IW STi Forum banner

1 - 20 of 49 Posts

·
Premium Member
Joined
·
137 Posts
Discussion Starter #1
I've never built an engine before but I'm fairly technically inclined. I work in the precision machining industry and know a fair bit about measuring, tolerances, blueprints, and generally good mechanical practices. I also used to work on aircraft in the Air Force. So I have fairly good knowledge of how technicians should perform work.

I'm considering building an EJ25 from scratch. I'd like to start with a bare block and just work at my own pace. Are there any obvious markings I should look for or look to avoid when choosing a block? I know the difference between an open and a closed deck. Wondering if there was some nuance that I should keep in mind.

I'm sure I'll have additional questions as I go and I'll try to keep in all in this thread.

Thanks
 

·
Registered
Joined
·
935 Posts
awesome idea. if you like putting stuff together, building an engine is one of the most rewarding...ableit frustrating and stressful, things you can do on a car. Once you do this, everything else in cars feels easy. (Maybe minus rebuilding a transmission. )

Few things you need to check for.

1. Check the decking on the block. Without a feeler gauge, its hard to see if its warped. but you dont want any pitting or gouges. I bought a set of case halves a few years back and didn't inspect them. When I got them, there was a deep gouge in the deck and I was pissed. Seller told me they were solid, but luckily I went back to that place and got my money back.

2. Inspect main journals. When you spin a bearing, bearing material gets deposited everywhere. Cranks are forged steel which is much harder than aluminum. This can cause the crank to "push" the bearing material into the journals. which is no bueno. I like to use the "fingernail test". I will drag my fingernail across the journals, and if anything catches, its not a block I want.

3. Inspect sleeves for damage. this one is usually easy to spot but unless you are sleeving a block, you dont want any damage to the cylinder walls. Fingernail test is good for this too.

4. Check head bolt holes for damage/pulling threads. I've seen instances where someone has their entire block put together and is putting their head bolts in. They overtorque, for whatever reason, and pull the threads. This is a PITA to deal with. Get a used headbolt, and just lightly thread it in each hole. This can be repaired with timeserts. if you plan on going 1/2 or 14mm head studs, dont worry about this. they have to be rethreaded anyway.

5. Check all other bolt holes for damage. I just got a "refurbished" EJ253 for a forester and the water jacket bolt hole and PS Pulley mounting holes were badly damaged. I was able to tap them, but I was not happy about it. Another good one is checking timing mounting holes. those are easy to strip/damage.

Thats all I can think of off the top of my head. Make sure to get a FSM for your year, which I have if you need, that will help this process tremendously.

I am in the process of building a closed deck EJ257 for fun but have 26k miles on my home built block.
 

·
Registered
Joined
·
105 Posts
One that I can think of off the top of my head is the cylinder size markings on top of the block. Standard bore is 99.5mm on an EJ25.

Some blocks have A's and some of them have B's. They refer to the cylinders inner diameter in the position the letters are in on that side of the case half. IIRC, an 'A' cylinder has a slightly larger ID than a 'B' cylinder. You'll want to determine which cylinders are A and which are B to help you select the correct piston.

To find this marking, you'll want to look at the top of the block, straight down behind the alternator. You'll see the crack where the case halves meet, and on one side of the crack, you'll see two letters, either AA, BB, AB, or BA, and same on the other side of the crack. The letter closest to the front represents the cylinder closest to the front and vise-versa, and will help you determine if you have the larger or smaller cylinder.

A sized = 99.505-99.515 mm
B sized = 99.495-99.505 mm

As a side note, some people consider this difference to be minute enough to not worry, but others choose to go that extra mile, considering some companies list an A piston and a B piston.

Sent from my SM-G955W using Tapatalk
 

·
Premium Member
Joined
·
5,202 Posts
A shop that does a great rebuid will line bore the crank journal and deck block and heads.
They'll bore the cylinders and not tolerate different sized pistons.

They'll use new new stock crank, new bearings everywhere, and new pistons, and probably new rods, (though stock rods aren't bad) and balance the rotating assy.

I would not hesitate to build my own engine, but I'd want a shop that has all the right machines and fixtures to machine it. I trust IAG in this regard and I'd just buy a short block from them with all the above included.frse

They rebuilt my block exactly as above in 2015 as one of the first ones they did in house - prior to them having a real pre-built offering. Now you can just go online, click and wait a couple of weeks . . .

Added:when I think of a project car I jump to not stock. If you are never going to mod, then all that is unnecessary. Pretty much what Leemanfor wrote, except I'd definitely bore and use new pistons.

Blown up STIs: have you seen it's oil?
 

·
Premium Member
Joined
·
137 Posts
Discussion Starter #5
I don't have lofty goals for this engine build. I'm testing myself more than anything else and seeing where the bumps are.

I will likely purchase the case halves from ebay if I can't source them locally that I can examine. I'm not going to pay more that $500 for them. I'll be sure to look through the return policy well if I go to ebay. I don't have a set of bolts to check the threads. So I'll likely have to rely on a visual inspection of the threads.

