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Old 07-18-2016, 04:10 PM   #1
Advanost
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Default Engine builders, I need some advice!

Greetings Nasioc,
My name is Aaron and I've been a long time forum lurker but rarely post. I have owned my WRX for nearly 2 years and I am preparing to build my first Subaru short block. I am not a complete novice, and I have done a lot of research on Subaru specific builds, but I'd like some further advice.

The build will consist of a 2006 EJ255 "702" series short block that has spun a rod bearing. The plan is as follows:

New OEM hardened crank

New King main and rod bearings

STI rods. I am hoping to reuse 3 of the rods and just replace the 4th, but that will depend on how the big ends looks and where they spec out at.

Mahle PowerPak (4032 alloy) pistons. Will probably run 99.75mm but depends on how the cylinder walls clean up. The block has been sitting in a garage and the bores are rusted up.

I will be using Fowler micrometers and bore gauge to measure all clearances.

Aiming for .0015" mains and .002" rods. Piston to wall will be set at .0025"

I am willing to deck the case halves and align bore the mains if they're too far out of spec. I will gap the rings according to manuf. spec.

What are some other things I need to consider? Am I missing something critical? I have a factory service manual so I can follow all the proper torqueing procedures. Thanks for the help!
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Last edited by Advanost; 07-18-2016 at 04:43 PM.
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Old 07-18-2016, 05:12 PM   #2
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To add some clarity:
The cylinders will be bored with the case halves torqued together, torque plate installed on the bores, and cylinder head torqued to the opposite side. Gaskets will be used. The mains will also be checked and align honed (if needed) in the same manner, assuming the machines will accept the size of the block.
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Old 07-18-2016, 07:13 PM   #3
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Make sure whoever is doing the align hone knows what they are doing. It's not an easy job on a subaru block.
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Old 07-18-2016, 07:24 PM   #4
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Quote:
Originally Posted by monkeyposeur View Post
Make sure whoever is doing the align hone knows what they are doing. It's not an easy job on a subaru block.
Thanks, I'll be sure to check with the machinist to see if he is familiar and comfortable with Subaru blocks.
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Old 07-19-2016, 12:21 AM   #5
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If you are wanting a line bore, the cost of that plus boring/honing of cylinders isn't cost effective when you can buy a new set of halves for around $900. Just my $.02. Other than that, your target specs are great.
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Old 07-19-2016, 01:40 AM   #6
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Quote:
Originally Posted by Juice66 View Post
If you are wanting a line bore, the cost of that plus boring/honing of cylinders isn't cost effective when you can buy a new set of halves for around $900. Just my $.02. Other than that, your target specs are great.
Thanks for your input. From the way I understand it (Team Scream or some of the other popular machinist/builders may correct me) Subaru mains aren't the best even on new case halves. I think either Motion Machine, Team Scream or ASF said they pretty much line hone every new EJ25 block to get proper specs. I'm not necessarily concerned with cost as much as getting the job done right the first time. If I still have to machine the mains on a new block, I'd rather pick up a junk block for a lot cheaper, rebuild the mains and get exact PTW clearance instead of trying to "drop in" pistons.

My ultimate concern is missing something important and causing the block to fail prematurely. I'd actually like to become a respected engine builder, and this first block will be a fantastic learning experience. I want to soak up as much knowledge as I can before I proceed into this.
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Old 07-19-2016, 06:27 PM   #7
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Quote:
Originally Posted by Juice66 View Post
If you are wanting a line bore, the cost of that plus boring/honing of cylinders isn't cost effective when you can buy a new set of halves for around $900. Just my $.02. Other than that, your target specs are great.
He can get all that work done for under 900 and could easily get the specs he wants. I'd go that route before a new block.




OP: who is doing the machining? MM?
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Old 07-19-2016, 06:47 PM   #8
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Quote:
Originally Posted by Paul View Post
He can get all that work done for under 900 and could easily get the specs he wants. I'd go that route before a new block.




OP: who is doing the machining? MM?
I haven't settled on a particular machinist. I'd like to find a local guy and save shipping costs, but I'm afraid they won't be very competent with Subaru blocks. I will personally have access to a nice machine shop (free of charge) in about a month which I can use at my leisure, but I've never done machine work so I don't trust myself to do it right.
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Old 07-19-2016, 07:08 PM   #9
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you'll have a hard time finding a good machinist let alone one that does line bores.
MM and ASF are the only shops I know that do line bore on the regular.

MM is probably closest shop and probably one of the best so I'd go that route if he can fit you in. His prices seem very fair to me also
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Old 07-19-2016, 07:11 PM   #10
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I suck at geography..LOL IDK why but I thought he was closer than 10+hrs away
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Old 07-19-2016, 07:31 PM   #11
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Quote:
Originally Posted by Paul View Post
I suck at geography..LOL IDK why but I thought he was closer than 10+hrs away
Yeah, there aren't a lot of well-known Subie machine shops in my neck of the woods. I'll be moving to about an hour outside of Atlanta in a few weeks so I may have better luck with a shop there. I know Topspeed is a known shop, so I may call them up and see who they recommend for machine work.
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Old 07-19-2016, 08:21 PM   #12
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like I said very few shops will do a line bore.....Line hone you can find but I wouldn't bother. Now if you just want bore/hone there is more options, just my 2cents
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Old 07-19-2016, 09:37 PM   #13
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Agreed, no point in line honing, it's only padding your bill. Line bore every block. As stated before, even from the factory the mains are crappy.

