Andrew's DiySB Rebuild

[birkhoff]

Isn't it the opposite? From my understanding, a tighter clearance (assuming valve shape and stem length are still like new) means that the valve cannot fully close, which would also result in the valve opening more I'd think.

 

Exactly, which means the valves are not transferring heat properly through the seats, hence running hotter than they should and, if bad enough, allowing hot combustion gasses during ignition to contact the sealing surfaces. The extra valve lift is inconsequential, I would think.

[StkmltS]

Let's have an Internet argument. Ready, go!

 

I'll think it through out-loud just for fun.

 

Lash is how much empty space there is between the bucket and the cam lobe, when the cam lobe is fully disengaged, or pointing away from the bucket. When the cam is fully disengaged the spring is able to expand as much as the retainer will allow, pushing the end of the valve stem as far away from the head as possible, and pulling the valve head as close to the seat as possible. The spring is always under compression, so the valve head coming into contact with the valve seat is what limits the spring from fully expanding. That mean that as long as your valve lash is >0, your valve will close.

Edited July 12, 2016 by StkmltS

[xt2005bonbon]

I think your logic is correct. But the question is, how much lash does it take for the valve to stay open? Cause we have to remember that when the engine gets hot, the valve stem probably elongates a bit, thereby reducing lash even more (by how much? I don't know).

[birkhoff]

That is a perfect description and would be the end of discussion if engines ran at a steady 20 deg C. The lash is mostly to compensate for the fact that the overall valve length is longer in a running engine than in a cold one. Plus a little something for wear and margin of error.

 

In older engine designs, lash was also linked to valve open and close time, and overlap, but with independent cams and variable timing, I doubt that has much to do with it anymore.

[StkmltS]

Good thoughts. So if your lash is tight (enough) there's probably some magical point (temperature) at which the valve stem gets slightly longer, effectively reducing the lash to less than 0, and preventing the valve from fully closing. I can buy that.

 

...Although this still doesn't explain why I didn't see misfires when the car was moving.

 

So in my case, and probably yours, our cars have ran for thousands of miles with one or more exhaust valves not fully closing, which has allowed carbon to build up (don't tell Al Gore) on the valve seat. So even after we corrected the valve lash it was too late, there was already gunk between the valve and seat preventing it from ever fully closing. I wonder if a little bit of Sea Foam every X,xxx miles would have been an effective preventive measure.

Edited July 12, 2016 by StkmltS

[StkmltS]

More importantly, you two haven't voted in my painting scheme poll yet.

[xt2005bonbon]

Sea foam can help I'd think, but btssm helps even better . If I see 0 roughness at idle, I am a happy camper. Since fixing the valve clearance on the 05, roughness is always 0 at idle no matter the temperature. And fyi, I also shot for a slightly looser clearance on the exhaust valves (0.37mm instead of the 0.35mm).

[birkhoff]

Measuring mainline.

 

Your bore gauge will need to be set up to measure about 2.520 inches. There is no spec I could find for std bore diameter, without shells. You are looking for oval and differences between bores.

 

Torque case halves together following the spec pattern and values. The latter is really important -- I did some experiments with partial torqued case and found things moving all over the place. I didn't bother with the small case bolts off the mainline. You main want to.

 

Run your straightedge in and look for any rocking in various direction. None? Good. Check the flatness of the fire decks again. That may change when you clamp the case halves together.

 

With bore gauge, check perp to parting line, and then along parting line (not exactly along, since that won't give a good measurement, but angled just off) That will tell you oval. Do this for each bore and write things down. You should find that the bores are slightly wider perp, than parallel due to the crankshaft pressures. The small web bores are likely to be worse than numbers 1, 3 and 5.

How much is too much? I really don't know, but if it is approaching the target oil clearance, you may want to rethink things.

 

It is a good idea to set up a micrometer with some standard value in the right ballpark and frequently check back with it to eliminate drift in your bore gauge. Just like you did with the cylinders, right? I looked over your tables for evidence of drift and nothing really stood out. So either you are really good at this, or you reset your bore gauge a few times during measuring. I have to do the latter. Hot hands I guess.

[birkhoff]

More importantly, you two haven't voted in my painting scheme poll yet.

 

Oh, well, you know me. Mr. Stock. I can't bring myself to paint anything that wasn't already painted.

 

If 'don't paint anything' was an option in the poll, I would have voted long ago.

