05 Outback XT Engine Rebuild

[Flatfour02]

Hi folks, I've got my XT's engine out right now. Heads are off, and the cylinder walls look impeccable! I mean not a SINGLE vertical mark on any of the cylinders. It's got over 130K miles on it.

 

Now, moving on to the bearings. If I should split the case halves, and find that everything seems okay, check the bearing clearances and they are all okay, should I go ahead and just replace the bearings with a set of OEM since I'm already here? Or should I leave well enough alone? Will replacing seemingly good bearings with a new stock set require any machining? What do you more experienced builders suggest? Thanks.

[Flatfour02]

Also, how about piston rings? Like I said, the cylinder walls look great, but should I replace the rings just because? Thanks again.

[Darth SpecB]

Personally I would replace the bearings with oem or king. It should not require machining if you get king bearings but the size you need will need to be determined preferably by a bore gauge and micrometer. If not then use plastidip, it should suffice as long as your not shooting for more than 450whp+

 

Unless your compression test results are flawless might well replace piston rings, since your already in there just as preventive maintenance ie. less oil consumption, better compression, less chance for blowby.

 

Sent from my SAMSUNG-SM-G900A using Tapatalk

[Max Capacity]

You'll need to hone the cylinders for new rings. Also open the end gap a couple of .001's, there are threads about it.

[Flatfour02]

Welp, I pulled piston #2 and #4, and they both have failed ringlands. There also appears to be some scoring and foreign contamination on the bearings. Looks I need new everything... Machine shop we go I guess.

[fahr_side]

If you're at 130k it's really unlikely the bores are in tolerance for either roundness or parallelism. Just rebore while you're in there.

[StkmltS]

Yup, you may as well put in new bearings and rings (+ a hone). At this point labor will be most of your cost. You've already saved a ton of cash having made it this far doing it yourself.

[birkhoff]

You COULD rebore for oversize pistons, but unless you have access to a machine shop that has a torque plate and some experience with these blocks, you may end up with a not so great job. With the case halves split, and with the heads off, the cylinders tend to go out of round. Bore them round and when you put everything back together . . . who knows.

 

If the walls look in good shape, one might assume that the original bore is reasonably intact. If you accept that, just have the machine shop do a good plateau hone and give back to you to put things back together with new pistons and rings. An experience operator on a honing machine can clean up much the unevenness at the top and bottom of the stroke (again, assuming you can't really see it in the bores right now) but leave existing oval intact. A machinist like this will appreciate having the pistons on hand to fine-tune things as they go.

 

You should know that `new' stock pistons are available for $25 a hole (see Stkmilts' thread for sources). Get a set that matches the grade marks on the top of the block. Unless you have a great set of bore gauges, in which case you could try to fine tune things by matching grades with actual hole size. Difference between grades is a few tenths -- this can sometimes be finessed with the hone.

 

For the mainline, while it is best to measure with a bore gauge first and order bearings accordingly, you might get by with one set and no measurements. Look at the 5 numbers on the top of the block. If they are a bunch of 2's, experience here suggests that getting a set of 0.026mm oversize will likely return you to to almost stock clearances. Plastigage is your friend for this shortcut.

 

Fitting the rods seems to be a non-issue with these engines. Get a set of STD rod bearings and you are likely to be good.

 

Finally, check your crank journals carefully. A new crank can be had for about $300 and at that price, is almost a 'consumable' in the rebuild world. A new crank will deal with about half of your tolerance issues on the mainline and rods. Personally, I wouldn't bother to grind or even polish a Subaru crankshaft at those km.

 

There are all sorts of ways to spend big money on this stuff and end up with an unsatisfactory outcome. However there are some good threads proving that by concentrating on some boring, old-time basics, you have a good chance to have a successful rebuild without going overboard on parts and fancy machine work. Pay the machinists to do what they are good at, use stock pistons and rods, be patient on the assembly and you can have a good as new short block for a fraction of the cost.

