted: Fri Jul 13, 2012 12:21 pm
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
Re: engine questions
Posted: Fri Jul 13, 2012 8:36 pm
by Frogeye61
The aluminium (piston) between the ring lands has melted a bit, or maybe even the rings have disintegrated.
Re: engine questions
Posted: Sat Jul 14, 2012 12:18 am
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 .
Re: engine questions
Posted: Sat Jul 14, 2012 3:05 am
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
Re: engine questions
Posted: Mon Jul 16, 2012 5:57 am
by 970s
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
Re: engine questions
Posted: Thu Jan 31, 2013 8:24 am
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:
Re: engine questions
Posted: Thu Jan 31, 2013 8:32 am
by mk1
Ouch!
Re: engine questions
Posted: Thu Jan 31, 2013 12:01 pm
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.
Pete
Re: engine questions
Posted: Fri Feb 01, 2013 9:18 am
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!