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Old 09-08-2010, 03:32 PM   #1
WRXt4cy
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11 STi BW 8374 E85
02 v8 Spec C E85

Default Bearing sizing help

I am in the process of rebuilding an EJ257. I have measured all the rod and main pins on the crank and everything measures within the standard size for oil clearance purposes.

The block is stamped 22221 and according to the FSM this indicates that the #1 journal is different that 2-5. The old bearings reflect this in that #1's bearing is noticeably larger (and measures thicker) than 2-5.

I've searched all over and read the FSM but cannot come up with any good information on how to figure out the proper bearings to get. The block stamp seems to have possible values of 1, 2 or 3 for each journal, 2 being most common, 1 showing up from time to time and 3 being the rarest to see. It would seem that 1 indicates an oversized journal, so does 2 mean standard and 3 mean undersized?

The FSM talks about undersized bearings in terms of oil clearance for the crank and main pins, but it doesn't talk about under/oversized bearings to fit the journals properly.

There are markings on the crankshaft as well - does this indicate anything useful?

What about getting bearings to fit the rods? Can there be a need for over/undersided bearings to fit over/undersided rods?

I don't understand how to figure out what size rod and main bearings I need to get for my block/crank/rod combination.

Can anyone help?

Thanks in advance.
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Old 09-08-2010, 08:02 PM   #2
soobaviator
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08 Audi Q7 4.2 PRM

Default

If you have a stock or new crank OEM clearance range on the mains is going to work best. The middle of that range should work well. larger than that and you may need other measures done, possibly a 12 mm pump. You did the first thing correct which is to measure the journals. You want to keep the bearing clearances as follows:

1 and 5 equal
2 and 4 equal but slightly larger than 1 and 5
3 largest clearance of all

Rod bearing clearances should be uniform.

If you are using a new crank and new bearings there most likely won't be an issue. Clearance on the rods is recommended on the high side of OEM .001-.0014.

The FSM is not gonig to tell you what earings to get for a performance motor. And you won't know the exact clearance until you put the bearings in and measure. Best bet is to chose standard size for the mains and +.001 for the rods and go from there. Worst case is that you may need to align hone or polish the rod journals to get the best clearances.



-soobaviator
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Old 09-08-2010, 10:25 PM   #3
WRXt4cy
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Thanks soobaviator - that info is helpful.

The build is basically a budget build for a friend to get his STi back on the road after cracked ringlands on 2 & 4. The block was usable but needed new sleeves and had to be bored 20 over. Its getting forged pistons but its probably never going to see anything beyond stage 2, at least not for a quite a while.

He is tapped out money-wise after the machine work on the block, cleaned and surface plained heads and 4 new valves. He has a little money left for bearings, an oil cooler and other small odds and ends but none left for additional machine work. I want to build it as best I can but I really need to get the right bearings the first time around.

Its my understanding that you can only get bearings in specific sizes; I don't understand how to get them "a little bigger" or "a little smaller".

Given my measurements and the block stamp, what would I need to tell the parts guy at the local Subaru dealership in order to get the right bearings for this build?
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Old 09-09-2010, 12:20 AM   #4
soobaviator
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Getting aftermarket bearings is cheaper than OEM and there are more options. I would look at getting ACL std mains and Race rod bearings. The package should be less than $100. There are no options in the OEM bearings except for undersize and unless you grind the journals you have no need for them.

If not doing any machine work there is really no way to tweak the clearances. You will have to accept what you get. However the ACL combination I mentioned should work fine. If your friend on OEM then that is not going to be a disaster either but a little more clearance on the rods is better for longevity. In any case for OEM bearings you need the standard size sets for rods and mains.

The standard STI pump should be fine with the combo, just make sure that oil pressure is checked during the run-in.

How many sleeves put in? That's pretty bad damage then. It may have been cheaper to find a used EJ255/257 block tear it down and go from there. Good luck with it in any case.
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Old 09-09-2010, 01:55 AM   #5
WRXt4cy
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Default

Thanks again.

I think we'll look at the ACL route.

What about the fact that the #1 journal seems to be larger than my other journals? Do I need to account for this when ordering ACL main bearings?

I am going to check the oil clearance with plastigauge and if anything is far outside the specs, I am going to tell him I won't build it with getting it machined.

In hindsight he wishes he would have just gone with new case halves and thats what I would have done if it were mine, but the machine work is already done.

It got new sleeves on both 2 & 4 due to slight cracking. Only the sleeves themselves had damage to them.
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Old 09-09-2010, 10:16 AM   #6
soobaviator
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08 Audi Q7 4.2 PRM

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There is no way to account for it the bearings are one size range and that's it. It's not going to be an issue as the crank already worked fine in with the original standard size bearings, it's going to be fine with another set.

In point of fact #1 and # 5 journals should be biggest of all, #2 and #4 should be smaller and #3 should be the smallest measurement. It's the way subaru manufactures the crank to balance the oil delivery.

Rather than plastigauge I would check clearances by measuring the journals, as you already have and then using a bore gauge on the assembled case halves and connecting rods. If no access to bore gauges snap gauges will work. Plasti would be the least desireable of the three methods for best accuracy
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Old 09-10-2010, 10:09 AM   #7
WRXt4cy
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11 STi BW 8374 E85
02 v8 Spec C E85

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soobaviator - thanks for all your help. I sent you a PM to get a little more info from you, please check that if you don't mind. Thanks.
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