having the crank polished good or bad?

[joescool2008]

I've read the stock crank has a nitride coating and that it is bad to have your crank polished because it removes it. I know the coating helps dissapate heat and galls oil also. However, I'm rebuilding my bottom end and the crank had enough wear i could feel it with my nail. So was polishing it the right thing to do? I know other engines don't have that coating. So what I'm asking is will it hurt me at all?

 

[TurboDSM90]

I've read the stock crank has a nitride coating and that it is bad to have your crank polished because it removes it. I know the coating helps dissapate heat and galls oil also. However, I'm rebuilding my bottom end and the crank had enough wear i could feel it with my nail. So was polishing it the right thing to do? I know other engines don't have that coating. So what I'm asking is will it hurt me at all?

About five years ago I sent buschur a virgin crank and block. They bored it .020 over, and took .010 off the crank. I beat on that stage 3 engine for a year.

Three years ago, I had two shortblocks spin bearings from an iffy machine shop. One of those blocks was the buschur stage 3 block. I got it back, and it spun rod bearings during the break in. The second one was a different crank, which was cut by the same shitty machine shop. It spun bearings a month later.

Two years ago I had a block built by another local machine shop (best find ever, Daves engine machining). I took them a new setup with new rods, pistons, bearings, mains, etc. The crank was cut .010, and the block was bored .020 over. That block lasted 16 months until it popped, the groden aluminum rods let go finally. I should add this was their first 4G63, and I used the same oil pump from the previous two motors that spun bearings.

This year I went back to daves again, and had another crank cut .010. I am looking forward to beating the snot out of this 4G.

So as long as you have a damn good machine shop do the work, and the clearances are set for the kind of abuse you are going to put the motor through, you will be fine.

By the way, I use shell rotella (non synthetic) diesel oil after breaking in the engine with walmart supertech 10-30 oil.

 

[joescool2008]

Thx for the info.

 

[Redwidow]

The Nitrate Coating Goes about .030 thousandths of an inch into the crank. When you cut a crank, you are taking off .010 thousandths of an inch, which still leaves .020 thousandths of an inch of nitrating. Polishing the crank only takes .0002-.0003 ten thousandths of the crank, leaving plenty of nitrating behind. Cut or polished cranks are fine, and are good for a good amount of power

 

[joescool2008]

I have 5k on my engine now after having the crank polished and using it in my rebuild, just figured I would post that and update this.

 

[donniekak]

The Nitrate Coating Goes about .030 thousandths of an inch into the crank. When you cut a crank, you are taking off .010 thousandths of an inch, which still leaves .020 thousandths of an inch of nitrating. Polishing the crank only takes .002-.003 thousandths of the crank, leaving plenty of nitrating behind. Cut or polished cranks are fine, and are good for a good amount of power

Polishing takes .0002-.0003" tops.

 

[BrokenTsi]

I had a machine shop cut my crank .010 and I made 600whp and trapped 132mph. I spun that engine to 9500rpm all the time. Best engine I ever had. Its still running to this day in someone else's car.

 

[Blackjet18t]

Polishing is always a good idea when reusing the crank after rebuilding the bottom end. It will remove any small imperfection burs and so fourth. It is also a good idea at the time to clean out the oil holes and "tear drop" the holes for better control of oil flow.

 

[Redwidow]

Polishing takes .0002-.0003" tops.

Thats what I meant, Changing to the correct info now

 

[Boostjunki84]

I had over over 40k on my cut and polished crank and had no problems. I just recently puttled the engine apart for another build, and everything still looked great. You should have no problems(as stated above) as long as the machine shop did quality work.

 

[TSIfreek]

Polishing does nothing to the coating. The coating is supper hard and the only way to remove it is by having the crank machined for undersize bearings.
Bring it to a shop that can polish it correctly for you they have special equiptment and expereance in doing so and its super cheap..