[Flatfour02]

Well, I've got a Mitutoyo bore gauge, and a Starrett 3-4" micrometer, so I've got the tools to check the bores. As previously stated, the cylinder bores look amazing, not a single vertical scratch on them, (this kind of surprises me, every single piston had a blown ring land, and no freakin scratches on the bores!?) so I'm really hoping they're not warped. I'll be checking them probably this weekend. I already checked the block to head mating surfaces on the block with a straight edge and .0015 feeler gauge, and it passed that test with flying colors. I believe the spec is .002. The journal bearings clearly have foreign material gouged in them, but it doesn't seem like they are spun, the block bores seem to have been left untouched, but that will require further investigation I suppose, as I don't fully know what it would look like had they spun and caused damage to the block. So, next week, I'm going to bring the block in to work and clean it. Afterwards, I will bolt it back together, and measure the cylinder bores, "and the journal bores" (don't know if that is the technical term) to check for out of roundness, and size. I will most likely post those numbers on here, for piece of mind. I'm guessing from birkhoff's comment, that I should just go ahead and grab a new factory crankshaft. Keep in mind, this is not exactly all about saving me money, I could have easily just grabbed a Subaru block for $1800 and swapped it in myself. I decided to take this rebuild on as a personal "hobby". I do know how to operate a mill machine, and I do in fact have access to one, so should the cylinder bores need honed, I'd hope to be able to do it myself. Any tips on the machining side of things are greatly appreciated, and I appreciate the info given to me thus far. Thank you guys.

[birkhoff]

Once you clean it up, here is what to expect:

 

Cylinder bores will be out of round; worse at the top than bottom. Because things change when you mount the heads, there is not really much you can do about it, nor should you. Just go for a hone unless the min diameter is too large for stock pistons.

 

Base bores on the mainline will be out of round, especially #2, 4 where the webs are thinner. There is no spec for this bore. I would estimate it off the parting line if you want to know what it should be. Make sure you torque case halves to spec before measuring -- it makes a big difference. Plus, it is good practice for when you do the final assembly

 

Crank journals will be out of round. Given that the spec running oil clearance is 4 - 12 tenths, combining the out of round bores and crank journals, it is difficult to hit anywhere in this window. By getting a new crankshaft, you have journals good to about 1 tenth in dimension and oval. That is a big help. Plus, if your bearing faces were messed up, you'd at least need to polish the crank, which partly balances the cost of a new one. And polishing doesn't fix oval.

 

Get hold of the FSM and write down all the dimensions before you start. You may be surprised at how tight these engines are built.

 

Get the machine shop to do the hone. They have expensive machines for this that can make your cylinders nearly like new. A good hone is why your cylinders look so great in the first place. A good hone will make sure the cylinder walls hold oil properly and the rings seat. Finally, it is not expensive. 20 bucks a hole, maybe less.

 

If you do engage a machine shop, I wouldn't bother cleaning the case. Just get the measurements that you need to make your decisions and hand it to the shop. There is no way they are going to put a questionably clean block into their $50,000 hone -- they'll run it through the dishwasher first.

[StkmltS]

Dishwasher smishwasher. Toss the block down in your front yard and go at it with a pressure washer! I'm only halfway joking, because that's how I cleaned my block. Well, and I rinsed it in the bathtub afterwards just to get the grass off

[birkhoff]

Dishwasher smishwasher. Toss the block down in your front yard and go at it with a pressure washer! I'm only halfway joking, because that's how I cleaned my block. Well, and I rinsed it in the bathtub afterwards just to get the grass off

 

Not in January you didn't!

 

Unless FlatFour02 lives in California or Florida, this is not the best time of year for water sports.

[Max Capacity]

X2 for letting the machine shop do what they do best and better then you can do.

 

I'd even go as far as letting build the SB and set the valves if they will do that for you.

 

Again let the experts do their job.

 

My machine shop gave me back a long block with timing belt installed and oil pan on.

[mwiener2]

These motor are too cheap to bother machining. It's one more area for failure. Just buy a new shortblock, built or stock. Or at least start with fresh case halves.

[Max Capacity]

These motor are too cheap to bother machining. It's one more area for failure. Just buy a new shortblock, built or stock. Or at least start with fresh case halves.

 

 

Sometimes it's hard for people to believe that...I'm glad I did a new ej257.

 

Some of the best advice the machine shop gave me. OP, the machine shop told me for my hp goals, I was better off buying a new ej257 and having them rebuild my heads.

