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Old 01-12-2018, 12:36 PM   #26
Scooby Newbie
Member#: 480485
Join Date: Jan 2018

Bumping this thread to get opinion's on a line boring question.

New here, relatively new to subaru as well.

Picked up a salvage car for a project, stripped down an EJ25 and took it into the machine shop I have used before for a motor build to have it cleaned and inspected. I am being told that the line bore is out of spec by 0.001" on main 5 closest to the flywheel.

I've spent the last couple days looking into information on this and this thread is about the most helpful thing I've come across.

Do I really need to spend the money on a linebore for 0.001, I am not building a race engine. I get if it was 0,005 out like mentioned above it needs to be fixed. Couldn't I run larger oil clearance ACL bearings and crank would never know journal 5 was 0.001 out? Do I even need to do that?

The machine shop was going to send it to another shop, there head quarters to have a second look at it before doing any work but I would appreciate any response with first hand experience.
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Old 01-13-2018, 03:13 PM   #27
Scooby Guru
Member#: 56203
Join Date: Feb 2004
Chapter/Region: Tri-State
Location: south nj
00 RSTI Coupe
Twin Scroll 2.5XTR EJ207


You could run thicker oil, +1 bearings or another bandaid to get it close to spec but it’s not the best way to go about it. What are the actual main clearances as of now?

Keep in mind you can get new blocks for about 1500$ so when you factor that in, the machine work usually doesn’t make financial sense for a DD.
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Old 01-13-2018, 04:17 PM   #28
Scooby Specialist
Member#: 239335
Join Date: Feb 2010
Chapter/Region: W. Canada
Location: Edmonton, Alberta
2011 WRX


Either run the tighter main bearings or get a new block. I would run the tighter mains.
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Old 01-15-2018, 10:37 PM   #29
FuJi K
Scooby Guru
Member#: 3687
Join Date: Jan 2001
Chapter/Region: MWSOC
Location: St. Paul, MN
MY99 GF4 JDM 6spd
NF Performance


You gotta ask them how it is out of round. 3 to 9 o'clock, or 6 - 12 o'clock.
Heat from rod bearing failure will warp the mains.
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Old 01-18-2018, 09:36 AM   #30
Scooby Newbie
Member#: 376219
Join Date: Dec 2013
Location: southern Virginia
1977 5.4L MGB


Unless that machine shop has extensive experience with Subaru's, you are better off taking it elsewhere. The rear main seldom gives a problem, more than likely what they are measuring is a result of 2 possible scenarios. A bent rear dowel or the dowel is just too loose fitting in the driver side case half. You can't just torque the empty halves together and expect them to line up perfectly, because of the loose fit of the dowels.
The proper way is to barely hand tighten the case bolts, measure with a dial bore gage at the parting surface and tap one half in the direction it needs to go to align the halves. At this point, then the mainline can be measured accurately. When the crank and bearings are installed in one half, they pretty much align the second half when it gets mated up.
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