Check my main and rod clearances.. what will work?

[Leggercy_mang]

Hey guys, been lurking a while, now I’m knee deep in an ej255 rebuild and have some interesting crank journal measurements that I need someone more knowledgeable than myself in Subaru to take a look at.

To me it looks like the mains will be fine with the 0.025 oversized bearings. The rod bearings however look to be a bit small. Even with the 0.025s I’m still 0.040 on 2 and 4 and 0.020 from standard size on 1 and 3. Next oversized step up with ACL is 0.25 which is way overkill.

 

Since I can’t upload my photo for some reason here’s what I have:

Rods: 1-51.943 2-51.9176 3-51.943 4-51.9176

 

Mains: 1-59.9694 2-59.944 3-59.944 4-59.944 5-59.944 (Thrust)

 

My question is, am I thinking about this wrong or backwards or something? The Crank is in nice shape, only 128k on it and polished up very nicely.

 

What’s your opinions LGT?

[Darth SpecB]

Well it's hard to say, considering we don't know the inner diameter of the blocks journals. Ofcourse the readings will not be consistent since your using a crank with miles on it. I would recommend torqing the block to spec to take into account bearing "crush" since it is an aluminum block. Then take those measurements and minus the crank journal measurements. As long as your within spec it should be fine. I believe it's. 0004-.0012 for the mains and .015 for the rods. I'd have to double check the manual. Keep in mind some people purposely run bigger tolerances with thicker oil, so if you know what your doing you can get away with it. If you have time take a look at my build thread in the ICU section. All of the measurements start at about post #50 or so. A lot of things in those threads you can learn from our mistakes. Good luck!

 

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[Max Capacity]

This is not something you want to mess up. Find a good local machine shop and have them check your measurements. Well worth the few bucks it will cost.

[Leggercy_mang]

I appreciate it guys Thanks!

[Darth SpecB]

Let's assume your measurements are accurate. If you are getting .04mm oil clearance on 2 and 4, this is within spec. (.017-.045mm) however you are getting .02mm on 1 and 3, this tells me 2 and 4 were polished a bit more than the other 2 journals. Both of these clearances are well within spec and the motor will run, so I'm not exactly sure what your question is. As long as you torqued the block to spec with bearings in place your clearances should coincide with your measurements. Yes you have .02mm more clearance on 2 journals but you are running a "polished" crank. If this is something you don't want to worry about, you can spend 300$ for a new STI heat treated crank and run standard sized bearings. But if it were me, I'd just run with what you have.

 

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[Leggercy_mang]

And that’s what I’m going to do, just run with what I have. After a bit more reading and better understanding, I’ve ordered a standard set of ACL race mains and rod bearings. Going to install, hit them with some plastigage and assess. The spec you state is the first I’ve seen that though,, where I was coming from was adjusting the sizes I have to the standard bearing size “min/max shaft size” using oversized bearings. I’m pretty sure that was the wrong way to look at this. I appreciate the help!