Bought an sti3 recently with a shafted engine (big ends).
Having it rebuilt at the moment, just to standard spec.
Every engine I have ever had rebuilt, has had the a crank regrind, not a new one.
Never had a problem.
My question is, what is so different about the impreza crank?
How people on here have had their crank re-ground and still have a healthy engine?

Thanks in advance.
Chris

 

BTTT

 

for how much a new crank costs it would in my eyes be good VFM to know there wasnt a weak point, considering how much rebuilds cost.

IMO of course

 

IIRC the surface hardening on the cranks is only very shallow, so if a regrind is done there is quite a high possability that it will expose a softer metal.

Gary.

 

Have to admit I don't know the exact nature of the hardening process on Subaru cranks but if it is one of the low temperature treatments such as Nitriding or Tuftriding, the crank is ground to size then heat treated. As it's a low temp treatment there is no distortion and the journals are just polished to finish. The surface is very hard but also very shallow, hence furter grinding may well remove the hard skin.
JohnD

 

John D is pretty much spot on.

see also my posts on the end of this thread, and Zen performance / APIdavid posts as well.

Don't regrind your crank.

https://www.scoobynet.com/general-te...hlight=nitride

 

bttt

 

Chris. I've personally heard two engine builders (both subaru specialists) say that you must NEVER re-grind an Impreza crank- they did exaplin it, but I went into mechanical ludite mode. I believe it's due to the explanation given above though; certainly rings bells! They also claimed that given the relatively low cost of a replacement; it's just not worth farting around with: bin it!

Ns04

 

There are a number of reasons not to regrind, besides the surface hardness, which is less of an issue with good forged cranks than people think. Getting the abrasive dust out of the oil ways isn't always guaranteed, nor is the resulting straightness of the crank. The biggest issue is that I've only come accross one or two machine shops that will grind the subaru crank properly. The narrow journals make it difficult to get in with some grinding machines, and i've seen a few botched jobs.

Just buy a new one.

Paul

 

just out of intrest how much was the rebuild m8??..might need one myself soon?

 

Around £1900 inc a new crank.

 

That was by the guy near the station??

I thought it was just a shop.

 

They have a workshop aswell with a ramp round the back.
Speak to craig or paul.