I pulled this from a post from a friend on EvoM this was done on an Evo 8 crank, it was a very well known shop in Germany that did this test. I provided a crank for this test.
We did grind a crank down all the way to determine the deep of the hardening.
The hardening is not nitrite, its inductive hardening ( thats the reason why you can polish the crank.
It was an used Evo8 crank with an rod bearing failure on cyl.1, which was trash anyway due to the failure
We started to grind the number 2 Rod surface.
ALL dimensions in metric (mm) here. Hardness is not an absolute value in our case, its relative measurement!!
Initial : 47.993mm Fillet depth: 0.49mm Hardness: 88
1st grind : 47.893mm Fillet depth: 0.39mm Hardness: 88
2st grind : 47.743mm Fillet depth: 0.24mm Hardness: 88
3st grind : 47.493mm Fillet depth: none Hardness: 86
4st grind : 47.243mm Fillet depth: none Hardness: 84
5st grind : 46.993mm Fillet depth: none Hardness: 68 hardness drops fast
So , in conclusion, you can grind the Crank Rod pin ( only rod testet ) down.
so, 0.25 mm is possible when the fillets should be there and 0.50 mm if fillet doesnt matter or can be refreshed.
Any more does not make it because fillets gone and also hardening drops ( extreme loss after the -0.75 grind )
Also, the grinding should be done in an really smooth way, so it should not be done like an V8 crank. There should be removed only a small amount of material, with cool down times in between. The hardening can change extreme if to much heat is transfered into the crank. ( tried that at Rod position 3, more material in one grind, hardening changes 5 more point than rod 2 )
But, there is an other problem you will run into.
All Bearing manufacturers doesn't make the right bearings for the turbo application.
The max grind to get Turbo bearings is -0.25mm. smaller to get bearings from them.The bigger OS will be only for the N/A 4g63 / 4G64.
This was approved from King bearings, the materials and coats used will be different than and they do not advise to use in high HP applications.
Same Information from Clevite, ACL and Glyco.
Also, Mitsubishi has different bearings ( but same dimensions ) for the 4g63T and 4g63 n/a Engines.
It may be possible that someone has get Bearings as an custom order, but not "off the shelf".
For my self: For an almost stock Evo ( stock turbo ) i would use an g rinded crank (-0.25) when an new one is not in the price range..
In any high HP application ( 500++) i would never used an grind crank.
Get an new or good used one. Better safe then sorry.
here in Germany, its easier and cheaper to use an new crank all time, because the grinding is expensive. Grinding all 4 rod sections is about 500$.
In the states, i assume, it will be much cheaper because you have more Engine shops then here in Europe.
my 2 cents
We did grind a crank down all the way to determine the deep of the hardening.
The hardening is not nitrite, its inductive hardening ( thats the reason why you can polish the crank.
It was an used Evo8 crank with an rod bearing failure on cyl.1, which was trash anyway due to the failure
We started to grind the number 2 Rod surface.
ALL dimensions in metric (mm) here. Hardness is not an absolute value in our case, its relative measurement!!
Initial : 47.993mm Fillet depth: 0.49mm Hardness: 88
1st grind : 47.893mm Fillet depth: 0.39mm Hardness: 88
2st grind : 47.743mm Fillet depth: 0.24mm Hardness: 88
3st grind : 47.493mm Fillet depth: none Hardness: 86
4st grind : 47.243mm Fillet depth: none Hardness: 84
5st grind : 46.993mm Fillet depth: none Hardness: 68 hardness drops fast
So , in conclusion, you can grind the Crank Rod pin ( only rod testet ) down.
so, 0.25 mm is possible when the fillets should be there and 0.50 mm if fillet doesnt matter or can be refreshed.
Any more does not make it because fillets gone and also hardening drops ( extreme loss after the -0.75 grind )
Also, the grinding should be done in an really smooth way, so it should not be done like an V8 crank. There should be removed only a small amount of material, with cool down times in between. The hardening can change extreme if to much heat is transfered into the crank. ( tried that at Rod position 3, more material in one grind, hardening changes 5 more point than rod 2 )
But, there is an other problem you will run into.
All Bearing manufacturers doesn't make the right bearings for the turbo application.
The max grind to get Turbo bearings is -0.25mm. smaller to get bearings from them.The bigger OS will be only for the N/A 4g63 / 4G64.
This was approved from King bearings, the materials and coats used will be different than and they do not advise to use in high HP applications.
Same Information from Clevite, ACL and Glyco.
Also, Mitsubishi has different bearings ( but same dimensions ) for the 4g63T and 4g63 n/a Engines.
It may be possible that someone has get Bearings as an custom order, but not "off the shelf".
For my self: For an almost stock Evo ( stock turbo ) i would use an g rinded crank (-0.25) when an new one is not in the price range..
In any high HP application ( 500++) i would never used an grind crank.
Get an new or good used one. Better safe then sorry.
here in Germany, its easier and cheaper to use an new crank all time, because the grinding is expensive. Grinding all 4 rod sections is about 500$.
In the states, i assume, it will be much cheaper because you have more Engine shops then here in Europe.
my 2 cents