With regards to machining of the block, it was my intention to have the deck and journals machined if the rest of the block is copacetic. I also plan to have the heads machined as well once I source a good set of those.

What method of measurement do you employ with a feeler gage for checking for case half warping? My though was that you'd use an indicator and run it over the surface.

Also, I do have the FSM. I reads a lot like AF technical data so I like using those whenever possible.
 

·
Registered
Joined
·
279 Posts
personally i use a straight edge and light to see if theres any warping...light is a lot thinner than a feeler guage ;), you can also get a long bolt with same thread pitch, if its a used block definitely check for runout...bore taper scratches etc. a good machine shop will usually take care of a lot of that...also get pistons based on their size recommendation to get the PTW clearance and they will be labelled for which piston goes where, wife told me i am no longer allowed to build my blocks due to time down and the frustration level lol
 

·
Premium Member
Joined
·
137 Posts
Discussion Starter #7
Thanks for the tips. I'll probably bide my time and wait for a block to come up for sale locally. I definitely don't want to look the horse in the mouth before pulling the trigger. Perhaps my local tuner knows of some good case halves available.
 

·
Registered
Joined
·
935 Posts
personally i use a straight edge and light to see if theres any warping...light is a lot thinner than a feeler guage ;), you can also get a long bolt with same thread pitch, if its a used block definitely check for runout...bore taper scratches etc. a good machine shop will usually take care of a lot of that...also get pistons based on their size recommendation to get the PTW clearance and they will be labelled for which piston goes where, wife told me i am no longer allowed to build my blocks due to time down and the frustration level lol
mine is getting the same way when I build stuff. shes like "can't you just order an engine?"
 

·
Registered
Joined
·
105 Posts
LOL, Does she have a hobby she'd rather build-it-herself rather than just buy pre-made product?

Don't mean to brag, but my wife definitely doesn't have this issue. She's working on my junk along with me.
 

·
Registered
Joined
·
935 Posts
haha nah. For her, its the end goal. she just wants to see the end product

for me, its the process. Of course the end goal is important but its awesome to say I've literally done all of the work on my car, including the engine. (well minus tuning)
 

·
Registered
Joined
·
105 Posts
Haha, fair enough.

The hands on experience is nice. Although, since now this is my daily (it wasn't at the time I built my forged block), I'd opt for IAG block if mine went again. ~19,000 miles and going strong, so hopefully that doesn't happen.

Sent from my SM-G955W using Tapatalk
 

·
Premium Member
Joined
·
137 Posts
Discussion Starter #13
Thankfully. My STI is no longer my daily and I don't drive it from Oct thru March/April. I live in the rust belt and the salt here eats cars. They salt trucks should be painted like hungry, hungry hippos. I want to leave my stock block alone and just have fun getting to know the platform and its' workings. I have a new shop to work in that has lots of space.
 

·
Registered
Joined
·
935 Posts
you can also join your local Subaru Buy pages on facebook.

I scored a blown EJ257 for $150.

it had forged pistons and rods in it.

I sold the pistons for $200 and basically got a set of free case halves.
 

·
Super Moderator
Joined
·
10,687 Posts
Good luck on the build, before I did my first one I watched over a dozen YouTube videos. My second build went 10.74 at 121 at Indianapolis Raceway part in a 2004 STi after Corbin Johnson tuned it. I was happy about that result. I named the shortblock Rhonda.
 

·
Premium Member
Joined
·
5,202 Posts
I want to leave my stock block alone and just have fun getting to know the platform and its' workings. I have a new shop to work in that has lots of space.
That explains a lot.

Still I'd never put the effort into building a stock power level block - and you already have one!
 

·
Premium Member
Joined
·
137 Posts
Discussion Starter #18
Not sure what that explains... But okay.

I want to go through and learn more about matching bearings to the crankshaft and when I get to the heads, learn how to port and polish them myself. I will go with upgraded internals and valve train components. I just have to do it at the pace that Fatherhood and professional life will allow.
 

·
Premium Member
Joined
·
5,202 Posts
Having a running car and a shop explains the timeline. Youll have a new block by the time you need it - when nearing 200k :) ?

(mine was rebuilt at 185k. It would have made 200k even if I hadn't.)

You wrote no lofty expectations, now your saying aftermarket internals - not that thst means lofty . . . no judgement, Im just trying to understand as if we were having a conversation.

I havent built an engine in many years due to career, fitness, kids, and lack of shop. Now kids are grown, have a shop, fitness is less an issue (long story short bad ankle) and I am considering that my next car could start as a project . . .
 

·
Premium Member
Joined
·
137 Posts
Discussion Starter #20
Okay... So after some contemplating. I'm considering purchasing an OEM shortblock instead of searching for components. This way, I can have some piece of mind that I'm starting with a good parts.

I'd still like to disassemble the SB in order to learn about it and perhaps some mild modification. But for the cost and piece of mind, it might be the way to go.

Also, I wont' have the possibility of warping/machining cost and have the parts cleaned.
 
1 - 20 of 49 Posts
Top