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I think I ordered the wrong bearings... .025 vs .25 for 10 over crank

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darknezz7

Proven Member
571
80
Mar 30, 2014
Eugene, Oregon
Pretty sure I have answered my own question but I want to confirm...

I asked the shop to do the crank .025mm, so that is what bearings I have.

Well I just noticed the tag on the crank says 10/10

Read this:
".25mm are the undersize bearings that will involve machining of your crankshaft. .25mm bearings are also known as .010 which is 10 thousandths of an inch. .025mm oversize are bearings for an engine that is slightly worn and you don't want to machine the crankshaft. I would machine the crank and get the .25mm undersize. Then you will have a fresh starting point. I am shooting for 600rwhp with my setup and I have my crank .25mm under."

So I need the .25 bearings not .025 bearings?

acl tri metals by the way...

I'll go ahead and plastigauge too.

But this is gonna suck if I have to get another set of bearings, I just installed and torqued down crank today...
 
If they cut the crank down 0.25mm, then you will need bearings to accommodate.
 
Thats what I am trying to confirm though, when it says 10/10 on the tag for the crank its meaning I need the .25 mm bearings?

I just feel they should have told me this because I asked if the crank would polish up to .025 bearings. When they said it was gonna clean up I ordered those bearings. But I think by that they meant it had to be cut for .25?

The mm and in thing gets confusing.

Mad now, $120 bearings wasted.... I still want to plastigauge to be sure, but it will probably be like .07mm way too much.
 
Just went through this on my block. Mains were a little on the high side and after ordering STD ACL Race bearings my clearances were .0035" when I wanted 2.5 thou. Ordered the -.025mm which is the same as saying .001" thicker for less clearance. This tightened things up perfectly without having to do a full line hone with cutting down the main caps. Instead, they just touched up the ML bore and made everything even.

The downside to a cut crank is that it takes away the factory nitriding process. You are building a 200hp per liter motor which is race engine territory even if considered mild in a 4G63. If you can avoid cutting the crank and can polish it to where the -.025mm bearings will bring you back to proper clearance then do it. Otherwise you'll have to cut it down .010" (.25mm) and use -.25mm/.010" thicker bearings. Won't be the end of the world but I wouldn't push it to 500hp+ personally...
 
Also, the race bearings do not have less surface area, they are harder. The softer Alumaglide style bearings that aren't the Tri-Metal will allow for dirt/debris to get inbetween the crank and bearing without as much damage. A Tri-Metal is stronger and does not tolerate such debris. It will eat right into the crank and is not forgiving. Lots of articles will say not to use race bearings in a street motor but again, you're not building a street motor you're building a high winding performance engine that needs the strength and heat dissipation qualities the nicer bearings provide. I'd bet 85% of the built motors here that run on the street are on ACL Race, and the King XP is a very similar Tri-Metal race bearing that is of equal quality. I believe the Clevite 77 does not offer the same Tri-Metal structure they used to unless you can find older stock. Don't quote me on that though...
 
Thanks for the info, I know about the opinions on cut cranks, it was heat treated after at least, not too worried about that.

So I wonder if the car should have had the .025 bearings all along, the first build I had the shop polish the crank, balance and assemble the bottom end, I gave them STD sized bearings, I never got a sheet to actually know the clearances.

This time I'm doing it myself, to learn, save money and hey whats worst that can happen? Another rebuild.

Im still on the fence on type of bearings, probably just stick with acl race.

Anyone know how much hp the aluglides can handle?
 
I forgot to take a comparison pic but, acls look like piles of dog crap to the kings imo. I know the acl's are the color they are from tri metal and heat treated, but they had rough edges, didnt sit in the caps as well, the small scratches on mains straight out of package. As someone also said the Kings also have far superior oil groves, theres extra ones on all the bearings plus 3 on the thrust while the acl has 2, I think the holes were actually bigger too. Now I really wish I would have taken a comparison pic because the photo above of that I ordered is a stock and not quite what mine looked like.

Anyway very happy with them especially for $50, will upgrade to the Xp's next year. In the future it will only be King for me.
 
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