[birkhoff]

Are you really planning on re-using those pistons? That is an unusual step. There is no skirt coating, unknown ring land wear (maybe you checked that already, but you need a new set of rings to do it) and something else I can't really think of at the moment. You can see I'm not a fan of this part of the plan.

 

There is a set of BBBB fresh pulls on Outfront site right now for $150 which is $50 more than you really need to spend, but they are trustworthy and won't send you borked pistons. Pistons can be damaged in handling, apparently. If you are confident in your measurements then there's your pistons. You could check some of the site vendors (could = should) as they may have something similar on the shelf just waiting for such an occasion, especially if you want to go AAAB, which might be the best bet.

 

Considering all invested in gaskets, hard parts and time spent, saving a couple hundred re-using pistons . . . I'm trying to get my head around this.

[StkmltS]

Are you really planning on re-using those pistons? That is an unusual step. There is no skirt coating, unknown ring land wear (maybe you checked that already, but you need a new set of rings to do it) and something else I can't really think of at the moment. You can see I'm not a fan of this part of the plan.

 

There is a set of BBBB fresh pulls on Outfront site right now for $150 which is $50 more than you really need to spend, but they are trustworthy and won't send you borked pistons. Pistons can be damaged in handling, apparently. If you are confident in your measurements then there's your pistons. You could check some of the site vendors (could = should) as they may have something similar on the shelf just waiting for such an occasion, especially if you want to go AAAB, which might be the best bet.

 

Considering all invested in gaskets, hard parts and time spent, saving a couple hundred re-using pistons . . . I'm trying to get my head around this.

 

BBBB pistons won't work because I'm AAAB (as marked). For the sake putting the motor back together this decade I'm moving forward based on the block's markings, not my measurements.

 

Here's something that should inspire confidence... I don't know how many miles are on the donor pistons, or even if they came from an EJ255 or an EJ257

 

Forgive my ignorance, are stock pistons coated on the skirts?

[xt2005bonbon]

Not answering your question but I recall that EJ255 pistons do not look the same as EJ257. I need to ask Google to verify this claim..

[StkmltS]

This answers that question.

After they're clean it should be easy to tell if they'll suit my needs.

 

If they won't work I'm only out a few dollars. I'll carve out some material and turn them drink coasters.

Nothing says "I know more about cars than you do" more than piston coasters.

Edited July 12, 2016 by StkmltS

[xt2005bonbon]

Yeah. that's the thread I saw a few years back.

[birkhoff]

Oh, the other pistons are used too. I see.

 

I had a link ready to point you to some pictures of new pistons, but I see you are already beyond that. Post 4 in the link you shared; there is a good shot of the skirts. Don't they look nice?

 

If I recall, that long thread went back and forth about whether there really was a difference or not. What I know is, I've never seen a set of the double dot pistons for sale, or in a motor, so apparently we are all using the EJ257 pistons anyway, and that is what you can find lots of these days

[StkmltS]

Oh, the other pistons are used too. I see.

 

I had a link ready to point you to some pictures of new pistons, but I see you are already beyond that. Post 4 in the link you shared; there is a good shot of the skirts. Don't they look nice?

 

If I recall, that long thread went back and forth about whether there really was a difference or not. What I know is, I've never seen a set of the double dot pistons for sale, or in a motor, so apparently we are all using the EJ257 pistons anyway, and that is what you can find lots of these days

New pistons are purdy.

 

If anything about my new used pistons gives me the "uh oh" feeling I'll set them aside and go back to my original plan of using new OEM pistons. I don't like buying things I don't need, but I've saved a decent amount of money elsewhere so my budget won't be affected. Or effected. I dunno.

[StkmltS]

Regarding engine bearings, do we know if Subaru uses different sizes like they do pistons, or do all OEM blocks come from the factory with the same STD size bearings?

 

What happens if I measure the crank/rod journals and my numbers are strange like they were for the cylinders? Should I just buy STD size bearings and use plastigage to verify they are what I want?

[birkhoff]

STD/undersize bearings are designed with the same size shell back. Use undersize if your crank journal is down just a bit. STD and 0.025 mm undersize are available from some suppliers (ACL in particular)

 

Oversize bearings are (almost) unobtainable for our engines. You only use that if you have honed the mainline to correct something. Which means machine shop. Which means, not related to this thread. I'm told king can supply 0.025 OS.

