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Old 11-23-2012, 02:48 PM   #1
ripman
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Default Hairline cracks between spark plug and valve seats?

I'm having trouble trying to find a decent set of '99 wrx heads for my build. They seem OK until I have them chemically cleaned, then there are hairline cracks exposed between the spark plug entry and the valve seats.

I had a set pressure tested and the came up fine, but I noticed in a couple of threads here that more experienced engine builders are not prepared to use these heads.

I spoke to the machine shop about it. They said they could last forever/or they could be fixed but we looked at the process together and it was time consuming.

My question is what issues have people found and at what sort of boost and hp levels?
Have people used heads like this on high hp builds without any issues?
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Old 11-23-2012, 03:19 PM   #2
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You like that! and I still run it
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Old 11-23-2012, 03:43 PM   #3
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I'm not seeing anything that bad Fuji. Are you saying it has not been a problem for you?
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Old 11-23-2012, 05:21 PM   #4
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My machine shop would NOT service any heads with these cracks. It took us quite a long time to find a set of EJ205 heads without these cracks. It is very common. However, once we finally found a set, they reinforced the areas where it's prone to crack so they would not crack in the future.

After that, they went ahead and opened up my chambers and did a full valve job. You can't really blame them for not wanting to put work into heads with these cracks.
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Old 11-23-2012, 06:08 PM   #5
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There are other manufacturers of engines with heads that develops the same cracks and will drop a valve seat. Any machine shop would not let this pass. They don't want to be held liable.

For Subaru, i haven't heard of anything happening yet since these engines die in some way or form before the cracks become an issue. If anyone who has experienced more issues as a result from these cracks, i would like them to share their experience.

I actually would like to buy some "cracked heads" to do long term tests.
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Old 11-23-2012, 06:29 PM   #6
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Fuji, I've never seen any cracks on the phase1 engines I've had over the years.

I wonder if this is unique to the phase two heads.
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Old 11-23-2012, 06:52 PM   #7
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For some reason I can not post attachements so unfortunately can't show picture of cracks. They can only be seen from up very close with the naked eye, so will be interested to hear views on running them.
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Old 11-23-2012, 07:00 PM   #8
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anyone know the cause? i wonder if it has to do with the hardened valve seat that is pressed in?
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Old 11-23-2012, 07:12 PM   #9
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pretty common, I've heard of issues with random misfires but if they were fine before you removed them they're probably still fine.
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Old 11-23-2012, 09:12 PM   #10
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it caused us to drop out of one lap. More coming when I'm not on a phone.
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Old 11-23-2012, 09:29 PM   #11
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As Fuji said. It is a common issue for many engines. Some it causes the seat to drop others(like Subaru) it doesn't seem to cause much of an issue too often, not that it doesn't cause any...

It is actually common in many air cooled motorcycle engines. Many shops don't even have an issue working on these, they will do a valve job , note it and give them back if you wish.

It is entirely possible to remove the seats, repair the crack, chase the plug hole and remill the pocket for the valve seat. IME they will crack again in time.

In Harley's case on the Evolution many shops will also weld in the 14mm plug hole while repairing the crack and drill and tap it for the later Twin Cam 12mm plug giving more meat between the seat and hole, which seems to be the long term cure.
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Old 11-23-2012, 09:40 PM   #12
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If the cracks get too huge, I'd look for another head.

Makes me wonder if I ran a brand new head with a 1 step colder plug, would it prevent this?
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Old 11-24-2012, 03:48 AM   #13
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eg33 - I have seen a few ej25d phase 1 heads with the same cracks when I was at the Subaru dealer. Definately a known problem in all the twin cam heads. However, most of the time you wouldn't notice a problem until you're replacing the shortblock for bearing or ringland failure.
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Old 11-24-2012, 04:03 AM   #14
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Quote:
Originally Posted by FuJi K View Post
If the cracks get too huge, I'd look for another head.

