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Old 09-10-2005, 09:05 PM   #1
bugeyes
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Default Modified EJ20/25 cranks for high rpm....

Was reading a thread on the EJ25 forum about crank/rod failures. It seems some guys are modifying oil passages for higher rpm use. This would also be applicable for EJ20's (probably more so as they tend to rev higher).
There is theory that at higher rpm's the crankshaft is unable to supply oil to conrod journals 2 & 3. This is due to the crank centre journal having to supply 2 rod journals instead of just 1 as per rod journals 1 & 4.
Apparently subaru has modified the factory crank in the ver8 sti to overcome this problem and some engine builders are modifying their cranks also.
As I have a crank to be able to have a look myself and a set of bearings, I must say it seems feasible that when the crank main oil passages are in line with the join of the two bearing halves it would create a short period of low oil supply.
I beleive some engine builders are drilling extra passages in the crank journals to supply extra oil at 90' from the orginial holes.
If anyone knows anything more about this or if someone could post some pics of a sti ver8 crank showing oil passages that would be great.

Also on the subject of cranks. My subaru manual states that crank/bearing clearances are to measured by plastigauge to a factory specification clearance of 0.0004-0.0012 thou with a maximum of 0.0016 thou. I was talking to Tony Rigoli's crankshaft grinder which was doing my crank and he told me Tony runs a clearance of 2 to 2.5 thou clearance (which I do now also). I think this is to provide more clearance for higher rpm's use.
Interesting............
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Old 09-10-2005, 10:53 PM   #2
Agkelos
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I know Ron and Axis Motorsports does this, you could contact him to see what exactly he does.
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Old 09-11-2005, 12:30 AM   #3
ejsportcom
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this is pretty interesting, would love to see pics of all the oil passages and what not to get a better idea of flow...
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Old 09-11-2005, 04:56 AM   #4
bugeyes
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Also I've been trying to find a supplier of full grooved mains bearings. These would give full oil supply all the way around the crank journal.
If you dont know the standard bearings have a partial tapered oil groove that can lead to possible oil shortage at high rpm's.

Haven't been able to find one yet. Anyone also know anybody that makes/sells these?
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Old 09-11-2005, 09:35 AM   #5
tmarcel
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bugeyes,

ACL out of Australia who makes bearings for our engines (they don't have them listed on their website though). I am building my 2nd EJ257 engine right now and we found that ACL makes a "race series" bearing for both the cond rods and mains. If you would like the part numbers I can get them for you tomorrow. My bearings and packing slip are sitting at the machine shop right now for fitting. I would also recommened finding a good dry film coating if you have a company near you to do that. I used Calico Coatings to do mine http://www.calicocoatings.com/index.phtml?coatings

Also, just wanted to comment from your first post. It would seem that the extra bearing to journal clearance would have a negative effect on oil psi performance?
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Old 09-11-2005, 11:19 AM   #6
sjl1614
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bugeyes,

I am waiting for my modded crank from axis, then i can take some pics of the extra oil holes
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Old 09-11-2005, 12:10 PM   #7
Crawford Performance
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We have never modified the oiling system on a stock crank in any of the motors we have sold, period.

The stock crank has shown its self to be a little on the weak side, as we have broken many in half. But even those did not have a bearing issue when dismantled ?

We get calls on a weekly basis from our dealers that are ordering a motor to replace a competitors motor that has failed. This call usually comes after multiple attempts at replacing the motor with another that has the same fate.

Engine builders blame the tuner and the tuner blames the engine builder. This scenario will never end, so please do not get cought up in the excuses as they will only cost you money.

Do your homework, that is the best advise I can give you.

Quirt Crawford
www.crawfordperformance.com
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Old 09-11-2005, 07:27 PM   #8
bugeyes
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Crawford Performance, I find your comment about breaking crankshafts interesting, however I do expect you are running extremely high hp engines.
I would think for the majority of owners that run less than 400whp the standard crank strength is sufficient (if not exposed to severe knock or mechanical impact).
What is your opinion on bearing to journal clearance, the oem specifications seem very tight for a high revving engine?
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