 

There are some marks on the top of the block; 22222 for example. My understanding is that those tell you the factory shell thicknesses on the 5 bores in order, used to fine tune the oil clearance. I've never had this confirmed by the 'experts' so if someone knows. . . It is pretty common to see 22222. If you have a block that says 22122 then maybe something different was fit for bore #3. You could mic the shell thickness to confirm.

 

Here is how it worked out on my block. Measured all the bores and took the smallest diameter on each. Subtracted twice the bearing thickness (you can find this information on the manufacturers website). Add 0.0005 for bearing crush in aluminum. That is your estimated final bore diameter, minimum. Subtract your measured crank journal max diameter and that gives estimated running clearance.

 

I had zero luck using plastigage at such small dimensions, and with all parts out of round.

 

Once you fit the bearings you can do a final bore gauge check on the inside of the shells to confirm everything worked out. It will put light scratches on the bearings. You can polish that out with a piece of newspaper if it bothers you. If something ends up too big, you can swap out for a thicker shell. It is unlikely anything will be too small.

 

Finally, it is a good idea to do one final test fit with plastigage just to check your math. As long as it shows approximate clearance, you are good to go. If you repeat with plastigage, you will get different approximate numbers. That's the problem with plastigage. Final assembly with lube, new washers and torque to spec.

 

Except for pistons, there's your new short block!

 

EDIT: Since I built my block over a year ago, I thought I better check my notes. It looks like the crush allowance (aluminum) should be more like 0.001 (10 tenths) not 5 tenths as reported above. If you have a machinist friend, they might be able to give you a more reliable estimate to work from. This was a one-time thing for me.

Edited July 13, 2016 by birkhoff
corrected crush estimate

[StkmltS]

What's this "bearing crush in aluminum" you speak of?

 

My block is marked 22222, so hopefully you're right and they're all the same STD size. That would make things much simpler. It makes sense that they'd mark the block using the same reasoning as marking it for the bores.

 

The rods are off the crank, ultrasonic cleaned, and 'soaking' in the cool inside today.

The crank journals look good with zero scoring, or at least nothing visible. It's also inside today and will get inspected tonight with the rods.

 

Here are the measurements of my pistons:

P1 - 3.9171, 3.9176, 3.9180, 3.9180 (ave 3.9177)

P2 - 3.9173, 3.9171, 3.9176, 3.9178 (ave 3.9175)

P3 - 3.9172, 3.9177, 3.9179, 3.9179 (ave 3.9177)

P4 - 3.9171, 3.9174, 3.9177, 3.9175 (ave 3.9174)

 

My mic has a resolution of 0.0001" and I'm confident with these measurements. I may throw out my first measurement for each piston (outliers) because I was just getting the feel for the mic. I'm going to check the pistons again tonight and average everything together to get final dims. So far my measurements of the pistons still don't quite match up with the block's AAAB markings.

 

I'll get some fun pics tonight so this thread isn't totally lacking in the visual entertainment department.

[BarManBean]

Have you been using simple green pro (purple) for cleaning, or the normal green stuff?

 

I was told previously that the green stuff can do funky stuff to aluminum.

[StkmltS]

Just the normal stuff.

Looks like I should avoid it moving forward. I've had the timer set at 480 sec (8 min) for all of the ultrasonic cleaning I've been doing.

 

From their website

"When used with caution and according to the instructions, Simple Green All-Purpose Cleaner has been safely and successfully used to clean aluminum. Simple Green All-Purpose Cleaner, Crystal Simple Green Industrial Cleaner & Degreaser, and Simple Green Pressure Washer Concentrates have been used on aircraft, automotive, industrial and consumer aluminum items for over 20 years. However, caution and common sense must be used: aluminum is a soft metal that easily corrodes with unprotected exposure to water. The aqueous-base and alkalinity of Simple Green All-Purpose Cleaner can accelerate the corrosion process. Therefore, contact times for unprotected or unpainted aluminum surfaces should be kept as brief as the job will allow - never for more than 10 minutes. Large cleaning jobs should be conducted in smaller-area stages to achieve lower contact time. Rinsing after cleaning should always be extremely thorough - paying special attention to flush out cracks and crevices to remove all Simple Green product residues. Unfinished, uncoated or unpainted aluminum cleaned with Simple Green products should receive some sort of protectant after cleaning to prevent oxidation.

