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Old 08-16-2007, 02:45 AM   #1
reddevil
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Default Crank walk, lets talk.

First off..


What causes it in Subaru motors?

How long can you run with it?

What are the side effects?



I ask this because of a few reasons....

I hate to eat crow, and so therefore try not to be 100% correct EVER. But in a recent NASIOC conversation, I was saying that a .010-.017 crankwalk will not kill a newly built motor. And I still believe this. But I admit that crankwalk is BAD. But how bad and for how long?

And again, another reason I post this is that I built a motor last November with NO crank walk, ran it maybe 1500-2000 miles, torn it down tonight, and guess what? Crank walk, about .010... Tore the block down and the center thruset bearing was worn on both sides to expose the brass. The oil itself was "clean" looking, but the oil attached to the pan was very "shiny". Yeah, lots of the main thrust bearing. This motor was pushing alot of power, but not that long....

So, post up your thoughts....
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Old 08-16-2007, 12:53 PM   #2
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Need to edit what I said about the center thrust bearing I said was worn.

It wasnt. I specced it against a brand new one, and the brand new one already has exsposed brass sides, and I used the micromometer and they were withen .002 of each other, and the factory "grind" was still evident.

I will check the crank then and see if that was the problem....
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Old 08-16-2007, 01:05 PM   #3
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how tight are you making your accessory belts
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Old 08-16-2007, 01:38 PM   #4
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IIRC, I was talking to someone about crankwalk in DSM's, and they claimed it was caused by the clutch actuation... specifically on very heavy push-type clutches.

You're saying center thrust bearing, so I am assuming that is a phase 1 block... and WAY back in the day, I thought I had heard one of the reasons they went away from center thrust bearings was because of the crankwalk issues those motors had.
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Old 08-16-2007, 01:48 PM   #5
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Quote:
Originally Posted by 8Complex View Post
IIRC, I was talking to someone about crankwalk in DSM's, and they claimed it was caused by the clutch actuation... specifically on very heavy push-type clutches.

It ocurred predominately in the 7-bolt motors. Over revving and harsh clutch acuation were a few of the big causes.
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Old 08-16-2007, 01:52 PM   #6
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I have to say that it is caused from clutch,not only on subaru motors but others as well.When I recieve used JDM motors I always check this (to see if I want to accept the motor or not)none of the motors that came from automatics had any excess play but quite a few of the manual trans ones had quite the slop.SUMI
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Old 08-16-2007, 02:24 PM   #7
reddevil
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So I was talking to the machine shop guy, and he says there SHOULD be about .005 to .008 walk in the crank, how else will oil get in there? I didnt actually measure the one I just tore down unfortunately, so maybe it was within spec?

As for pressure plate pressure causing wear? I have yet to have someone explain how this can happen. The pressure plate presses against the Flywheel. There is NO pressure against the bearing due to the pressure plate.
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Old 08-16-2007, 03:18 PM   #8
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Quote:
Originally Posted by reddevil View Post
The pressure plate presses against the Flywheel. There is NO pressure against the bearing due to the pressure plate.
These two statements seem contradictory to me.

Pressing against the flywheel would exert a force on the bearing... no?
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Old 08-16-2007, 03:43 PM   #9
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Subaru engines do not have an issue with crank walk.
The thrust bearing cener or rear is a 360 degree deisgn.

Now talking about a high milage engine, bearings and thrust surfaces do wear.
But this is normal on engines well above 100,000 miles.

Really stiff pressure plates can cause pre-mature bearing failure and thrust surface wear.

- J.
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Old 08-16-2007, 03:44 PM   #10
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It irritates me when people who know better use "crank walk" for "excessive crankshaft thrust clearance" or "crankshaft end float", both of which are the proper terms. It's ALMOST as irritating as "pillow ball" for "spherical bearing" which is the worst.

I was hoping the term would die with the DSM cars, but I was wrong.

Almost always caused by heavy clutches, no matter what engine, BTW, or sometimes badly adjusted clutch linkages.

What clutches were behind the engines you're having trouble with?
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Old 08-16-2007, 03:47 PM   #11
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Quote:
Originally Posted by x99percent View Post
These two statements seem contradictory to me.

