Crank thrust surface scoring

[Drewster]

On a new build, Is it ok to have a little scoring on the rear thrust surface of #2? Will the bearing just make a matching groove or does it need to be perfect?
I will be turning to .010/.010 but the thrust surface is less forgiving at the shop.
Andrew

 

[Drewster]

Will this clean up?

 

[m233roller]

Don't run it that way as that surface must be SMOOOTH. You can have it turned but will need an oversized thrust bearing and I think they are getting damn hard to find.

 

[Lil Truck]

Oversize is still available in .010&.020
If you have problems finding some I have a set of Calico coated .010 on mains .020 on the thrust that I will sell.
I have the matching .010 rods bearings also.

 

[Jay J]

Don't run it that way as that surface must be SMOOOTH. You can have it turned but will need an oversized thrust bearing and I think they are getting damn hard to find.

X2! That roughness will just start grinding away the nice thrust surface on your new bearing, with more bad news to follow...

 

[earlbrown]

It needs to be measured before you can say whether or not it will clean up. Any other speculation is a pure guess.

 

[TRICKSIXPA]

I just got something like this done with my crank. Had the mains cut down and got a oversized Thrust bearing. King makes the main bearing kit. The thrust on mine was pretty bad so the machine shop got a .030 over thrust bearing with that kit. Both sides of the wall have to be cut down so it sits in nice and even.

 

[Drewster]

Can the machine shops take off say .003 and polish another .001 on the one side and keep the clearance in spec. Or just polish .002? Or is there no tool or technique to get the smooth finish on the thrust surface? If there is a thrust clean up technique, what's it called?
Would they use a lathe and turn it?
Andrew

 

[TRICKSIXPA]

I'm sure they could take off .002 on one side and .001 on the other. Would it work I don't know. As long as your within clearance on the thrust it should be good.
The bottom ones were the Mains I used.

 

[earlbrown]

It gets dressed on the crankshaft grinder.

 

[Drewster]

Earl, So do thrust surfaces get cleaned up every time the crank is undercut as a function of the grinding or do you have to ask for the thrust dressing? Looks from the pic that .002 off would do it and keep tolerance.
Lil Truck and Tricksix, Ive got another crank that the oversized bearing will work for, I appreciated the info and part numbers.
Andrew

 

[earlbrown]

It's up to the crank grinder on a case by case thing. It's hard to put into words but precision grinding it pretty much an 'art'.

 

[TRICKSIXPA]

The only issue is your NOT going to find a standard Main Bearing with an over sized thrust. So no matter what, you will have to get your crank's mains cut down regardless.

 

[Drewster]

yes planning on going 10/10.
Andrew

 

[3.8L V-8 eater]

As with many cases money sometimes dictates our choices when building...In the long run would it not be better to just get a new crank than to roll the dice with this one?? I'm sure you have thought about this but wondering what your thoughts are on wanting to fix this one?? As Earl said case by case basis but do you trust who is analyzing and making the decision?? They sell some reasonable priced steel stock stroke cranks that are external balanced...Good luck to you not trying to question your decision!!