2005 EJ25 Block w/Phase 1 EJ25D heads? Bent valve damage piston?

[wtdash]

2005 Phase 2 2.5 SOHC from an Impreza - non-turbo, 70K miles, bent valve due to idler pulley failure, which caused the T-belt to skip.

 

(According to wikipedia this is an EJ253...which was also used in the '99 Forester/Impreza??)

 

Can I install my Phase 1 EJ25 DOHC heads (edit: from a '98 Forester Phase 1 EJ25D block) on it and go?

 

I've read the '99 Legacy series used the EJ25D heads and Phase 2 block, but 2005 is new enough to make me wonder.

 

(I know I'll only use 1/2 the mounting bolts to connect to my transmission.)

 

Would/could the valve damage the piston/block in any way?

 

Thanks,

Td

Edited December 9, 2010 by wtdash
added SOHC clarification

[idosubaru]

you won't have the bellhousing bolt difference in a 99 and 2005.

 

shouldn't be piston damage as there's no valve to piston interference.

[wtdash]

shouldn't be piston damage as there's no valve to piston interference.

 

So, the valves hit each other, not the pistons, correct?

 

Thanks!

[svxpert]

the 2005 engine is most likely SOHC unless it a turbo (STi)

if it is a SOHC engine you would be putting DOHC heads on it. you would at the very least need the intake manifold and exhaust from the DOHC engine, plus other parts.

[idosubaru]

So, the valves hit each other, not the pistons, correct?

 

Thanks!

correct. only valves collide in EJ25's. now...could a valve collide, break, and the scar the piston and cylinder walls - i don't know. i haven't seen it or heard of it happening before.

[wtdash]

the 2005 engine is most likely SOHC unless it a turbo (STi)

if it is a SOHC engine you would be putting DOHC heads on it. you would at the very least need the intake manifold and exhaust from the DOHC engine, plus other parts.

 

Yep...been there/done that, but thanks for clarifying for others. (updated OP to show it's a SOHC.)

 

Td

Edited December 9, 2010 by wtdash

[wtdash]

correct. only valves collide in EJ25's. now...could a valve collide, break, and the scar the piston and cylinder walls - i don't know. i haven't seen it or heard of it happening before.

 

Gary, I read on another Subaru forum that on the SOHC (which this is from - a non-turbo EJ25 on a 2005 Impreza), that since there's only one camshaft per head the valves wouldn't/couldn't collide, so it probably did hit the piston to bend....

 

Can you verify this?

 

Thanks for your help!

[idosubaru]

Hmm, good question - experience suggests I wouldn't expect to see any piston damage......but I'm not sure why and could be wrong.

 

SOHC is confusing because earlier SOHC EJ22's are not inteference engines (1990-1996). But later SOHC EJ25's are interference, so I think that acronym confuses people since SOHC doesn't refer to one engine but sometimes it seems like it does.

 

What you're really asking is about Phase II EJ25 interference - I thought technically speaking they are valve to valve and valve to piston interference but usually only sustain valve damage when the belts break - I've never seen or heard of piston damage.....

[Qman]

SOHC interference motor... valve damage resulting from breaking/slipping belt. Valve timing is now off. Valve contact with piston. Valve to valve contact can only occur after the piston hits and bends the valve. You will see some form of scarring on the piston. How severe varies from how far out the timing was when contact occured.

 

Now to the question of head swapping. It can be done. However, you have wiring issues. You have part compatablity issues. You basically need the entire engine to have all the parts you will need. Inspect your current heads for damage. I can sell you used valves if you need them to keep costs down. Then you just need a tensioner, belt and gaskets plus a valve job. Wiki is not a good source of information for Subaru. There is far better information on USMB, RS25 and Nasioc for this type of problem.

 

Again, when giving advice, know your topic. DO NOT GUESS!

Edited December 9, 2010 by Qman

[Fairtax4me]

Piston damage from a valve crash is minimal. Plenty of people have rebuilt the heads, put it back together, and have 0 problems from the small nicks that the top of the pistons get from the valves.

 

Rebuild the heads and put it back together. Too much work to make dohc heads fit.

If you have a whole DOHC engine you might be able to drop that in with some changes. But I'm not familiar with the differences between those engines other than the heads, so I have no idea what would need to be done.