pros and cons when running oversized(.25mm) bearings and grinding cranks on 500hp+ motors

I ve always looked at it as long as machine work is done properly and motor is assembled correctly there should be no issues if it was making 500hp or 100hp, am i worng? i had a customer look at me crazy today when i mentioned running a oversized bearing in 450hp car ,I 'm just looking for some info from diffrent engine builders.....

 

if you have to grind the crank for some reason and use oversized bearings i dont see a problem..

edit: forgot about the nitrited crank..nevermind


Modified by mmuller at 9:59 PM 4/16/2005

 

The stock crank is nitrated at the factory.Nitrating is a surface hardening treatment that doesn't penetrate very deep and will be compromised by grinding.With the supply of good used cranks available I personally would not grind a Honda crank.
Glenn

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by NJIN BUILDR &raquo;</TD></TR><TR><TD CLASS="quote">The stock crank is nitrated at the factory.Nitrating is a surface hardening treatment that doesn't penetrate very deep and will be compromised by grinding.With the supply of good used cranks available I personally would not grind a Honda crank.
Glenn</TD></TR></TABLE>

but in my eyes thats wasted money, casue u can(well i can) get a crank re nitrated, for the cost of 40-65 rather then buying a another crank, this is what i have always done...

v8 guys have been doing this for yrs and making tons more power...

 

keep going I wana know more about this , and also what about if you were looking for 600hp

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Big Will &raquo;</TD></TR><TR><TD CLASS="quote">

but in my eyes thats wasted money, casue u can(well i can) get a crank re nitrated, for the cost of 40-65 rather then buying a another crank, this is what i have always done...

v8 guys have been doing this for yrs and making tons more power...</TD></TR></TABLE>

I guess I don't see the wasted money.Lets say $50 for the nitrate,and $80 for the regrind(which would be cheap for a quality grind around here) and your at $130.Now your limited in bearing sizing.My experience with nitrating is its hard to control material growth.Its typical practice to leave the crank on the big side before nitriding and finish grind after.Twist and distortion is also common from nitrating.Bearing clearance is not as critical in domestic v8's mostly because your not dealing with aluminum blocks with cast iron main caps.A friend of mine owns and operates a custom crankshaft manufacturing shop in NC and nitriding is his biggest reason for rejected parts.I'm not saying it can't be done.I think about the most I've paid for a used honda crank was $125 and that was a gsr.You can get b16 for almost nothing and ls for $50 to $75.
Glenn

 

yes i fully understand what ur saying, and i understand the diff between the aluminum and iron blocks.... everyone has there own lil nitch when assembling a motor and what tricks they use, i jsut never had a problem with this at all...

yes we are limited to bearings size but when the crank is ground to match the .25mm bearings being used is not a issue so if i wanted to run a lil more clearance i would ask my machinist to measure and work his magic , yea dont get me wrong cranks are readily avalible its jsut we have it already, and we will use the **** out of someting till we need to change to a newer part...

now with the 125.00 invested into that used crank ur need to get it cleaned up and balanced and polished either way, ur close spending same amount of cash, what ever process i can find to make my rotaing assembly stronger, is strongly taken into consideration....

thanks for all the info, just wondering if any one has ever had any problems or if this has ever been topic of disscusion....

 

I never wanted to fumble with color coded bearings and plasti-gauge, so when my trusted machinist suggested that oversized bearings and ground cranks was the correct way to know your clearances, I did it without a doubt.
I've only done it on two motors (No problems whatsoever) so far, and I won't be doing it any other way unless I have a problem. It's security knowing exactly what kind of clearances you're running, and I like that.

I've also tried to explain this method to a couple people and they think I'm crazy or something.

 

grinding a crank is a sorta a last resort, when it is hurt and needs to be fixed... it just takes a lil time to measure everything and get the correct parts but its easy once u get the proper measuring tools....