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Compression Test and Leak Down numbers - opinions?


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120 psi, 6% LD

120psi, 6% LD

115 psi, 7% LD

100 psi, 10% LD

 

Motor was ran up to temperature, and these values recorded within 1 hour of shutting off.

All plugs pulled while checking, fuel pump fuse pulled, all cylinders tested twice with throttle to the floor. Car burns less than half a quart every 3k miles.

 

I am looking to go stage 2 and am unsure if it is worth it with these results. Vehicle doesn't miss a beat (that I can notice atleast, and i have bad OCD...) Not worth dumping 3k into rebuilding heads when I might as well just run it into the ground...

 

This is on a 2005 LGT 5EAT wagon with 122k miles. All plugs looked equally dry, worn, and partially white.

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She’s tired. 10% leak down is max value. Less than 10 psi between cylinders is spec. How’s the turbo look? If good. Pull the banjo filter, bolt on the downpipe, load up stage 2 and ride it till she pops. In the mean time. Buy up a shortblock and prepare for rebuild.
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I'm only at ~500ft above sea level.

 

By the time I adjust the valves and what not, and buy new hard parts if necessary it seems it may just be more cost effective to buy a new long block, or just buy rebuilt heads it seems.

 

Probably better to just pull the motor, rebuild the heads, slap it together and go?

 

Not sure if there is any quality rebuild kits, with oversized valves or whatever standard is? Only motors I've torn into were older ford and Chevy push rod motors.

 

Any idea on average rebuild price for both heads? The 115 and 110 where both driver side, so I assume it may just be that head necessary? My OCD will require both to be done...

 

Perhaps prices on good short/long blocks?

 

 

If I go stage 2 as is, would it be safer to run a rich tune like Cobb OTS or still attempt for a dyno tune? Not sure if tuners would want to touch it or waste their time.

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After quick run through...

 

Version 1 Ej255.

Shortblock = AB440, same as 04-06 STi Ej257

Cylinder head = AB650..... B25 Heads

 

However, see link below, post 1... Unclemat quote states... "engine wise 05-06 LGT and 04-06 STi are... same long block." But a few sentences prior, it states the heads are different... 04-06 STi uses AB640/910, not same as LGT?

 

 

Kcsubaru.com/showthread.php?4288-All-EJ255-Engines-are-NOT-created-Equal

 

Additionally, valve lash to be set at...

 

Per Subaru:

Intake.... 0.0071 to 0.0087"

Exhaust.... 0.0130 to 0.0146"

 

Per everyone else:

Intake... 0.008"

Exhaust... 0.010"

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Read my click here link in my sig to see about putting a ej257 short block in.

 

It's hard to find a car like these that offer the same bang for the buck.

 

It's been a few years now so I guess I can say, my machine shop bill was $1200 for everything they did for me, understand I've spent a lot of money there over the years and they are old family friends.

 

If you have a plan and do it right. the car will give you back years of enjoyment. I can't tell you how much enjoyment my wagon gives me. It also still surprises me every now and then with how quickly it gains mph.

305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD).  CHECK your oil, these cars use it.

 

Engine Build - Click Here

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Not that I do not believe you, but what necessarily makes factory hard on the valves?
The factory tune makes some compromises, presumably for emissions reasons. The problem is that it can run too lean in boost for too long which raises exhaust gas temperature. High exhaust gas temperatures can lead to burned valves and also problems controlling detonation.

 

You don't have to take my word for it. There is clear evidence in the data logs people have done over the years that have been posted here and other places online. People want to know why they have burned valves or damaged pistons, so they have investigated.

 

I'm pretty surprised at the numbers you posted since you don't have that many miles on the engine.

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Not that I do not believe you, but what necessarily makes factory hard on the valves?

 

The factory tune makes some compromises, presumably for emissions reasons. The problem is that it can run too lean in boost for too long which raises exhaust gas temperature. High exhaust gas temperatures can lead to burned valves and also problems controlling detonation.

 

You don't have to take my word for it. There is clear evidence in the data logs people have done over the years that have been posted here and other places online. People want to know why they have burned valves or damaged pistons, so they have investigated.

 

I'm pretty surprised at the numbers you posted since you don't have that many miles on the engine.

 

 

Yep, the best I did for my 2005 GT wagon was get it on Cobb AP Dec 8 2004. The car had 8000 miles on it. When I had the heads rebuilt at 154,000 miles May 2012, the machine shop told me, mine was the first set of these heads they had every seen that didn't need a valves.

 

When I first met my Tuner, Mike of Tuning Alliance in 2008 he told me what he learned from having his brother 2005 LGT on his dyno and playing with it. He found the timing flaw that can/will cause burnt valves and piston damage early on. He call Tray Cobb and discussed it with him to verify what he was seeing. They know how to fix it.

305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD).  CHECK your oil, these cars use it.