Makes me wonder if I ran a brand new head with a 1 step colder plug, would it prevent this?
Cracks even bigger than what they are now??? Those are the biggest cracks I've seen in Subaru heads... (and I've seen quite a few) I think you are pushing as there is a risk that a valve seat will drop at some moment. But if you are comfortable with that, it's no problem of course.

1 step colder plug won't help. I've seen heads with big cracks and those engines had colder plugs in from new.

I have no 100% proof, but I expect the cracks to form when running too much power before the engine is up to it's "normal" coolant temperature.
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Old 11-24-2012, 09:25 AM   #15
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In Aircraft Engines cracking between plug hole and Exhaust valve seat is not uncommon and it's attributed to heat Management. This is supported by improved cooling fin design in the area reducing or stopping the problem from happening and that it's often found on Engines with poor baffle seal.

Does anyone have cylinder head temp probes on an Engine where the cracking occurred? Is there a trend in what cylinder the heads are cracking on?
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Old 11-24-2012, 04:53 PM   #16
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Quote:
Originally Posted by Surb00 View Post
eg33 - I have seen a few ej25d phase 1 heads with the same cracks when I was at the Subaru dealer. Definately a known problem in all the twin cam heads. However, most of the time you wouldn't notice a problem until you're replacing the shortblock for bearing or ringland failure.
So what did the Subaru dealership do with them? Re-use due to it not having caused a problem, or reccomended to customer to replace them?

The cracks I'm seeing are more the same as in Flat 4's photo and came off a good running motor.
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Old 11-25-2012, 02:55 PM   #17
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I've never seen a set pulled off a car that DIDN'T have the cracks. Sometimes you can't see them until the heads are cleaned up.
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Old 11-25-2012, 09:57 PM   #18
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I have built three 02 rex's lately and I couldn't find any cracks. I have seen these cracks on past engines and have used the heads with no problems. Not as bad as fuji's though.
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Old 11-27-2012, 12:13 AM   #19
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ripman - We'd document the cracks and send it down the road! Usually it is no problem. It's 3 different materials with different rates of thermal expansion in an extremely high temp environment somethings going to give.
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Old 11-27-2012, 04:25 AM   #20
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Quote:
Originally Posted by Surb00 View Post
ripman - We'd document the cracks and send it down the road! Usually it is no problem. It's 3 different materials with different rates of thermal expansion in an extremely high temp environment somethings going to give.
Thanks Surb. Good to know. Most of the comments have me reasonably comfortable to run these heads.
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Old 11-27-2012, 03:40 PM   #21
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Quote:
Originally Posted by FuJi K View Post
There are other manufacturers of engines with heads that develops the same cracks and will drop a valve seat. Any machine shop would not let this pass. They don't want to be held liable.

For Subaru, i haven't heard of anything happening yet since these engines die in some way or form before the cracks become an issue. If anyone who has experienced more issues as a result from these cracks, i would like them to share their experience.

I actually would like to buy some "cracked heads" to do long term tests.
you would like to buy some crack?????
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Old 11-29-2012, 09:58 PM   #22
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Curious if anyone knows if this occurs across the board on heads from 1990 up to current?
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Old 11-30-2012, 01:59 PM   #23
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Just found that my 2003 WRX heads have the infamous cracks. Was planning to use these in a hybrid build, but now I'm just going to get new castings to go along with the new EJ257.



How can I prevent this with a new engine? I'm going to have the new heads chamber matched and ported.
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Old 11-30-2012, 03:13 PM   #24
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I believe most causes of the cracks are from people over TQin the plugs

if you getting new castings why not get ones for a ej257 so you dont have to pay for the chamber matching..
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Old 11-30-2012, 03:24 PM   #25
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Quote:
Originally Posted by Paul View Post
I believe most causes of the cracks are from people over TQin the plugs

if you getting new castings why not get ones for a ej257 so you dont have to pay for the chamber matching..
I think there are far too many instances of spider cracks for it to be everyone over-torquing the plugs.

Wouldn't I then have to run AVCS? If so, wouldn't that mean drastic ECU changes? Also, I already 2.0L cams, bucks, springs and valves.
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