Pressing against the flywheel would exert a force on the bearing... no?

Yes, you're right.

The crankshaft thrust bearing absorbs all of the clutch release forces.

Perhaps he's confusing the forces that release the clutch from the clamping load on the clutch plate. The second is exerted against the flywheel and pressure plate bolts, not the crankshaft thrust bearing.
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Old 08-16-2007, 04:21 PM   #12
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Well, I didnt know better about the terms.
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Old 08-16-2007, 05:04 PM   #13
Jeremy@Cobb
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Default

All is equal in my book, I build numerous engines daily (different terminology doesn't bother me).
Excessive thrust bearing clearance
Crankwalk (excessive clearance can allow the crank to physically walk forward and backwards in the block).

With an aggressive pressure plate (stiff pressure plate) the force from pushing the clutch pedal in and out which pulls the clutches sprung "fingers" which engages and disengages the clutch disc.
This movement can actually force the crankshaft against the thrust bearing causing premature failure.

Reddevil- your terminology is fine I understood without a second guess.

- J.
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Old 08-16-2007, 05:42 PM   #14
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I am running a dual diaphram pressure plate rated at 550 torque. Its STIFF.

But the wagon will only see maybe 500-1000 miles a year.
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Old 08-16-2007, 06:50 PM   #15
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Quote:
Originally Posted by 8Complex View Post
IIRC, I was talking to someone about crankwalk in DSM's, and they claimed it was caused by the clutch actuation... specifically on very heavy push-type clutches.

You're saying center thrust bearing, so I am assuming that is a phase 1 block... and WAY back in the day, I thought I had heard one of the reasons they went away from center thrust bearings was because of the crankwalk issues those motors had.
this is an old subaru conversation.
EA81s were walkers to the point of detrimental to themself, the cam surfaces at any angle other than perpendicular acted like a jackhammer. No getting away from it. the ea82 is a genious. The ej is grabbing at signals it shouldn't be, and that is indeed another walker maker, rod breaker (as proven frequently- it is the tranny killer as well- no "middle signal", and I don't want to explain it).
All my ea82s howl a turbo sound from the middle with equal length plug wires... hovering in the realm they should have been, it is called perfection.
play in the middle bearing is fantastic, push it to the limit, increase the oil pump if need be. No regrets and all gains for cylinders as well. common sense. it may even increase flow on stock oil pump making pressure look low- all while it is better in many ways to read low.

reddevil is a nut with the ej! love reading the threads of your ups and downs, and sc adventures.
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Old 08-17-2007, 08:09 PM   #16
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the amount of force applied to the pressure plate to open it, is the exact same force that is applied to the thrust bearing. think about it, that force has to go somewhere, it just doesnt disappear when the clutch fingers open. the only thing resisting that effort is the thrust bearing. and yes, i read that same article/thread, thats why all suby motors are now made with rear-end (#5) crank thrust bearings, and because at high rpms( think 8-9k) the crank would wobble on the crank bearings and destroy them. but again, thats just from what i've read.

~Josh~
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Old 08-17-2007, 08:16 PM   #17
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Quote:
Originally Posted by bgd73 View Post
this is an old subaru conversation.
EA81s were walkers to the point of detrimental to themself, the cam surfaces at any angle other than perpendicular acted like a jackhammer. No getting away from it. the ea82 is a genious. The ej is grabbing at signals it shouldn't be, and that is indeed another walker maker, rod breaker (as proven frequently- it is the tranny killer as well- no "middle signal", and I don't want to explain it).
All my ea82s howl a turbo sound from the middle with equal length plug wires... hovering in the realm they should have been, it is called perfection.
play in the middle bearing is fantastic, push it to the limit, increase the oil pump if need be. No regrets and all gains for cylinders as well. common sense. it may even increase flow on stock oil pump making pressure look low- all while it is better in many ways to read low.

reddevil is a nut with the ej! love reading the threads of your ups and downs, and sc adventures.
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Old 08-17-2007, 08:20 PM   #18
reddevil
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Quote:
Originally Posted by ballitch View Post
the amount of force applied to the pressure plate to open it, is the exact same force that is applied to the thrust bearing. think about it, that force has to go somewhere, it just doesnt disappear when the clutch fingers open. the only thing resisting that effort is the thrust bearing. and yes, i read that same article/thread, thats why all suby motors are now made with rear-end (#5) crank thrust bearings, and because at high rpms( think 8-9k) the crank would wobble on the crank bearings and destroy them. but again, thats just from what i've read.

