Doing rebuild: Question on crank

[Eagle_Summit]

So a friend and i were ripping apart the motor that im rebuilding. The kid that had the motor before said he knew #2 cylinder was f-ed up but not sure what was wrong. So as i get farther into it we noticed the bearings were all shot to shit. I'm guessing it was the balance shaft that caused this, becuz on the front cover the balance shaft belt was all chewed up to hell and back. So there is a thrust bearing that is all f-ed up and the rest of the bearings are all wore away pretty much. Guess my main question is, does this mean my crank is screwed or not? Or am i going to have to ttake it to a machine shop and talk to them?

If you guys need some pictures ill take some.

 

[DSMatMSU]

prob going to have to take it to a shop.... i had 2 spun rod bearings.... but caught it in time that i didnt wear away at my crank too bad.... they just polished it....

as long as there are no deep scratches, or abnormal wear across the grooves... it should be ok.... it sounds like your bearings are pretty Fd up, but w/o looking at it, its hard to tell....

but if it is bad, get a NEW/USED crank... dont grind dsm cranks.... taking the outer hardening off = not good....

 

[Jake_16_1999]

Definetly take it in. I am rebuilding my 7 bolt and am having my crank polished before putting her back together, falls under the better safe than sorry venue.

Jake

 

[GSX_RCR]

Post up some pics.

Worse comes to worse, it's time for a 100mm stroker crank.

 

[pinknuggit]

but if it is bad, get a NEW/USED crank... dont grind dsm cranks.... taking the outer hardening off = not good....

not 100% true.. I've built some 4g63's with turned cranks, and none of them have failed.

If there is enugh hardened material on the outside .010" of the journal to where the crank would break if it wasn't there, then our engines shouldn't even be capable of idling without breaking a crank..
The reason people are breaking cranks that they turn is they don't balance them after the journals get ground. You're not going to take the whole nitride coating off of the crank unless you cut deep to about .030" or .75mm.

 

[diambo4life]

The FSM clearly states that a special surface treatment has been applied to the crankshaft and it SHOULD NOT be machined to an undersize.

 

[DSMatMSU]

alot of things CAN be done.... im sure it would work, and im sure many folks have had some good fortune with a turned crank....

but when turning a crank cost about 75+ bucks.... how much more for a new/used one???

but its up to you

 

[1fast97gsx]

alot of things CAN be done.... im sure it would work, and im sure many folks have had some good fortune with a turned crank....

but when turning a crank cost about 75+ bucks.... how much more for a new/used one???

but its up to you

well slowboy sells some cranks that were cleaned up but they want $350 with bearings. If you turn yours and buy bearings it should cost $200 - $250 max.

 

[97turbodsm]

I am rebuilding my 7 bolt, and I just got my crank back today from getting turned. Now I am hearing that you shouldn't turn them. Am I in for trouble??

 

[Maglin]

Personally I wouldn't have a crank turned and expect to apply over 400 HP to it and it be reliable.. If you spend a bunch on your internals and go cheap on your crank you could just get hosed... A polishing shouldn't remove really anything and is the best course of action if possible... If a new crank was in order then go Stroker if you haven't purchased pistons yet and if you have the extra dough get it knife edged and reblanced.. It's a little costly but if you are going with a light weight flywheel, BS removal and lightwieght crank pulley all it will do is take off more recipacating weight... A definit must for you hard core auto crossers.. Also oil scavaging off the crank will be improved a ton...

 

[half-cocked]

I am rebuilding my 7 bolt, and I just got my crank back today from getting turned. Now I am hearing that you shouldn't turn them. Am I in for trouble??

Research this a little more, I thought I heard that 2G cranks are not nitraded and I check my FSM and it didn't say anything about NOT grinding it like the 1G's does.

 

[92redman]

Personally I wouldn't have a crank turned and expect to apply over 400 HP to it and it be reliable.. .

What is wrong with a turned crank? V8 engine builders turn down their rod journals quite a lot in order to create a stroker crank or to lighten the journals. Taking off .010" will not effect reliability, but it should be stress relieved and rehardened.

Personally, I would be more worried about a bent crank then scored journals. Send it out to get it checked.

 

[Defiant]

What is wrong with a turned crank? V8 engine builders turn down their rod journals quite a lot in order to create a stroker crank or to lighten the journals. Taking off .010" will not effect reliability, but it should be stress relieved and rehardened.

These aren't V-8s. The DSM cranks are nitrided. Much more than a polish will get through the treatment.

 

[92redman]

These aren't V-8s. The DSM cranks are nitrided. Much more than a polish will get through the treatment.

That is why I said it should be stress relieved and rehardened. It must be stress relieved first and checked for straightness or it may come back bent and you can't bend a hardened crank or it will crack the surface.

Also, depending on how the nitriding process was done, it could go upto .025" deep. I have no idea how deep the hardening goes on our cranks, though, but I don't think Buschur would be machining cranks if they weren't strong enough.

 

[Mike1992]

The crank in my 6-bolt turbo motor is pretty scored, I think im gonna have to have it turned pretty good.

 

[half-cocked]

Non-turbo 6 bolt cranks were not nitrided.

 

[1fast97gsx]

Non-turbo 6 bolt cranks were not nitrided.

and they probably won't hold up to as much abuse either ..

 

[92redman]

Non-turbo 6 bolt cranks were not nitrided.

How do you know? The only ways I know of to tell is taking a file to the throw or use a copper-ammonium solution that changes color(red).

 

[Mike1992]

I said Turbo motor as in my 90 GST, Im getting ready for rebuild time, I pulled a main cap and a rod off and saw alot of scoring under the main cap, but nothing under the rod. I'll know more when i take it to the machinest.

 

[half-cocked]

I said Turbo motor as in my 90 GST, Im getting ready for rebuild time, I pulled a main cap and a rod off and saw alot of scoring under the main cap, but nothing under the rod. I'll know more when i take it to the machinest.

Sorry, I just made an assumption on that one.

And redman, I was refered to a mecahnic at a Mitsu dealership by the parts manager that stated he had been into DSM's before he bought his Evo and when I asked him about the nitriding the first thing he asked me was if it was a turbo or not and if it wasn't they didn't harden the N/T cranks.

 

[alexg1323]

Non-turbo 6 bolt cranks were not nitrided.

i dont think thats true. Im sure they probably all go through the same process. What makes you say that

 

[defrag010]

Simple. See if a new replacement crank for a non turbo has the same part number as the one for a turbo.

 

[alexg1323]

https://www.mitsubishiparts.com/oe_parts_catalog.html well if you look here mitsu only sells 1 crank for the pre may 92 2.0 motor regardless of whether or not its turbo.

 

[Mike1992]

https://www.mitsubishiparts.com/oe_parts_catalog.html well if you look here mitsu only sells 1 crank for the pre may 92 2.0 motor regardless of whether or not its turbo.

Thats odd, because i know for a fact theres an alignment dowlpin for the flywheel on the turbo crank and not for the NT 2.0. (6-bolt of course)

 

[half-cocked]

I am just quoting what I though was a reliable source, I figured they guy works on Mitsubishis and he said he has rebuilt a few DSMs guess I better watch who I quote, I apologize.