Last edited by KillerBMotorsport; 07-20-2016 at 11:06 AM.
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Old 07-19-2016, 10:03 PM   #14
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Did you mean "no point in line honing"?
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Old 07-19-2016, 10:17 PM   #15
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Quote:
Originally Posted by KillerBMotorsport View Post
Agreed, no point in line boring, it's only padding your bill. Line bore every block. As stated before, even from the factory the mains are crappy.
Quote:
Originally Posted by niemkij View Post
Did you mean "no point in line honing"?
Yea, I think Chris means no line honing. I think I've seen him state that line honing our mains doesn't do a great job of getting them into spec.

Last edited by Advanost; 07-19-2016 at 10:25 PM.
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Old 07-19-2016, 10:28 PM   #16
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I was thinking it was a typo also
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Old 07-19-2016, 10:41 PM   #17
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Quote:
Originally Posted by Paul View Post
I was thinking it was a typo also
Hopefully he'll chime back in and clarify. I have heard that the #1 main is usually pretty tight on new EJs, sometimes less than .001". Although we don't normally spin main bearings, I'd like to make sure ALL my clearances are right on target. Anyone have suggestions for an oil pump? I think the EJ255 has the 10mm pump (single AVCS) but I've read some engines with looser main/rod bearings don't have the best hot-idle oil pressure with the 10mm. Should I step up to an 11mm or just thoroughly clean and reuse my 10?

Another note: what other clearances should I spec? Thrust bearing? We don't have issues with "crank walk" like DSMs but I haven't found any information on it either.
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Old 07-20-2016, 10:18 AM   #18
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I can almost guarantee it was since I know KB had a block line bored and the crank spun very freely by hand. KB is also a big advocate about using the pump that came on your car, check oil pressure and maybe add shims if needed.

Do a search for MM posts he has posted a lot of good info. I made a thread in this forum awhile ago when I measured my mains and he added some good information in there. He's very nice and always answered my questions so maybe shoot him a email/pm

For clearences on the thrust Id assume the factory ones are good. There was a thread in this section with IAG specs and we know those motors hold some major power so maybe take a look at them.
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Old 07-20-2016, 11:10 AM   #19
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Argh... Edited for typo

I'd run a new 10mm pump. I don't recommend reusing pumps with any mileage on them. Why use a pump with wear (even if it's only 20% into your service wear limits) when you're assembling a fresh engine
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Old 07-20-2016, 11:28 AM   #20
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fwiw, I only replaced one of my sti rods when i put them in my ej22 block and used CR4125XPG STD rod bearings. Plastigauge put me at .0018 finals but it took some moving around to get all my rods consistent. trying to get .0020 on all rods with one set of bearings and a new untouched crank will be next to impossible. I tried weighing the rods to go with the pistons for balance but the pistons were to the bores and to get the bearing clearences i had to move the rods too. So i chose oil clearance over a couple grams of balance. Another reason to have block assembled at a shop, they might be able to trade out your rods for other rods and will likely have extra bearings laying around to get you all the sepcs you want without all the extra machine work

Last edited by no694terry; 07-20-2016 at 11:33 AM.
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Old 07-20-2016, 12:42 PM   #21
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Quote:
Originally Posted by KillerBMotorsport View Post
Argh... Edited for typo

I'd run a new 10mm pump. I don't recommend reusing pumps with any mileage on them. Why use a pump with wear (even if it's only 20% into your service wear limits) when you're assembling a fresh engine
Sorry I worded that weird I ment use the same size pump that came in your car not the old one. Always go new the 150$ is worth piece of mind
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Old 07-20-2016, 01:20 PM   #22
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Quote:
Originally Posted by no694terry View Post
fwiw, I only replaced one of my sti rods when i put them in my ej22 block and used CR4125XPG STD rod bearings. Plastigauge put me at .0018 finals but it took some moving around to get all my rods consistent. trying to get .0020 on all rods with one set of bearings and a new untouched crank will be next to impossible. I tried weighing the rods to go with the pistons for balance but the pistons were to the bores and to get the bearing clearences i had to move the rods too. So i chose oil clearance over a couple grams of balance. Another reason to have block assembled at a shop, they might be able to trade out your rods for other rods and will likely have extra bearings laying around to get you all the sepcs you want without all the extra machine work
Thanks for your input! I'd like to do the assembly myself because I know how much effort and care I will put into it (more than anyone else). It's also more cost effective to do the labor rather than outsource it. I don't mind buying several different sized bearing sets, but I was hoping to spec the mains and rods with the old bearings to get an idea of clearance, then buy whatever size I needed to get my clearances proper.

What would you guys recommend if I'm having a hard time getting the mains to spec out properly? I know I'll need to line bore, but do you guys have any suggestions beyond that? I've read of some half-shell heroes using over/under sized bearings on half the block to get the proper clearance. What about micro polishing the crank? Or very lightly sanding (perpendicular to the journal) the backs of the shells? I think that would affect bearing crush though.
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Old 07-20-2016, 02:43 PM   #23
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I always love the piece of mind comments, get a new oil pump, get a new oil pan, get new piston rings, get new gaskets, get new clutch, get new motor mounts, get new timing kit, all this piece of minds add up to thousands quickly when all you need is a zanax and a competent eye to inspect used parts.
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Old 07-20-2016, 05:36 PM   #24
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If you get a line bore and a new crank getting the clearences should be pretty easy Id think. Maybe just get 2 boxes of bearings std and OS and it should be pretty easy. Honestly just talk to MM he'll give you all the answers you need and you know they'll be right
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Old 07-22-2016, 05:26 PM   #25
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I'll ask and see what he suggests. I was speculating that clearances may vary a little with minor differences in bearing shell thickness. I could always shuffle them around the block until I get everything to work out. If I wanted to balance the engine myself, where should I remove material from the rod and piston? I'll get a nice digital scale so I can balance each rod and piston individually.
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