 

Engine Build - Click Here

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I fail to understand the burning of valves. I cannot recall what material they are exactly but I thought all that could burn up would be more carbon deposit which just builds up and causes overlap to be more pronounced?

 

Is there a simple head rebuilt kit with oversized valves? I haven't had the opportunity to look at some internal pictures but do these not have regular springs and roller rockers and what not?

 

Will look within a few hours and post whatever interesting info I can find...

 

To run a rich cobb tune would be safer than a proper dyno tune necessarily (if mods match tune)?

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The valves are steel, sometimes they are hollow and sodium filled. The problem is due to heat, especially for the exhaust valves because they are heated by the exhaust gas leaving the cylinder. Valves do not have a lot of time to cool and very little surface area to transfer heat away. What happens is that the valve locally overheats, weakens and distorts at the edges and does not seal as well. This allows hot exhaust gas to escape at the edges of the valve and this forms hot spots. This gradually erodes the metal and wears it away.

 

Fixing this doesn't really require oversized valves. A machine shop will clean the heads, remove the valves, grind the ones that are good and replace the ones that are bad.

 

The cause is partially the tune not running rich enough to keep cylinder head temperature down. Another contributing cause is that valve clearances gradually tighten up as the engine gets more miles. Insufficient valve clearances mean the valves do not seal completely and/or cannot transfer enough heat away.

b-valves.jpg.e5ed0794bea380108be4da84b83500fe.jpg

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I assume most people have the block surface milled while there doing this?

 

Yes, also ARP head studs.

 

I would you'd be fine until Spring time. Plan you steps over the Winter.

305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD).  CHECK your oil, these cars use it.

 

Engine Build - Click Here

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In regards to bottom end rebuilding, are there any suggestions or specific points for improvement?

 

The vehicle will never see over 400 flywheel horsepower, as I'm sure building the 5eat will be expensive in itself... just looking for a consensus if I should just rebuild the heads or if it is worth it to just do an upgraded crank, new bearings, pistons, etc.

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Most of us get a new ej257 from Heuberger Subaru, a Vendor here for about $1700 and gasket set for your year car.

 

Read my click here link in my sig. My ej257 came from my local dealer.

305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD).  CHECK your oil, these cars use it.

 

Engine Build - Click Here

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Have a machine shop check the heads over, which is a rebuild and cleaning, see if they'll can the oil pan and valve covers too. You'll see in my thread, they assembled the long block for me.

 

Well worth the cost. They do that kind of stuff all the time.

305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD).  CHECK your oil, these cars use it.

 

Engine Build - Click Here

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Part of the problem will be that I enjoy taking things apart. Not so much putting together haha.

 

I will need to find a place that's reasonable to rebuild the heads. I can put the heads back on and start transferring parts easy. Only difficult part will be setting valve lash.

 

Any idea average cost to rebuild heads?

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Any idea average cost to rebuild heads?

Depends somewhat on your location. It will also depend on how many parts have to be replaced. You can check around. Most machine shops have a standard price list.

 

Total off-the-cuff guess would be in the $300-500 range.

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Thank you, I will search around and start compiling a parts list. P0420 keeps appearing so I may purchase an accessport and just load a stage 1 and STi up pipe while letting it go.

 

I guess it is hard for me to see the minimal amount of oil consumption but still trying to purchase a short block. Then again, 122k miles is not necessarily young.

 

Most people set valve lash with motor out of the car and have to recheck it within the vehicle? Doesn't seem easy to do with the motor in, but it seems it has been done.

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After looking into a few options, it seems that just due to ringland failures, and a 280-300whp goal, it may just be best to find a prior rebuilt engine, OR rebuild my block with a heat treated and/or nitrided crank, forged pistons, and heads rebuilt. Issue is, fuel pump and injectors will be in order, and a vf52, and a potential new upgraded valve body for the 5EAT... That seems like... 6k-8k.. Oh joy. The prices to just do it right the first time..

Now.... to start the emailing list, and the searches.

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Wasted -

 

I just went through this on my LGT 12 months ago. 115k miles, owned since new, when I discovered low compression on one cylinder. Other than poor gas mileage, the car ran great. Since I'm in the same camp as Max Capacity (the LGT wagon is a very special car) I chose to goto Stage 2. Unclemat and I did all the disassembly/reassembly except for the head rebuild.

 

The cost for that will obviously depend on where you're located. I used a engine builder who rebuilds for one of the best Subaru tuners in the Boston area where I am. No valves needed replacement and I supplied the new valve seals, so the bill was $900.

 

According to this builder, compression loss most often starts with the valve stem stretching. Once stretched, the valve doesn't fully seat and the edge erosion that Miles described begins.

 

The bare minimum parts to fix the compression (head rebuild aside) probably isn't that much. It's all the "while you're in there" other things that will add up... ;)

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