Andrew's DiySB Rebuild

[StkmltS]

http://uploads.tapatalk-cdn.com/20160714/50233f2669bc1abd2248a847582d42dd.jpg

 

Bearings for #1 (top) and #2.

Cap halves are above the rod halves, except #2 where I put the rod half on top (woops).

http://uploads.tapatalk-cdn.com/20160714/7bac328226fbcc5248b9cc5b07c92fbf.jpg

 

Bearings for #3 (top) and #4.

Cap halves are above the rod halves.

http://uploads.tapatalk-cdn.com/20160714/d9d13cdc9b2109abc0162600a77981dc.jpg

Edited July 14, 2016 by StkmltS

[StkmltS]

Crank journals measured, pistons re-measured, bearings removed from rods, and rod caps torqued down to 39 ft/lbs. I'll post numbers for the crank and pistons tomorrow.

 

The case halves, rods, and measuring equipment are back in the holding chamber (unused bathroom shower) patiently waiting to be measured tomorrow night.

[birkhoff]

There is no spec in the FSM for the base bore in the rods. You can only check for oval. Same as the main bores in the block.

 

How long before you have your new bearing shells in hand?

[StkmltS]

There is no spec in the FSM for the base bore in the rods. You can only check for oval. Same as the main bores in the block.

 

How long before you have your new bearing shells in hand?

 

Actually there is, for the rods at least. The table on the top right of page ME(H4DOTC)-80 specifies 2.0466" to 2.0472" as the standard diameter. The same diameter is specified again in the table on page -82.

 

I was like "what the heck is a crank pin?" After a little googly-googly I found a wikipedia page brilliantly titled "Crankpin" that has a pretty self-explanatory illustration.

 

**edit** actually there isn't, those numbers are for the rod journals on the crank.

 

I'm not ordering bearings until after I measure the case main bores tonight. My track record for measuring ID's is pretty questionable so far and I'll probably end up buying STD bearings, but I want the data first. Even if the data isn't perfect. It may be risky buying STD bearings that don't perfectly match my numbers, but at least it'll be a known risk instead of just a shot in the dark. There's also the chance that I'll get good numbers for the case main bores and I'll be able to confidently know I need STD sizes. The same goes with the rod bearings.

Edited July 14, 2016 by StkmltS

[StkmltS]

Whoa... I accidentally ventured into the H6 section of the FSM and it's weird.

[birkhoff]

Correct on your edit. One might think you could work back from those numbers and the known bearing thickness and oil clearance, but you still won't know the base bore because the designed crush is an unknown.

 

What you can do is measure the big end bore parallel to the parting line and assume that that is the designed base bore since rods elongate mostly in the other direction. Now measure the other direction for oval.

 

You probably know this already, but base bores are supposed to be perfectly round. Running bores are not -- the shells taper out near the parting line. Not much, but enough to measure. That slight opening up is for the oil wedge. That is why you always measure running clearance perp to the parting line of an insert bearing.

[birkhoff]

All this measuring and discussion of errors got me curious.

 

I have a few new and used pistons here after tidying up. Two brand new A-grade pistons measure 3.9178 at the grade point. Both of them, and the measurement is repeatable. Then I grabbed one of the used A-grade pistons from the 180K motor I just pulled and tore down. 3.9175 at the grade point. Skirt wear was not too bad; I can see the machine marks on almost all of the skirt, except for a couple of polished areas just above the grade point.

 

There are some pictures of these pistons in my rebuild thread. Impossible to know how much diameter was lost since there can be variation in the A-grades when new (I guess) but that gives you a sense of the scale of things.

 

Tolerance on machined parts for these motors seems to be very high. Cranks, pistons, rods etc. I assume tolerance on the case bores is very high too, but then everything distorts once the case is out of the clamps. FWIW, I think you should aim for more consistent measurements on machined parts. You have made great progress and just a little more practice will get you there.

 

One more point. The measurements I made above were at some temp, somewhere below 20C since that is ambient daytime temp up here these days anyway but my basement is quite a bit cooler. I didn't take any special care with handling the mic, but I worked fairly quickly. It took me a couple of tries to get back into the rhythm mind you. It's all about practice and feel.

[StkmltS]

Pistons

After much thought these are the numbers I'm going with for my pistons.

 

#1 - 3.9178"

#2 - 3.9175"

#3 - 3.9177"

#4 - 3.9176"

 

The diameters don't match up with they should be based on the bore sizes stamped on my block, but other than having my gauges re-calibrated and remeasuring everything this is the best I can do for now.

 

Crankshaft

Main journal #5: Cylindricity and out-of-roundness are both 0.0003", putting them 0.0001" over the allowed limit of 0.0002".

Rod journal #4: Out-of-roundness is 0.0003", putting it 0.0002" over the allowed limit of 0.0001".

 

Overall I'm very pleased with the numbers I took away from my crank.

We're talking about one and two tenths of a thousandth of an inch here. We use CMMs here at work that aren't repeatable to four decimal places (although they claim to be). My measurements could easily change by one or two tenths based on many different things, so I'm giving my crank a passing grade and moving it along to the next round. Franky I'm amazed at how pretty the journals look and how well I did measuring them.

 

Bonus points: I didn't look up what the the diameters are supposed to be until after I was finished, so my measurements weren't influenced at all by what I wanted them to be. It shouldn't be uncomfortable measuring something without knowing what it's supposed to be, but it is.