[Flatfour02]

Thanks for all your input, friends. Keep in mind, this build is more for the experience of building an engine for me. If I build it and it doesn't run, I'll go ahead and shed a few tears, then buy a SB from Subaru. But for now, I'd like to go through the steps of a rebuild simply for the experience of doing it. I have heard this same thing from "Dr. Subaru" at Orbach's Automotive in Denver PA. A lot of the Subaru folks around the area don't trust anybody but him with their Subaru's, and when I called him and asked him for a reference for a good machine shop, he told me to throw it out and buy a new SB lol. But we'll see how it goes... If my cylinders are obviously too far out of spec and I have to get it machined, I'll probably just get the SB from Subaru. Time will tell, and I'll post my measurements on here by the end of next week.

[StkmltS]

Thanks for all your input, friends. Keep in mind, this build is more for the experience of building an engine for me. If I build it and it doesn't run, I'll go ahead and shed a few tears, then buy a SB from Subaru. But for now, I'd like to go through the steps of a rebuild simply for the experience of doing it. I have heard this same thing from "Dr. Subaru" at Orbach's Automotive in Denver PA. A lot of the Subaru folks around the area don't trust anybody but him with their Subaru's, and when I called him and asked him for a reference for a good machine shop, he told me to throw it out and buy a new SB lol. But we'll see how it goes... If my cylinders are obviously too far out of spec and I have to get it machined, I'll probably just get the SB from Subaru. Time will tell, and I'll post my measurements on here by the end of next week.

 

I love it!

Have you looked through my rebuild thread? Not to toot my own horn, but (tooting own horn to follow) based on what you just said I think what's in my thread would be particularly useful to you as a reference. Feel free to send me a text or call if you get in a bind and you want a second opinion. After the FSM, this forum and the people on here will be your greatest resource.

[Flatfour02]

I love it!

Have you looked through my rebuild thread? Not to toot my own horn, but (tooting own horn to follow) based on what you just said I think what's in my thread would be particularly useful to you as a reference. Feel free to send me a text or call if you get in a bind and you want a second opinion. After the FSM, this forum and the people on here will be your greatest resource.

 

Indeed I have looked and actually favorited your thread sir. Very well written with lots of good information. I've already referenced it a few times, and will most likely be doing so again.

[Flatfour02]

So, I've torqued the case halves back together and took measurements on the cylinder bores today.

 

#1 Top: 3.9177, 3.9177, 3.9177

#1 Bottom: 3.9179, 3.9177, 3.9178

 

#2 Top: 3.9180, 3.9182, 3.9179

#2 Bottom: 3.9175, 3.9174, 3.9174

 

#3 Top: 3.9175, 3.9173, 3.9184

#3 Bottom: 3.9175, 3.9177, 3.9178

 

#4 Top: 3.9178, 3.9175, 3.9177

#4 Bottom: 3.9174, 3.9174, 3.9174

 

Also, the case halves are BBBB, and the pistons inside did match that.

 

So from what I've read, the factory Subaru spec is this:

 

Taper- Standard= .0006"

Limit= .002"

Roundness- Standard= .0004"

Limit= .002"

 

Looks like in some areas I am just outside of the "standard" but always very well within the limit.

[birkhoff]

Why three measurements in each position? Normally you measure perp to the piston pin and parallel to pin. The difference is the out-of-round. The reason is those two directions will most likely show the maximum difference.

 

Taper and out-of-round limit being 5X standard seems a little odd. Where are you finding those numbers? I've not seen them in the FSM. Remember that stock PTW clearance is only +- 0.0004

[Flatfour02]

Why three measurements in each position? Normally you measure perp to the piston pin and parallel to pin. The difference is the out-of-round. The reason is those two directions will most likely show the maximum difference.

 

Taper and out-of-round limit being 5X standard seems a little odd. Where are you finding those numbers? I've not seen them in the FSM. Remember that stock PTW clearance is only +- 0.0004

 

I just remember being taught to take 3 measurements each for some reason. May just be remembering it wrong. Those specs I found in a forum somewhere, I'll have to look for it. Do you know of any set limit that Subaru has come up with for taper and out-of-round? I imagine when sizing pistons, you go off of the smallest measurement you get per cylinder? I would think smaller would be the safer option at this point.

[birkhoff]

With OEM pistons, I don't think we've heard any compelling arguments here to suggest that shooting for anything other than factory PTW is desirable. That means ZERO PTW with a range of -0.0004 (piston bigger than bore) to +0.0004.

