Hello,

My EVO 9 had an engine ticking noise on idle and up to 2500 revs.
I replaced the lifters with negative result.
After some dismantling I discovered that the piston number 4 was scraping the cylinder bock.
(photos attached)
The other three pistons and block are .
Your opinions about the probable cause are highly appreciated.

Thanks.

 

Either that's bad machining or it hasn't been balanced properly. Is the rod fine? Is this the factory block or has it been reassembled?

 

The engine is stock, never opened. (It has only 75 000 Km)
Visualy the rod is fine but am going to send it to be checked by professionals.

 

And the bearings at that cylinder are fine as well?

 

Yep , all is good.
only the piston and the block.

 

Yeah then get the rod checked just for reassurance. How much hp / torque was this motor making?

 

Full bbk turbo
M2 cosworth cams
1000 CC injectors
around 350 Bhp

 

Boost 1.8 tapered to 1.6 above 7000 revs

 

Thiss sucks bro. Could it be the intake runners making #4 run lean?

 

This doesn't look like detonation. There's something wrong with his assembly at that particular cylinder.

 

Agreed. Too dirty to be detonation (sorry, just looked at your pictures on my phone)

 

One thing is for sure No one opened the engine before.
Anyway since I'm F....ed with this failure, I'm gona get forged wiseco 85.5 HD pistons .
Should I get forged rods or the stock rods will do the job for the < 400 BHP ???

Thanks

 

OEM connecting rods are for around $500 and forged rods can be found for the same price. Go with forged rods and do it right for added durability, even if the connecting rods will withstand 400 whp.

 

Maybe running low in oil, detonation &/or maybe lean?

 

His piston doesn't show signs of detonation. It actually looks pretty good except for the dirt obviously. If he's running low in oil I doubt it will affect just one cylinder.