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Engine, Exhaust, Transmission Discuss the FR-S | 86 | BRZ engine, exhaust and drivetrain.


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Old 01-05-2025, 03:53 PM   #15
NoHaveMSG
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Plastigauge isn’t perfect but given the OP’s measurements I would have used it to double check myself in that situation. At least one rod or main would have been plenty to verify.
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Old 01-07-2025, 03:56 PM   #16
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My question is has the measuring tool been calibrated/reading correct? I would double check with another tool, yes plastigauge would be a good double check.
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Old 01-08-2025, 02:19 AM   #17
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Main bearing oil clearance measuring out of spec

I measured everything again, using the crank pin journals as baseline instead of the gauge pins and no meaningful difference.

I guess the plan for now is to use the 0.026mm tighter bearings by King Bearings. This conveniently puts my measurements back within the looser end of specifications or just slightly outside of them.

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Originally Posted by Opie View Post
How are you measuring the ID of the bearings without the engine assembled? Using a micrometer on an uninstalled bearing is your problem. They got to be compressed, installed in the journal to get an accurate measurement. Do it right, use plastigauge like everyone else.
With the block assembled and torqued, without a crankshaft. I’m not sure how you would measure a loose bearing as you described.

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Originally Posted by Tokay444 View Post
If he compresses them, there will be even more clearance. Plastigauge is for a amateurs who don’t have the correct measuring equipment.
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Originally Posted by Grady View Post
My question is has the measuring tool been calibrated/reading correct? I would double check with another tool, yes plastigauge would be a good double check.
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Originally Posted by Opie View Post
Incorrect, but thanks for trying. Main & rod bearings are slightly larger than the journal, when bearings are seated in the journal the tension from this holds them in place. Then when you set the crankshaft in place and torque the block halves to the correct value you will get the true clearance. Anything else is just guessing.

It's no wonder there are so many failures on "garage" rebuilds for this engine...I'm still 0 for 150+
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Originally Posted by Tokay444 View Post
lol. “uSe PlAsTiGaGe! yOuR dOiNg It WrOnG”
The guy has actual measurements with high quality direct and indirect precision measuring tools. Why on earth would he use Platigauge? It has its place. That place isn’t here.
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Plastigauge isn’t perfect but given the OP’s measurements I would have used it to double check myself in that situation. At least one rod or main would have been plenty to verify.
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Originally Posted by NoHaveMSG View Post
Plastigauge isn’t perfect but given the OP’s measurements I would have used it to double check myself in that situation. At least one rod or main would have been plenty to verify.
I don’t get my equipment calibrated but, I have an assortment of gages and multiple calipers that overlap gages, and everything measures within 0.002mm. Plastigage measurements have been within 0.005mm of micrometer measurements.



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Originally Posted by Ultramaroon View Post
Do the original bearings show any visible signs of wear? I see the difference between the Toyota and BRZ specs. I'm with Tokay on this. I'll go a step further. Since I first became aware of how much engine speed affects oil temperature, I've quietly assumed that it is a direct result of dumping the same amount of work into a fraction of the oil volume seen in previous generations of journal bearings.

I bet the original bearings were fine,
You are correct. The original bearings measured oversized the same amount as the brand new King bearings and show almost no wear. A few little marks that look like they had some embedded debris at one time, but nothing of concern.




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Originally Posted by Eaton PSI View Post
I had similar issues when assembling my engine.
The ACL race series bearings come in both 0.025 oversize and undersize sets.
I ended up using 1/2 a std set and 1/2 0.025 oversize set to get all clearances good.
Expensive and time consuming getting it all good but it can be done.
Cheaper than machining anything! This is the route I am going, but will be all 0.026 tighter.

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I think the block relaxes after a couple years of heat cycling so they're never quite the same as a new one.
I also had issues with alignment as I removed all the dowels to make it easier to set up on the machine for sleeves. This was a mistake! I ended up having to make offset dowels to get the tunnel to line up true again. A huge amount of work but probably still less than line boring it.
I have all the leftover bearings from my build listed for sale in the australian classifieds section.
Yeah, it does almost seem like the block loosened up, unfortunately I don’t have bearing bore dimensions to verify!

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Originally Posted by Eaton PSI View Post
Another tip for fine tuning clearances.
If the std bearings are to loose and the 0.025 oversize are to tight, you can use one of each shell on a journal which gives you 0.012 clearance increments.
Be very careful if using this trick on main bearings as you may create alignment issues if thick and thin shells end up on opposing sides of the tunnel.
Rod bearings no problem, run the thinner shell in the cap.
Good to know. It looks like I’ll be running all oversized so no worries.
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Old 01-08-2025, 07:11 AM   #18
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There is always the chance that the clearances were all out of spec from new. Maybe subaru is a bit sloppy building them. Maybe that's why they're a bit more prone to failure than other engines.
Oil pressure at idle spec is about 7psi according to toyota, crazy low. With main clearances set at middle of spec, 0W-30 oil and a WRX pump I get 12-15psi at idle.

Who wants to buy a couple of new short blocks, strip, measure and post the data. I'm sure we'd all be very appreciative!
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Old 01-08-2025, 09:04 AM   #19
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Quote:
Originally Posted by mkodama View Post
I don’t get my equipment calibrated but, I have an assortment of gages and multiple calipers that overlap gages, and everything measures within 0.002mm. Plastigage measurements have been within 0.005mm of micrometer measurements.
That is enough double/triple checking to say your measurements are good.
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Old 01-08-2025, 10:59 AM   #20
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Originally Posted by Grady View Post
My question is has the measuring tool been calibrated/reading correct? I would double check with another tool, yes plastigauge would be a good double check.
Whether the micrometer he's using is calibrated or not, it almost irrelevant. He's setting the mic to the crank pin diameter, and zeroing the bore gauge to it. Are suggesting the bore gauge may not be tracking correctly over a <.002" stroke?
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Old 01-08-2025, 12:58 PM   #21
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Quote:
Originally Posted by Eaton PSI View Post
There is always the chance that the clearances were all out of spec from new. Maybe subaru is a bit sloppy building them. Maybe that's why they're a bit more prone to failure than other engines.
Oil pressure at idle spec is about 7psi according to toyota, crazy low. With main clearances set at middle of spec, 0W-30 oil and a WRX pump I get 12-15psi at idle.

Who wants to buy a couple of new short blocks, strip, measure and post the data. I'm sure we'd all be very appreciative!


I was wondering if that main clearance was a cause of failures as well. Extra main clearance, means lower oil pressure for both the rod and main bearings. Then when someone gets rod knock it gets blamed on abuse or neglect.

I wish there was more data on what the main bearing shell bores should be. It seems like a pretty vital piece of info to leave out of the service manual.

Luckily this engine still had 20psi idle oil pressure with 0W-40, and down to maybe 16psi at worst idling immediately getting off the track and 240F oil temps.
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Old 01-08-2025, 01:13 PM   #22
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Originally Posted by mkodama View Post
I wish there was more data on what the main bearing shell bores should be. It seems like a pretty vital piece of info to leave out of the service manual.
Is the table at the end of page EM-115 about taking an *indirect* measurement of this? (I’m asking to check my learning from this thread, so please don’t feel compelled to reply if it’s any trouble.)
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