Burnt exhaust valve replacment

[free5ty1e]

Hey guys - long time.

Both the silver and white Legacy Turbos I've got here seem to have a burnt exhaust valve in cylinder #3 (last in line for fuel). I've suspected this for a while, and am thinking about doing something about it.

I've never had the heads off of a Subaru before, so this is all pretty new to me. I understand that it is possible to barely remove both heads with the engine still in the car. Is this true? How about just valve covers? It is an interesting layout.

Should I get a new set of head bolts from Subaru? Or is there an aftermarket source that this board generally trusts for these?

Is it possible and/or recommended for a 3-angle valve job to be done while I've got the heads off? Also, how often are replacement valve guides and seals needed? Is it generally recommended to do the valve job if I just have a burnt valve that needs replacing?

Do our heads warp easily? To my knowledge, neither of my EJ22Ts have been overheated. But then again, I did not own them since they were new, so I have no way of knowing.

Is there a source for reconditioned heads, would this be cheaper than working mine? I'm not looking for a port/polish, or any port matching, I just want my valves to seal like they should.

Is the special cam sprocket tool listed in the FSM required to loosen the bolt, or can I rig something up?

Are there any left-hand / backwards threads anywhere along the way I should be aware of (so that I don't tighten something really hard with an impact or breaker by accident)

Any other special tools I will need during this process? I know the head bolts are 12-point 14mm. That's about all I know. Thank you.

[entirelyturbo]

How do you know the valves are burnt?

The only way I think you can tell that a valve is burnt would be to do a compression test and find compression down in ONLY that cylinder...

And one of the best ways to burn an exhaust valve is to have an exhaust leak either right at the exhaust manifold gasket, or very close to it.

Nonetheless...

I've never had the heads off of a Subaru before, so this is all pretty new to me. I understand that it is possible to barely remove both heads with the engine still in the car. Is this true?

It's harder, but possible. Several people on this board have R&R'ed the heads with the engine in the car.

Should I get a new set of head bolts from Subaru? Or is there an aftermarket source that this board generally trusts for these?

You should probably get new Subaru head bolts. And be sure to tighten them exactly the way a Haynes or FSM says, otherwise you will almost assuredly have future problems.

Is it possible and/or recommended for a 3-angle valve job to be done while I've got the heads off? Also, how often are replacement valve guides and seals needed? Is it generally recommended to do the valve job if I just have a burnt valve that needs replacing?

Couldn't hurt

Do our heads warp easily? To my knowledge, neither of my EJ22Ts have been overheated. But then again, I did not own them since they were new, so I have no way of knowing.

If you do the valve job and all that on the heads, tell the machine shop to check the heads for warpage.

Is there a source for reconditioned heads, would this be cheaper than working mine? I'm not looking for a port/polish, or any port matching, I just want my valves to seal like they should.

Only if your heads are warped bad enough that they can't be milled back into spec would you need new heads.

Is the special cam sprocket tool listed in the FSM required to loosen the bolt, or can I rig something up?

Loosen the bolts on the cam sprockets before you take the timing belt off

The rest of the stuff I dunno. I've actually never removed any Subaru head, so I can't say...

I'd say double-check on the burned valve thing though...


Oh, and by the way, you weren't driving down Colonial Drive this past week were you, going to Cycle Riders? If that was you in the white SS, then I was the guy behind you in the white wagon with the turbo bumper...

[free5ty1e]

Hey subyluvr whats up? Nope that wasn't me; I've never been to Cycle Riders. I haven't really driven too much on Colonial lately; I'm in the Altamonte Springs area now.

Anywho - yes, my compression tests on both cars showed all the other cylinders at around 140 PSIish, and cylinder 3 was under 120. Almost at the service limit.

I was mainly looking to get a feel for what usually is found in an EJ22t with almost 150k miles; are the heads usually warped? Valve guides need replacing yet? I'd sure like to just replace the burnt valve and not have to find a machine shop...

[All_talk]

Might wanna do a leak down test, that will tell you where the compression is going.

Gary

[free5ty1e]

Well, I find it very suspicious that both of my EJ22t engines show almost identical results from compression tests, and the fact that the cylinder with the lowered compression is the last inline for fuel reeeeeally makes me think its a burnt exhaust valve.

What additional information would the leakdown test provide me with? Never done that before, no idea how even. Wouldn't I still end up with a diagnosis of a problem inside the head...?

OK, how about this; anyone who's had the heads off an EJ22t, what wear is typical to find and at what mileage did you check? Was it necessary to send to a machine shop before re-installation? I'd just like to have a better idea for what to expect from these engines. If it ends up being too involved or expensive, I will just have to wait until I can afford it, and deal with the uneven compression.

I'd be working in my friend's home garage, and will be taking the heads off with the engine still in the car. So mainly, if it's highly probable that we can do everything in his garage then we'll do it; finding a machine shop with a reasonable rate that's willing to work Subaru heads might not be too easy, and I'm not prepared to drop hundreds on this right now. Especially since I've got two sets of heads to do this to.

[evolutionmovement]

Wear should be almost zero. That's an EJ22T @ 83k and a beat on long oil change N/A @ 246k.

A leak down will tell you where the problem is. If you get air from the PCV, you have a ring problem; from the exhaust, a bad exhaust valve; from the intake, a bad intake valve.

Steve

[free5ty1e]

I see. Isn't that not an accurate test for the rings though, without the engine running and oil circulating and such? Besides, I don't have access to that equipment and I'm trying to keep the budget to a minimum here. I'd say I'm pretty bound for valve replacement of some type here, and of course all gaskets and bolts along the way. Probably an HLA or two, from what I understand.

