Crankshaft Grinding

[TriniGT]

Hi people, once again I have a question. I got a second hand crank from a friend that replaced it for his build, it is an R34 crank 05U on the crank and the engine had a spun bearing. I got the crank checked and the machine shop said that they may have to remove .010-.020 on the rod journal and at the same time do all to measure up. They said that the mains are all fine, what I want to know is if I have the crank ground can I get rod bearings that are .020 oversize? I spoke to one person and they told me that they only come in .010" nothing more, do I have an option for bigger sizes in the rod bearings? Let me know ASAP so I can know if I need a next crank, reason I took the crank in the first place is that it already had the long snout.

Jason.

[SteveL]

They said that the mains are all fine, what I want to know is if I have the crank ground can I get rod bearings that are .020 oversize?

The journals are undersize when the crank is ground, but anyway I'm fairly sure the first undersize available is .025, so you should be fine. Someone else will be able to confirm or otherwise.

[maximajim]

To be clear you require 0.020 INCH oversize? The largest I'm seeing the FAST is 0.25mm which is about 0.010"

[bubba]

.010" is .25mm which is first undersize, that's what I'm running on mine. I'm using NDC bearings and I'm pretty sure there were more size after .010" and ACL should be the same..

[skidkid]

I've ground a few cranks before. Did you have crank checked for straight aswell because I reckon you would be real lucky if crank wasn't bent. Means it will require a grind all over if not to bent. Doesn't your machine shop supply bits? Have you googled for 'ACL bearings' site?

[TriniGT]

Yes I was looking on the ACL site but I wanna make sure that I can get the bearings before I go ahead and begin the repair process. Seeing that people are suggesting it is possible to fix it then I will go ahead and get it done and order a set of bearings based on the size after machine work. This is going on a spare RB26DETT that I am going to be building up. It is getting some CPs and rods. Will let you know how it goes and I will contact ACL tomorrow to get a definite answer.

[TriniGT]

Wait it is Friday over there already, damn, it is 12:00AM over here in Trinidad (Thursday night).

[bubba]

Best to get the bearings your machinist suggests, then give them to him BEFORE he grinds your crank, that way he can mic up that specific set of bearings and grind to suit.

Edit: 1pm Friday here.. and I knock off in an hour

Edited March 13, 2009 by bubba

[skidkid]

I finished at 12 today!! Running at 2 beers per hour.

[murrayis]

http://www.aclperformance.com.au/NissanRB26DETTBearings.htm Is the link you want, the bearing sizes are metric.

First line of sizes is STD then 2 oversize bearings to suite a ground crank.

But like the others said get the bearings they recommeneds then take them to them and get them to machine the crank to suite the bearings.

[T04GTR]

acl do 10 and 20 thou in race series, ndc do them up to 30 thou. just look at sr20 ones, there the same. just have to buy 2 sets..

you can also have it offset ground to remove less but give a 10 or 20 thou stroke increase wich is f**k all.

[TriniGT]

Thanks a lot for the responses. Should I worry about removing the nitride coating on the crank. I have read that removing the coating causes the bearing to spin very easy, can someone confirm that has ground their crnak and has been running it for years?

[TriniGT]

Just got confirmation that the crank is bent and that it can straighten it and the mains will have to be ground .010" and the rod journals .020". Your thoughts on this and has anyone ever heard of straightening the crank, the shop said they have a unit specifically used for this process. This is news to me.

[skidkid]

I have straigtened a few with success and broken a couple aswell. You may be lucky. Make sure they cracktest it for you before they grind it!! Never used to worry about re-nitriding and don't think it caused a problem. The decision to go ahead rests with you though!!