# why is crank grinding bad on rb26dett engines ?



## scoooby slayer (Jun 13, 2009)

just curious why its a bad idea on these engines ? ive run a cosworth yb 2.0 at 472 bhp on a .25 crank grind to 7800 rpm and it was fine ? are the cranks only surface hardened and loose that when they are ground ? my engine may need a crank grind and im curious what my options will be without spending circa £1000 on a new crank. any info would be much appreciated. 

thanks
carl


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## R.I.P.S NZ (May 7, 2004)

who's says its a bad idea to grind a RB26 crank?


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## GT-R Glenn (Nov 9, 2002)

Sigh .....


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## R.I.P.S NZ (May 7, 2004)

New cranks arn't (or shouldn't be) around 1000 pound. there's nothing wrong with grinding a stock 26 crank, we grind stock 30 cranks and run them to around 1400hp and 10,000rpm at times.

Go for it and save your money for mapping.


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## hytech (Feb 26, 2003)

We grind RB cranks on a daily basis. If it's run a bearing sometimes the crank will bend. If it's to bad we bin them.


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## rasonline (Mar 24, 2005)

have a read here...
http://www.gtr.co.uk/forum/35988-can-you-grind-crankshaft-not.html


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## Adam Kindness (Jun 22, 2002)

so.... how much should you pay for a new OE crank?

We have out crank ground/polished after the last time it cought a bearing. It happened again on Thurs eve. Hard track use and likely oil starvation though.


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## paul cawson (Jul 3, 2003)

Nothing wrong with grinding a RB26 crank if it is done properly for example The crank is not bent, and the oil ways are cleaned after.
I had one done and it was ground over centre which meant the stroke was slightly increased on a couple of cylinders due to it being bent in the first place. So fit only for the bin.
Another was ground even though the thrust faces were worn out, my fault for not checking first but the supposed experts who did the machine work did not pick up on it either.

Also worth a mention is that you need a zero grade set of rods or how do you make up the differents with 0.25 shells right through. Which is why the mains should not be ground.

So taking all of the above into account I would never use a ground crank except for a cheap track/drag engine for myself that would be scrapped before the car was ever sold on.


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## G40tee (Feb 25, 2008)

Adam Kindness said:


> so.... how much should you pay for a new OE crank?
> 
> We have out crank ground/polished after the last time it cought a bearing. It happened again on Thurs eve. Hard track use and likely oil starvation though.


Adam,

When i was looking for one about christmas time i was quoted about £900 i think it was from RB motorsport.

Obviously the yen rate massively affects the price.

I ended up buying a good crank and jun collar from GTaRt in the end. Cost me less than half of a new one and was fine!


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## GT-R Glenn (Nov 9, 2002)

Good post rasonline 
8 pages of discussion on grinding cranks ....


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