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Old 05-12-2004, 11:03 PM   #1
DoodieHead
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Default Keep throwing rod bearings... HELP!!

Hey guys. I keep throwing rod bearings and dont know why. I think it may be something to do with clearances. I have had this nicely machined crank for the past year and never really gotten around to using it until this last August. Not even a day after the installation of my turbo motor, two rod bearings went out. I just decided to stay with the stock motor until I could get it fixed and started to get piston slap after a few thousand miles. Put the turbo motor back in around January and threw another rod bearing. To keep a long story short I have thrown about 5 rod bearings in the past 5 months, which has entitled me to removing the motor time and time again. My car sits again without a motor and I am in need of some advice before reconstructing, thinking the problem is starvation.

I have read up on the internet that if you have oil pressure your oil pump is working. From what I understand it works when it work and doesnt when it doesnt. So I have eliminated the oil pump. I checked the oil pickup for cracks and there is nothing (no debris on the screen). I bought a brand new WRX pan this last go round just to make sure it was sealed and it was, so that is also eliminated. I even bought an oil cooler because I thought the oil was thinning out way too much, and that didnt even seem to help. There is no oil in my coolant or vise versa. There are no oil leaks under the car at all. ??? Anyone have any ideas, I am at a loss and would appreciate a PRO to troubleshooting this one.

One other thing that I have noticed is that my oil pressure is much lower than it was before I went forced induction (75lbs at 2500RPM stock motor and 45lbs at 2500RPM with turbo motor).

I have come down to scrapping my machined crank and going back to stock one with STD bearings. I believe I have tried everything else to get the oil pressure back up and nothing has worked.

I really hope someone else has had this issue and resolved it (but I doubt it)

Thanks guys,
M|key
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Old 05-13-2004, 12:27 AM   #2
no-coast-punk
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Default

It sounds like you are:

a) using bearings that are too large. If you have excessive bearing clearance your oil pressure will drop quite a bit, especially at lower speeds.

Look at the end of your crank, if it's been machined look at the end of it, the machinist (if they are worth anything) will have stamped a few numbers in it that look like

-10
-20

or

-10

That tells you what size bearings you need to run. In the first case I showed you would need to run bearings that were 10 thousandths undersized on your mains and 20 undersized on your rods. The second example means you need to run 10 thousandths undersized across the board.

b) MAKE SURE YOU NEVER EVER get oil on the back side of your bearings. I've seen guys slap engines together and just dunk the bearings in oil before installing in the motor only to wondery why they spin within 100 miles. Make sure you install the bearings totally dry, and then LIGHTLY oil the faces of them before installing the crank.

Go get a thing of plastigage, plastigage is your friend and will tell you if you are running excessive clearance anywhere.
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Old 05-13-2004, 12:56 AM   #3
Aphex
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use a different machine shop?
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Old 05-13-2004, 08:43 AM   #4
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Quote:
Originally posted by Aphex
use a different machine shop?
Ya, whos building the motor?
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Old 05-14-2004, 12:04 AM   #5
no-coast-punk
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Quote:
Originally posted by totoherbs
Ya, whos building the motor?

This definately sounds like shoddy machine shop work or mis-matched bearings, and for a machine shop to not catch the bearing issue is a travesty.
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Old 05-14-2004, 12:19 AM   #6
White 2.5rs
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tragedy?
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Old 05-14-2004, 01:33 AM   #7
Drac9
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No, travesty- look it up.
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Old 05-14-2004, 01:36 AM   #8
White 2.5rs
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An exaggerated or grotesque imitation, such as a parody of a literary work.
A debased or grotesque likeness: a travesty of justice. See Synonyms at caricature.

tr.v. trav·es·tied, trav·es·ty·ing, trav·es·ties
To make a travesty of; parody or ridicule.
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Old 05-14-2004, 01:45 AM   #9
Drac9
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So the shop made a travesty of good machine work.
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Old 05-14-2004, 01:49 AM   #10
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Old 05-14-2004, 09:50 AM   #11
White 2.5rs
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i guess

i just dont like how its used

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Old 05-14-2004, 04:40 PM   #12
no-coast-punk
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Quote:
Originally posted by White 2.5rs
i guess

i just dont like how its used


Mmmm... gramatical arguments. I love how NASIOC guys can appreciate the finer things in life. It's still definately proper usage though.
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Old 05-14-2004, 06:54 PM   #13
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anything up to and including .0025" bearing clearance should be O.K., much tighter than .001" and you will kill the bearing due to lack of oil volume. Remember folks, oil also carries heat out of the wear surface, it's not just for lubrication. My first 2 thoughts regard what kind of oil pressure do you have, and did the person who did the assembly go overboard with the fuji-bond on the crankcase halves? Excessive sealer will run into the oil galleries that feed the main bearings, and the restricted oil flow will not be enough to also lube the rods. Remember that rod bearings lube from the oil that runs through the main bearings first.
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Old 05-15-2004, 02:42 AM   #14
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Quote:
Originally posted by no-coast-punk
Mmmm... gramatical arguments. I love how NASIOC guys can appreciate the finer things in life.
a joke or not?
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Old 05-16-2004, 06:20 PM   #15
worry
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Default

Have you been reusing the oil pump and the crank and the oil cooler after these failures?

The oil pump's pressure relief valve may be jamming up and the consequent drop in oilpressure may be causing trouble. Look for evidence of jamming in the relief valve assembly (abrasions on the plunger etc).

The oil cooler, if you are using one, should probably not be reused after a bearing failure as you cannot be 100% sure to have cleaned all debris from the heat exchanging core.

Debris may also get caught in the oilways of the crank, and it is not possible to clean these oilways thoroughly unless you remove the oilway plugging ball bearings before doing so.

Worry
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Old 05-17-2004, 10:37 PM   #16
DoodieHead
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Default

Man, I totally forgot about putting this post up. I did not know it would get such a good turnout.

As far as the bearings go, they are .50mm undersized as they should be w/ STD mains. I think that maybe having the crank polished and turned has made the journals much smaller than they should be, which is what is causing the bearings to keep throwing out.

I decided to go with my stock crank (which has never seen a bad bearing) and go from there. If I throw a rod bearing with this one, I have no idea what to do.

I am also looking for a dealer for some STD rod and main bearings (other than Subaruparts, as they are very pricey). If anyone could help I would really appreciate it (looking for TOGA or Clevite 77 dealers).

Thanks,
M|key
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Old 05-17-2004, 10:43 PM   #17
yamarocket630
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Call Payn Technologies at 248.694.3966 They can get some very nice aftermarket bearings for half of what the stockers cost.
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Old 05-19-2004, 03:17 PM   #18
jdk
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Default pick-up gasket

.......

Last edited by jdk; 04-18-2006 at 05:44 PM.
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Old 05-19-2004, 07:25 PM   #19
no-coast-punk
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This is why I like to place oil pressure gauges on the turbo feed off the head, since the head is the least likely spot to get oil, it's the most important spot to read oil from. It still sounds like a bearing issue due to your turned crank though.
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