Basically I dropped my parts off at my engine builder, and even from 10 feet away he said my crankshaft needed to be machined when I brought up micropolishing it. He got up close and quickly said yup for sure needs to be machined, I did notice there was some "rings on it, some you could swear you felt with your fngernail, but barely.

At the time I was going over everything so I was just like yup, lets do it. I didnt even ask the price. I know he didnt start it today and has to send it out to be machined.

Im at a loss on what I should do, let him machine it and buy new bearings. Or source a new hopefully OK crank that needs no work, and use the standard acl race bearings that I already have, ebay and local CL didnt show any cranks though, so I dont know what to expect to pay for a used one, and how to verify its ok, but I also dont know what hes going to charge to do the machining

What do you guys think??

 

Toss the crank and get another one. Can't machine a Honda crank

 

yeah i'm not a fan of turning cranks....

I wouldn't care much about using OS bearings & turning the crank if it was for a simple rebuild where it won't see high revs... sure go for it..

 

 

To be clear .010" is alot to cut away. The rule is simple, if you spin a bearing the crank is usually trash. But if you want extra oil clearance, you can safely micropolish half a thou no problem.

 

So you would say being under spec by .0001"-.0005" is ok and safe for a crank?

 

What's "under spec"? Do you mean out of round?

 

Under the minimum spec for the diameter of the journals. Or were you saying take off a half thousandth as long as it's over the Honda minimum?

 

What you are asking makes no sense. You can take off as much as you want as long as you can get the proper bearings for it. People forget that Honda cranks are forged and go through a different hardening process. When you have them turned down, you start to get close to that hardness boundary. Soft crankshafts can't handle the abuse and wear out extremely prematurely.

Regardless, I have NO CLUE why this is in the Forced Induction forum. Too many people have been cluttering this forum with garbage lately.

 

Anyone run a turned crank that failed because it was turned down?

OP, try using an ACL .001" undersize bearing. You can stick them in the mains and/or rods and see what the ID is. Then have the machinist take off only what is needed to get the bearing clearance you want. The surface will be cleaned up, the journals will be straight and round, you'll have the exact bearing clearance you're looking for, and it will only take off about 1/3 the thickness of a sheet of plain notebook paper.

BTW, polishing for clearance is a major no-no. The journals get out of shape (bell mouth, barrel, or tapered). Grinding is a much better solution. I tried to polish .0008" out of a crank before and it did not turn out well.

 

So I should let my machinist go for it or cancel and source a stock untouched unspun crank??

This is no high HP build, only 400whp at the very most

 

I would.

 

mods need to make a engine building section.

 

figured alot of people that build motors to take forced induction, have probably dealt with crank inspection/machining

 

I have a good gsr one. Pm me

 

single cam

 

400whp single? Yeah, get a new one. They are cheap as hell anyway.

 

Again, it depends on how much. Ive polished for clearance before. I wouldnt try to remove more than .0005" by polishing but sometimes you have to to get proper oil clearance.

 

yup get a new one. i made a mistakevbuy having my machine shop turn my crank . spun a rod bearing on the dyno.

 

There are better ways. If you need .0005" more clearance, you probably need different bearings. For instance, if I got .002" clearance with std ACL bearings, I could throw in a half set of X's and get .0025". I polish a crank for surface treatment only, not for clearance, but to each his own.

How does a turned crank cause a rod bearing to spin? You probably didn't have enough bearing clearance or some other oil system problem.

 

This was with HX bearings so I had no where to go. Im not saying its ideal. Im saying its fine to do - If your machinist can keep it round.

Agreed, you cant blame a spun rod bearing on a turned crank without more evidence. This is how these myths get started.

 

Either way would work.
If you could seriously hang a fingernail in the groove then I would definitely trash the crank and get a different one. Doesn't sound like yours had gone that far and was just light surface damaged.

Consider micro-polish if you go with the option of a different used crank - just to clean it up in it's old age.

 

Ya I stopped the machine work on the crank before he got to it thankfully. I probably would have let him do it had I not already bought standard main and rod ACL race bearings, so Im just going to hunt for a mint crank and check it well before purchasing

My last option would be a brand new oem one from honda, for $700. Which honestly doesnt seem HORRIBLE to me, but Im going to try and source a good used one first