bearing sizes?

[Boostedexcel]

If I'm grinding he crank 10 under, what size rod and main bearings do I need?

 

[gthompson97]

.10 over, to compensate for the .10 under on the crank.

 

[gurmanator]

people are going to tell you not to grind the crank but .10 is safe(.10 over bearings)

 

[blackGSX2g]

I would never grind the crank from a 4g63. Once out of spec, you should replace it. The Factory Service Manual states that a special surface treatment has been applied to the crankshaft and it SHOULD NOT be machined to an undersize. With the low cost of a spec'ec crank, I'd shop around and find one from a junkyard or from someone on the boards. Thenk take it to a machine shop and have them mic it, no cutting.

That being said, if you ignore my warning and still choose to grind the crank. If you take .010'' off of the crank, you will need these .010" OS bearings. I would also have it balanced after removing the material as well.


http://www.slowboyracing.com/more.php?id=1095&

 

[Arod]

You would actually need .010 UNDERSIZED bearings. The crank journals get smaller when it gets ground down.

 

[blackGSX2g]

You would actually need .010 UNDERSIZED bearings. The crank journals get smaller when it gets ground down.

But the more you take off of the crank, the more you would have to add to the bearing to keep the same clearances. You need OVERSIZED bearings on an UNDERSIZED crank.

 

[bryanwheat]

The bearings are technically oversized, but they are called undersized bearings. I have ground one to 10 once, and had no problem with it, i put over 50k miles on the motor, never had another bearing problem after that. The coating is a nitrate coating to give extra strength to the (steel) crank, which is already very strong. I wouldn't go over 450 ho on a ground crank, but you should be fine under that. Good luck

 

[dnhieu]

okay heres the story. im rebuilding my n/a 6bolt and the crank that was in it was a little scared from bearing wear. i didnt think twice about asking before hand but i had it turned and it came out they needed to take off .020 on the mains and .010 on the rods. every thread i read tells me im flirting with disaster. to make things worse i just paid 100 for the bearings, 125 for a balanced rotating assembly and 90 to have the crank turned and balanced (so the crank has been balanaced twice). i have been reading so many threads that my eyes hurt and i cant find anyone who is using a turned crank past .010 over stock. out of the numerious threads i have read i have found 3 people stat that every time they turned a crank it ended up breaking. i called slowboy about their "remanufactured cranks". they say that they turn the crank and sell them. i was told they only take off .010 on the rods and the mains tho. sorry for the story but im kinda in a pretty big bind now. it sucks i got all this money raped up in this crank and ill have to pay for it all over again


also i read that some people are renitrating their turned cranks and getting good results. if anyone knows where i can send my crank off to, to get nitrated that would help alot.

thanks tuners
david

 

[Defiant]

It might break, or have premature journal wear. The factory says the cranks are non-serviceable, and I don't look at the question beyond that. Odd that your machinist didn't know this.
However, since it's done, I suppose go ahead and run it. It may never give you a problem, depending on what you intend to do with it.

 

[Boostedexcel]

What is the size is mm?

 

[Slowboy]

What is the size is mm?

.25 mm

MGH

 

[99gst_racer]

Yes, as Mike stated, .010 is equal to .25mm. You will have to order your bearings with a .25mm oversize.

Clevite 6-bolt part # - MS2076P25MM
Clevite 7-bolt part # - MS2039P25MM

 

[gurmanator]

the nitrating process penetrates .20 to.30 into the crank... .10 is safe for a grind.Have the crank "mic'ed"(see what your clearence is).If they grind the crank .10 under then order .10 over bearings(rods or mains).

 

[Defiant]

I have always wondered where this info came from. Any pointers to where this data can be had ?

Well, nitrating is done to hot dog meat.
Nitriding is well-explained herein:
http://www.dsmtuners.com/forums/showthread.php?t=137911