Harper1

hoping to get some advice from you guys that know your Subaru engines,

I have a 96 WRX STi. Was out for a run on Friday night when i lost quite alot of power, and what i thought was the spark in a cylinder. I stopped and let it idle and it sounded like it was misfiring on a cylinder. As i wasn't far from home, i crawled back to seek some advice on Saturday. A local garage who have had experience in Subarus informed me that it was a big end bearing or possibly a hole in a piston. So up bright and early yesterday and whipped out the engine in about 5 hours. What did scare me tho, was when i took the plugs out (which i should have done first!!!), i found the tip was broken off completely on the 2 back plugs. Strange i thought, so decided to investigate a bit further. Checked the timing.....everything seems ok. Took the starboard side cylinder head off, aha! A hole in a valve! No damage to cylinder bore, but a slight ding on the piston.

How could this have occured? Is it possible that the spark plug broke up first, then punctured the valve? i think the big ends are ok, there seems to be no play in the crank at all.

Any help is much appreciated.

Cheers,

Kyle

GariYaRally

Have seen a number of engines with damaged valves from valve-valve damage. Usually occurs when cowboys fit timming belt in correctly. If the cam shafts are rotated in the opposite direction, the inlet/exhaust valves come in contact.
It could be this, I could be wrong though.

p1mark

How do you mean a hole in the valve? do you mean the outer diameter is breaking away? is it an inlet or exhaust valve?

Harper1

heres a pic, can't be valve to valve because there's a mark on the piston where it has hit the valve

cheers.