Burnt valve, looking for options
Hey guys! First post, and unfortunately it's not a good one. New to Subaru's, but not cars in general. I work as a tech for Lexus.
So my mother has an '05 Lgt, just over 118k. A few months ago it threw a p0301 code, and started to idle a little funny at cold start. I figured it was a coil and would get to it soon enough. Cleared the code, and it stayed away for a few months. About 2 months ago, the code came back. In this time, the idle had gotten significantly worse. Still totally drivable, but it felt like the motor mount were going back or something. Just a constant slight rumble. Cleared the code again, and bought some coils. About 2 weeks ago, the car started REALLy bucking at idle. True misfire. Felt like a machine gun. So I bumped up the priorities and finally threw the coils and plugs in. No difference. Bummer. Checked spark, good. Checked fuel, good. Check compression, BAD. Cylinder 1 had 40psi, compared the to other 3 that were around 200+. Went further and did a leak-down test, and air was just pissing out the exhaust. After about 5 minutes of deliberation, it was decided the motor had to come out.
Pulled the motor friday night, and found a burnt exhaust valve in cylinder 1, just as indicated by my tests.
So now my question is, where do I go from here? I need some opinions/advice/critique since I'm so new to these motors. My plan is to buy 8 new exhaust valves, and have the machine shop install them, and grind or lap the seats. Also clean and inspect all the intake valves/seats.
- I'm assuming the lash needs to be reset with the new valves installed? The little buckets look like a total pain in the ass to set up.
- Are there any aftermarket exhaust valves that are stronger? Or should I buy the OEM sodium filled ones again?
- I've heard horror stories about the 2.5 head gaskets, was this straightened out by 2005? I'm planning on using the OEM 10105AA720 gasket kit, and want to make sure everything is kosher.
- The turbo looks to be in great condition. No noise or abnormal play/wear inside. I've heard the VF40's can be rebuilt as long as there's no wear or play in the shafts. Should I look into a rebuild kit or leave well enough alone? At 120k I'd HATE to get it all back together just to blow another $500 on a turbo next month.
I also sent the injectors out to witchhuntperformance to be cleaned and tested.
Here are some pictures from the night for shits and grins.
Here's the valve.
And how the poor motor sits now :(
subscribed for info.
Injectors could be source of burnt valve.
If all other valves are ok, replace just the bad one and shim just that one. You'd be best off taking the head somewhere that does them alot. They will have a collection of buckets to choose from. They cost about $25 each and sometimes it takes 2 or 3 tries before you get the right set of buckets. Stock valves are just fine.
How did you get a 200+ psi compression result?
If you are mostly stock, use stock headgaskets. If you are going to rebuild the motor yourself, get headstuds instead of the stock bolts. All you need is a torque wrench to install them. (stock bolts cannot be re-used and are tightened by torque-angle instead of just torque.) If the car is stage 2 or higher, go with something like Cosworth gaskets and switch to headstuds for sure.
I'd hate to see a turbo with 120k go back on a motor like that. It's a tough call whether to re-use or not.
I am far from an expert but I believe 200psi is far above what it should be when built. 40 on the other hand is definitely bad.
200 psi - that would be great for a NA engine running high octane fuel, not so great for a turbo engine. (Unless it's a low compression diesel...)
But then - some compression tools has a pretty bad precision, so if a cheap tool was used I would just file the figures under bad scale tool.
It's not the valves that are the problem, it's the factory tune. It is well known that the OEM map has a flaw and can cause burnt valves.
That's from my Tuner, he found the flaw a few years back.
FWIW, I'd let the machine shop rebuild the heads and pick them up completed. Oh that's right, I think the cam's have to come out to install the heads.
I just let my machine shop give me back a long block.
You can use the stock valves, just get the car tuned soon.
The stock HG's are fine, I did have my machine shop install ARP studs.
Most guy's will send the vf40 off to Brian at BNRturbos and get a 16g that he sells.
I just went with a vf52.
Better and more even crush on the HG.
Most guy's I know wouldn't do a engine without upgrading to ARP studs.
Hey guys, sorry haven't updated in a few days I've been super busy between work and trying to tackle this headache. I tore into her a little deeper. The short block look amazing. Crosshatches still on the cylinder walls, no glazing or scoring. The bearings were just as good, no significant signs of wear. I also cleaned off the domes of the pistons. They had a decent amount of carbon buildup, but nothing I would deem abnormal for a 120k mile engine.
I dropped the heads of the the machine shop today. After speaking with two subaru specialty shops near me (one of the being AndrewTech, don't know if they're known on here), it sounded like one valve (or two) valves were all I needed. The machine shop I took them to has been around for two generations, and has a VERY high reputation. I've had multiple flywheels done there, and a jeep block bored before. Trust is defintiely established. I told him to check out both heads, let me know the condition of all the valves. He said the burned one really wasn't bad at all. He said he could grind the partner exhaust valve of cylinder one fine, but recommended replacedment just in case it had been overheated or mushroomed or weakened etc, from the first valve getting roasted. He would also set the lash of all the valves with the heads off the block. I questioned this, after reading a few people saying it MUST be done on the block. He said it's not a big deal, and they've been doing it for decades without issue.
So a few misc. questions I have now are:
- Is there anything else I should be replacing while the motor is apart? Oil pump, any internal seals that won't come with the gasket kit, etc.
- Should I replaced the trans (automatic) input shaft seal? The torque converter pulled out about 8 inches when I was removing the motor. I didn't realize it has this gnarly long shaft attached to it, and it was probably resting all it's weight on the seal. Not to mention getting pushed/pulled/jostled around during the motor lift.
- I'm hearing very conflicting reports on the head bolts. Some say replaced them, and get studs. Other say don't even bother unless you're going performance-minded. This is a bone stock rebuild.
- I'm still researching what to do about the turbo. I need this to be as reliable as possible, but also as cheap as possible. A replacement turbo looks to be out of the budget so I'm still pondering a rebuild.
Keep the brainstorming and critiquing coming guys, and thanks thus far!
There's my thread. Lot's of good info there.
If you plan to keep the car, I recommend ARPstuds for the heads.
Oh Yea, nice to see you know how to work on the car.
Keep us updated.
You have to buy new hardware for the heads either way. Either new stock bolts, or for a little bit more, you can switch to studs.
Lash does not need to be set with the head torqued down.
Got a few more things cleaned off today. The pistons and tumbler valves were pretty dirty so I gave them a wash.
Here's a closeup of the burnt valve. I didn't realize my pics were so small in the OP
I'm thinking I'm gonna go for the head studs. Better safe than sorry right.
- In regards to the turbo, I'm still up in the air on this one. I'm trying to keep everything bone stock. I emailed BNR about a rebuild, still waiting for a reply. I also ordered both OCV valves, as I've been reading their failure can blow a turbo too. Tomorrow I'll pull out the filtesr in the banjo bolts and inspect them as well.
- My gasket kit came in today. Holy hell there is a lot of stuff here. I'm gonna put a pic up of all the stuff that I don't know the location of. Can you guys tell me where some of these pieces go? Especially that funky foam.
He could use a set of vacation pics if anyone has 2005?
|All times are GMT -6. The time now is 06:02 PM.|