~Josh~
There is an answer finally that EXPLAINS stuff! Good stuff.
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Old 08-17-2007, 09:15 PM   #19
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Default Wobble ?

It's been known forever that heavy pressured pressure plates eat thrust bearings thats a fact of life. A multidisk clutch can run less pressure if it has more surface area. (motorcycles) Also there use to be pressure plates that had a centrifugal action to apply more pressure without as much spring pressure. Subies have more drivetrain to drive and lots of traction. When the hp goes up the clutch pressure will need to be increased. Building a bad ass motor means building the rest to keep up, shop for the lowest pressure clutch that will survive till teardown. Maybe we need to research the thrust bearings and their alloys. Hopefully race quality means better. Also if you start with all the clearances at the optimum it might help.I went to look at some thrust bearings I have from stock motors I've taken apart to look at. I have a ej20 na that has really been abused and the thrust looks only worn on one side but it's quite a bit wider than the phase 1 motors I had to compare to. I looked at a phase 1 2.5 dohc na that has 170k miles on it and put the shell on the crank and it barely took a .003 feeler guage. I don't know but this might have been an auto. I didn't get the flywheel with it. Maybe we need to make all high performance phase 1 motors rear thrust to get a bigger thrust surface.

Charlie
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Old 08-17-2007, 10:11 PM   #20
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now iam scared , i got this exedy multidisc clutch on my young hybrid ...
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Old 08-18-2007, 12:57 AM   #21
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So then will running a twin-disc clutch put less stress on the crank thrust bearing then say a hyper-single?
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Old 08-18-2007, 11:28 AM   #22
charliew
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Default pressure on the clutch

Come on guys, whatever the pressure is that it takes to depress the clutch is just like pressing on the rear of the crank with that same pressure. Thats been stated better than me above. That pressure is applied to the thrust bearing. The thrust bearing is the only thing that stops the crank from moving forward, use the lightest pressure pressure plate you can get by with and the best clutch disk that you can afford. Take one half of the block with excessive end play with the two rods and pistons installed and apply the release pressure of the clutch to the back of the crank and see where it gets tight, rods, and pistons. Also I would imagine that when the crank end play gets excessive then the rod journals start becoming the thrust bearing and then the side pressure is applied to the wrist pin and from there to the sides of the piston. Well I'm not sure if it would really go that far, but you get the idea. A phase 1 motor with two thrust bearings might be neat if set up right to allow for the thermal expansion of the block. Maybe a simple coating on the pressure side. Also the best oil with the most slippery additives will make a big difference. Race motors have been dealing with this forever. There are solutions that are acceptable.
Charlie

Last edited by charliew; 08-20-2007 at 12:17 AM.
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Old 08-18-2007, 11:06 PM   #23
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Quote:
Originally Posted by bgd73 View Post
this is an old subaru conversation.
EA81s were walkers to the point of detrimental to themself, the cam surfaces at any angle other than perpendicular acted like a jackhammer. No getting away from it. the ea82 is a genious. The ej is grabbing at signals it shouldn't be, and that is indeed another walker maker, rod breaker (as proven frequently- it is the tranny killer as well- no "middle signal", and I don't want to explain it).
All my ea82s howl a turbo sound from the middle with equal length plug wires... hovering in the realm they should have been, it is called perfection.
play in the middle bearing is fantastic, push it to the limit, increase the oil pump if need be. No regrets and all gains for cylinders as well. common sense. it may even increase flow on stock oil pump making pressure look low- all while it is better in many ways to read low.

reddevil is a nut with the ej! love reading the threads of your ups and downs, and sc adventures.

Dude, seriously... Get help.
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