 

So what the heck does this mean, when measurements are all over the place? There is a piston grade point perp to the pin and about 38 mm down from the crown. Measure your piston there. The corresponding measurement in the bore is what you want to compare to, and you are shooting to get it pretty darn close to the same (+- 0.0004)

 

So, for example if your 2n'd measurement in Cyl #2, top, was taken perp to pin, then you would want to have a piston close to 3.9182 at the grade point. That means you would select an A-grade piston for that bore. If all measurements are correct, it will run with about 3-4 tenths clearance since A-grade pistons max out at 3.9179 at the grade point (the ones I have measured tend to land about in the middle, in fact, so maybe a bit more than that). Not accounting for any changes due to the hone, of course. A couple of snips attached from the FSM should make this clear.

 

In practice, since you can't change the size of the pistons, you tweak the bores during the hone. The machinist will want to have the pistons in hand and whatever requests you make for PTW numbers, and then they will hone to fit. It doesn't take long to remove a couple of tenths with a power hone.

 

Given the numbers you report, I would get a set of AAAA pistons as pulls, then take the case halves and pistons into the machinist. They will fit the bores on the hone, number the pistons and send them back for you to assemble.

 

Easy-peasy and you will have a good result. Of course, run your plan by the machinist before you buy the pistons, just to be sure.

[Flatfour02]

So, with a PTW clearance spec of +-0.0004, by my measurements there, I should be able to drop stock "A" pistons in (not counting any variation from the hone) all four cylinders, and be within spec for the PTW. As far as the taper and out of round are concerned, the worst measurement is in cylinder #3, where the maximum taper measurement is .0009, which is .0003 out of spec, and maximum out of round is .0011, which is .0007 out of spec. I would be able to expect those differences to get closer to spec with a hone, would I not?

 

Also, the other number on my case halves is 23233. Doesn't that have something to do with the bearings? Thanks very much birkhoff.

[birkhoff]

Yes, an experienced operator can reduce taper (up to a point) with the hone, but less so out-of-round, which you don't really want to mess with anyway since you don't know how much is caused by case distortion that will correct itself once the heads go back on.

 

For comparison, on lower mileage cases, some folks are replacing like with like (grade-wise) and just a light hone. Not fussing much with measuring. With your higher mileage block, it is lucky you can go from B to A on the grades -- it gives a little room to clean up the bores and fine-tune as required.

 

Just make sure to check with the machinist who will be doing the hone before you commit to pistons.

 

The 23233 marks do refer to the bearing shell thickness on the mainline, but nobody seems to know how to interpret them. Is 2 thicker than 3, or the other way around? And how many grades were there? Did they use half shells? If you have a ball mic, and marked the shells as they came out, you might be able to backwards engineer the code. Shell thicknesses are mentioned in the FSM.

[StkmltS]

So, with a PTW clearance spec of +-0.0004, by my measurements there, I should be able to drop stock "A" pistons in (not counting any variation from the hone) all four cylinders, and be within spec for the PTW. As far as the taper and out of round are concerned, the worst measurement is in cylinder #3, where the maximum taper measurement is .0009, which is .0003 out of spec, and maximum out of round is .0011, which is .0007 out of spec. I would be able to expect those differences to get closer to spec with a hone, would I not?

 

Also, the other number on my case halves is 23233. Doesn't that have something to do with the bearings? Thanks very much birkhoff.

 

With honing you may be able to improve the taper if you spend a little more time in the smaller diameter area of the cylinder, but the out of roundness probably won't change. The honing balls on a ball hone push outwards on the cylinder wall and remove a theoretically even amount of material around the circumference. So any area of a cylinder that's out of round will still be just as out of round as when you started.

 

If you hone each cylinder for 15-20 seconds you may not even be able to measure a change in diameter. Honing isn't supposed to be used as a way to make cylinders larger. Think of it more as surface prep than machining. The whole point is in fact to remove material, so obviously you are technically making the cylinders slightly larger. "Fixing" your taper, or making it worse definitely won't happen on accident, so don't be too worried. Youtube is your friend.

 

Don't worry about it too much. You may not be 100% in-spec, but in my opinion a slightly larger cylinder is a relatively minor concern. Will it hinder performance?... maybe, but probably only an immeasurable amount. Will it consume more oil?... maybe, but probably only a couple extra drops per bazillion miles. Will you notice a difference when you're driving the car?... no way.