I'm going to start going through part numbers and locating sources for all these parts. I'll post the list too so it will be easier for others to do the basic R&R of the heads.

Since I've got two cars, I'll just remove one set of heads and see what parts are needed, and take my time. Then, once that car's running again, I'll remove the other's set of heads. No down time. That helps.

So Subaru did a good job on our heads, as far as longevity, necessary maintenance, and wear is concerned?

[evolutionmovement]

You're supposed to get the motor warm before doing the leak down. If you could get just a threaded valve to fit the spark plug hole with a barb on the other end, you could just get a cheap bike pump to hook up to it and pump air in. All you're basically doing is pressurizing the cylinder with air and listening for leaks. The tool's a hand pump anyway. You should be able to get an adaptor to fit the plug hole at a competent auto parts place for a few bucks and a cheap bike pump for a few more.

It's up to you as it sounds like you have to disassemble it anyway, but just for future reference, it might not be a bad thing to make.

Steve

[mikec]

Was it Vikash that once talked about drilling out a spark plug to make an adaptor for doing a leakdown test? I know I read the suggestion somewhere. Not sure how feasible it is...

[Matt Monson]

#1 Pull the engine. You will find it much easier. I see no point in ever working on one of these engines in the car. And since it isn't your only car, you don't have some sort of time crunch forcing you to do this. It's easier on your body, and you can inspect a lot of other things while it is out.

#2 There is no reason to buy new head bolts. I have always reused them, and having consulted with engine builders at Cobb and Crawford, they tell me they do the same thing.

#3 Buy all new exhaust valves if you are going to go to the trouble of doing this work. Also, be sure to bleed all the HLA's and replace any that won't hold pressure after bleeding.

#4, if you don't have a strap wrench, knock loose both the crank pulley with the engine in the car. The cam pullies are a little more tricky, and I generally use a flathead screwdriver to lock the flywheel in place while I crack them loose. If it is an auto, it's a little more tricky to lock the plate in place. You have to do it through the hole in the top of the block. If you have an air gun, they come off really easily and this is all mute...

[professor]

if you squirt a little oil into #3 and repeat the compression test, and find that it improves quite a bit for a short while

then you have worn rings / beat piston / cracked rings etc not a burnt valve

if the reading stays the same after the oil is added then its likely valve-related

use about a tablespoon of oil

[evolutionmovement]

I'm going to second Matt with pulling the engine - the time it takes to pull it or at least lift it clear of the frame rails will save you more hours and lots of swearing in the long run. Pulling it sounds much worse than it is. It may be a good idea to try to loosen the head bolts while the engine's bolted in, though.

Steve

[entirelyturbo]

Matt... reusing head bolts???

I thought that the funky torquing procedure for head bolts was because you actually stretch the bolts out slightly on the first part of it, and then torque them to spec in the second step. Therefore, once the bolts are stretched, they are good only that once and must be replaced if the heads are removed...

I realize you've done way more rebuilds than any of us, so I'm not trying to discredit you. But these are official Subaru procedures!

[free5ty1e]

This is good stuff, thanks guys.

I also was under the impression from the FSM that the head bolts would only be good for one use; they get torqued and then angled past that to stretch, right? That's cool if I can reuse them though.

The pre-compression-test temporary ring lubing sounds like a nice alternative to making a leakdown tester. I think I'll try that out.

Pulling the engine from the car still doesn't sound like it's feasible in my friend's garage. No hoist, no engine stand, not much room, etc. I mean, we've gone and rented a hoist before to replace the engine in the old Saturn, but man that was not easy. (damn boat anchor)

[Matt Monson]

To each their own. I have talked to a lot of people about this, and most of them reuse. I even discussed it with our shop mechanic one day who has been building engines for 40 years. He said that if the bolts aren't showing any signs of fatigue (he mostly works on Porsches and because of their placement they exhaust side studs can rust) then there should be no problem reusing them. There was a thread about in on NASIOC a few months back. All the guys who came to this from US domestic muscle were saying, "replace them, replace them" but all the guys from strictly an import background were saying you could reuse them.

In short, some people consider it cheap insurance, I consider it a waste of money. Make your own decision accordingly. Do what you feel comfortable with...

[evolutionmovement]

Thing is, it's not that cheap insurance. I think I paid about $100 bucks for them at subaruparts.com. Reusing them is a nice chunk taken off the bottom line if it's not a problem.

Steve

[napphappy]

The FSM is always pretty clear when you need to replace something. They use bold print and say "CAUTION". Nowhere could I find it to say to replace the head bolts.
Thats enough for me.

I think Matt is right. Its the Detroit Iron guys that are always stuck on replacing them.

Im another who has never replaced them, and never had a problem(with the HGs anyway).

[vrg3]

Can't you just check the threads with a thread pitch gauge (or even another bolt with the same thread pitch) to see if the bolt has stretched or not?

[professor]

it is the plain-shank part of the bolt that stretches, it is made to stretch there to keep the distortion away from the threaded portion. The bolts are actually cleverly heat treated, or tapered, such so the threads are stronger than the shank. I don't know of any way to tell if they are bad other than obvious signs like a crack or the head missing (bmw 325's do this !)


If you use them again, and follow the same procedure, you may be double-stretching the bolt. if the stretch is all in the elastic part of the stress-strain curve for the bolt (reversible), you will be fine. If not, you may not be.

btw the bolts stretch so that the clamping force is much more even with thermal expansion, since aluminum expands a lot more than steel does with heat

if it has proved to not be a problem, go for it. I wouldn't but that's just me