[StkmltS]

Also, I'm glad you guys convinced me to buy new torque wrenches. Last night putting the rod caps back on with my new TW was a pleasure compared to using my Harbor Freight wrench.

[birkhoff]

From my build records, crankshaft journal ovals (#1 - #5, in tenths) were

 

1, 2, 2, 0, 0

 

Smallest min diameter was 2.3619 on #4 which exactly hits min spec. Largest max diameter was 2.3622.

 

These measurements were taken after the crank had been cleaned and polished at the machine shop.

 

On assembly, calculated main oil clearance was (#1 - #5, in tenths)

 

12, 13, 14, 16, 14

 

Minimum stock is 12, but that is the best I could do even with mixed shells.

 

Crankpins were all below minimum. Again, I used mixed shells to get oil clearance back into the stock range.

 

You seem to be finding much the same so plan on two sets of shells to make things right. No big deal in the grand scheme.

Edited July 14, 2016 by birkhoff

[StkmltS]

Tonight's plan:

Dinner, swimming with the fam, swap cars with father/father-in-law, put kids to bed, kiss wife goodnight, car time.

 

Torque SB halves together

Measure main bores

Measure rod bores

[xt2005bonbon]

Try not to think about the SB while you have "Dinner, swimming with the fam, swap cars with father/father-in-law, put kids to bed, kiss wife goodnight"

[StkmltS]

Try not to think about the SB while you have "Dinner, swimming with the fam, swap cars with father/father-in-law, put kids to bed, kiss wife goodnight"

Good advice.

I didn't do anything to the motor last night. My wife had other things that needed taken care of, if you know what I mean

Translation: I begged and she gave in

 

My wife + kids will be at my wife's sister's house today and most of tomorrow, so I have plenty of uninterrupted time for car stuff this weekend.

 

My wife and her twin sister have this thing for spontaneously putting together yard sales. They get it in their heads and it has to happen asap. I'm talking pronto! No ad in the paper, nothing online, no signs until the night before... just a bunch of stuff neatly presented in front of the house. If we had good stuff to sell I'd be all for it, but this will be the third yard sale in two summers and at this point we have no good junk left. This weekend I'm predicting they'll bring in less than $80 (combined). Anyways, I love my wife and I'm glad she has a twin to do this kinda stuff with.

[heiche]

wonder how much you could get for some used bearing shells?

[StkmltS]

wonder how much you could get for some used bearing shells?

 

I never imagined there would be a market for used bearings. I'll have to poke around and see.

If they're worth reusing to someone else... should I consider reusing them?

 

When the motors finished I'm going to round everything up and see if there's anything worth trying to sell. If someone wants to offer something between then and now I'd certainly entertain all offers, naturally.

[heiche]

not sure what yard sale items you will have left to offer

 

definitely replace bearing shells and rings at a minimum, but the sky is the limit.

[StkmltS]

not sure what yard sale items you will have left to offer

 

definitely replace bearing shells and rings at a minimum, but the sky is the limit.

 

Ahhh that's what you meant

 

So I'm rethinking my side-track decision to only replace #2 with another used piston. I've gone this far, new pistons are relatively cheap, and there's money in the budget for them.

 

My measurements of the bores don't exactly make sense dimensionally, but I'm confident that my cylinder-to-cylinder readings are accurate (cyl 1 is largest, cyl 2 is second-largest, cyl 4 is third largest, and cyl 3 is smallest.) I can't make sense of it why I measured cyl 3 smallest vs cyl 4 per the block markings. I want to trust Subaru's factory markings as more correct than my measurements, but I can't let go of it in my head.

 

I'd like opinions.

If I buy new pistons should I go with AAAB per the block markings, or should I "double-hone" the B cylinder (#4) and go with four A pistons?

Or even just hone the cylinders equally and go with a combo of my measurements and Subaru's markings and use four As.

Edited July 15, 2016 by StkmltS

[heiche]

New pistons sounds like a good idea. Not sure what to suggest on the "create an AAAA motor" question though.

 

Just confirming - your block is AAAB? So your block is marked with AA on the passenger side (cyls 1 / 3), and AB on the driver side (cyls 2 / 4).

[StkmltS]

Top is driver side.

The bronze crack looking thing is a piece of a wire brush I exploded by running it backwards.

 

http://uploads.tapatalk-cdn.com/20160715/83c975b669f5e1963198184c9330aeb4.jpg

[birkhoff]

 

So I'm rethinking my side-track decision to only replace #2 with another used piston. I've gone this far, new pistons are relatively cheap, and there's money in the budget for them.

 

This ^^^^^^^ makes my day!

 

Ask the forum for a set of AAAB and ye shall receive.

 

Don't try to change any bore size unless you are getting a professional hone. Even then, I would be wary of not getting a round bore back unless the shop has a torque plate. Bottle brush hone? Forget it.

[SBT]

Torque plate is the only way to do it right.

[StkmltS]

I got a little carried away after I decided to clean up a "few" castings marks. My air compressor is still crying from the abuse.

Edited July 18, 2016 by StkmltS
Loaded pics to site server for posterity

[xt2005bonbon]

It's crazy to see how small these blocks are.

[SBT]

It is amazing when you see the whole engine together, just how low and compact they really are.

[Tehnation]

i still think they are pretty big... most 4 cylinders have 1 cylinder head. it being flat just makes it look like its small i think.