 

Simple Green has also developed break-through water based cleaners that are safe for use on metals, plastics, rubber and high tech alloys. Extreme Simple Green Aircraft & Precision Cleaner, Pro Series Simple Green Automotive Cleaner, and Simple Green Pro HD are available on both the industrial and retail markets, respectively. These products were initially developed for the aircraft industry and extensive testing shows that they are safe and effective on a variety of metals and other sensitive surfaces even in the most extreme circumstances.

 

Simple Green Stainless Steel One Step Cleaner & Polish is another option for cleaning polished aluminum. This product is designed for light duty metal cleaning and polishing."

Edited July 13, 2016 by StkmltS

[birkhoff]

What's this "bearing crush in aluminum" you speak of?

 

It's, like, what keeps your bearings from spinning around, eh?

 

The outer diameter of in insert bearing is always larger than the bore in the block. The extra is the 'crush'.

 

In an iron block, with iron caps, hot rod magazines will tell you that the crush works entirely to reduce the diameter of the running bore. Machinists will tell you otherwise, that in fact the bearing pushes out against the block and cap enough to slightly enlarge the base bore. How much? Experience.

 

I just reviewed my notes from the build and I was getting a full 0.001 enlargement in aluminum. I'll edit my previous post. So where it says 'add 0.0005' it should say, add 0.001. That was my experience anyway. The effect on the rods (steel) will be much less. Just torque 'em up and measure the running diameter. Swap shells as required.

 

Here are the measurements of my pistons:

P1 - 3.9171, 3.9176, 3.9180, 3.9180 (ave 3.9177)

P2 - 3.9173, 3.9171, 3.9176, 3.9178 (ave 3.9175)

P3 - 3.9172, 3.9177, 3.9179, 3.9179 (ave 3.9177)

P4 - 3.9171, 3.9174, 3.9177, 3.9175 (ave 3.9174)

 

That's quite a range. To be clear, you are reporting four consecutive measurements at the grade point? Perp to the piston pins?

 

In making this measurement, as you sneak the mic onto the piston, move it back and forth a bit to find the diameter, and then up and down to find square. It is a little wiggling exercise that, as you say, you get more consistent with as you practice. Your mic has a friction thimble, right? Use it.

 

Personally I would trust the lower numbers more than the upper ones. If you mic something and get xxx, than you can generally conclude diameter is <= xxx. Unless you are measuring way off the diameter, cranking down too much on the mic or misreading the barrel.

 

It kinda looks like you have a set of 4 B pistons, which can't be right.

[StkmltS]

Bearing crush... got it.

 

I appreciate you asking these kinds of questions. It's helping me rethink my way through everything twice (or more).

 

I did take the measurements from the grade point (approx. 1.50" from the piston face) perpendicular to the piston pin direction. My mic does have a friction thimble and I used it.

 

It's a little tricky getting the mic in the right spot on the OD, which is why I mentioned tossing out my first measurement for each piston (3.9171, 3.9173, 3.9172, and 3.9171). I measured P1 once, P2 once, P3 once, P4 once, then P1 a second time, P3 a second time... you get the idea.

 

I was very observant of where the mic was positioned to make sure I was measuring at opposite points on the OD, not slightly off-center. Even though the flats on the mic do allow a little room for error. Each recorded measurement took two or three tries to get the mic seated to where I thought it felt correct. Precision measuring is very much a touchy-feely game. It's not like using a tape measure. There's a definite "feel" for it that you develop over time.

 

It kinda looks like you have a set of 4 B pistons, which can't be right.

 

But it does somewhat match my measurements of the cylinders.

Edited July 13, 2016 by StkmltS

[birkhoff]

Interesting.

 

Is your mic warming up? Check it against your gauge blocks. You have a 3 inch one, right? Intuition would suggest that your measurements should drift lower if you are expanding the body of the mic with heat, but maybe it distorts the `G' shape and closes up the anvils. Who knows. Thats a lot of error to attribute to temp drift, however. A couple tenths I would believe.

 

FWIW, I find getting the mic on diameter to be pretty easy; as you nicely put it, you can see when the contact point is centred on the moving anvil. It is a little trickier making sure you are right in the other direction. One way is to do a few test points and look for the minimum measurement. With practice, you can actually feel when it is right. That's why I described it as a two step centring process.

[StkmltS]

Rebuilders take your mark... get set... go.

 

http://uploads.tapatalk-cdn.com/20160714/4b3c49eb42093aa64d6a60f0d82322bd.jpg