2005 Impreza EJ25 SOHC, 70K (i was told) - pulley seized, broke the T-belt and bent a valve. I bought it to take a chance on the piston being undamaged...well...

 

So THAT'S what happens when a valve hits the piston :

 

edit: Here's head:

Can I just replace the piston? I've got another set of heads that I was going to use on this.

Thanks,

Td

Edited January 24, 201115 yr by wtdash

...Can I just replace the piston? ...

 

I Believe that will Depend on How the Cylinder Wall is... Have you Checked if the Pushed Piston did damage it? ...

By Seeing the Photo I Don't Believe it could get Damaged, but it Worth to Check that, to Avoid future Problems.

Kind Regards.

I agree that it's worth taking a bit of time to see if the valves did any gouging to the cylinder wall before they stopped moving. If they did, you'll need to smooth and polish the cylinder wall before you reassemble the heads. As to the piston, from the picture, it almost looks like the damage is superficial and the top of the piston head could be polished out. Cannot say for sure with pictures being 2D, but it appears to be a possibility. If you have another piston head available, it would be possibly less work to swap them, but that's up to you.

If the cylinder wall is undamaged, I would consider not replacing the piston. Like earlier said, it looks like cosmetic damage to the piston. Clean the top of the piston, and then judge what damage is really there. I have read repeatedly here on this forum, that a broken timing belt does not damage the piston top.

^Even though the piston is cracked down the middle? (That's not sarcasm - as I don't know whether the crack is bad or not.)

 

I just looked @ the cylinder wall and there are 2 marks @ the top of the cylinder wall:

 

 

 

That's the only damage....but Should the piston be perfectly flush w/the top of the cylinder when @ the top? One side is slightly lower than the other. Due pistons have a bit of 'wobble'?

 

Thanks

Edited January 19, 201115 yr by wtdash

No, you can't use a cracked piston. Crack = bad.

 

Those scars at the top of the cylinder aren't good news either. The piston comes right up to that point, and if the rings go past those marks they will leak compression and probably end up burning out.

Generally that type of mark is too deep for machining.

With that type of top end damage, the rod is probably bent as well.

 

Talk to whoever you bought it from, and tell them the engine is damaged beyond repair, and you need your money back.

Wash your hands of it, and go to car-part.com and find another engine.

Take a small whet-stone to those couple little marks, have the cylinders power-honed and it will likely be fine. The rings don't come up as far as those marks on the chamfer of the liner.

 

And no - dont use a cracked piston like that. That thing is scrap metal.

 

GD

Thanks for the replies......I added another view of the piston damage above. It's a little clearer, and the piston damage more obvious.

here goes the thread for those of you saying interference will not harm the pistons, or the block. This thread shows what can happen, darn it Subaru, why not stay with non-interference this would never of happened in any ej22 of pre95

 

So all those posts, saying the block is fine when a t belt snaps, well, here is the pudding of the proof.

251/253 blocks will take damage - but from what I understand the "interfereance" on the 25D is valve/valve due to the DOHC system. In other words the pistons still don't reach high enough to tap a valve.....

 

GD

does anyone know if the FB25(new block subaru is introducing in the 2011 Forester) is a interference design?

Edited January 19, 201115 yr by bheinen74

does anyone know if the FB25(new block subaru is introducing in the 2011 Forester) is a interference design?

 

there is no reason to think that it would be NON-interference. given the need for power and emissions demands i would think that they would squeeze everything possible out of an engine design.

 

i really don't know how far valves extend out of the block or what it would do the power production of the engine to shorten the stroke enough to avoid the engine. but i assume that there is horsepower in that last little bit.

 

but again, i don't really know.