Correct Torque For Rb26 Crank Bolt

[Shaun]

Hi,

Im just about to install an ATI harmonic balancer on my RB26, and i was flicking through my engine (workshop) manual and discovered that there were two vastly different torque recommendations for the 30mm crank bolt.

There is an exploded view diagram of the RB26, and it has 446 - 544Nm (45.5 - 55.5Kg-m) with an arrow pointing to the crank bolt. However, when you read through the step by step instructions, it says "Tightening torque: 142 - 152Nm (14.5 - 15.5Kg-m)" in relation to the crank bolt.

My manual also has the instructions for the RB20 and RB25, and the recommended tightening torques are all 142 - 152Nm.

I cant see why the torque for the Rb26 should be any different, let alone almost 3.5 times that of the other engines. Its a massive amount of torque; that means you've gotta apply about 27Kg of load on the end of a torque wrench with a two meter handle!

Im wondering if its a typo in the manual, and the correct torque is the lesser of the two. If anyone could shed some light on this it would be appreciated; especially those who have had experience in installing these balancers on RB engines. Its a pretty important topic i reckon, as its an engine destroying problem if anything fails down there.

I wish i could supply some pics, but if anyone else has a manual could you verify this for all of us. I got my manual off a forum member who sold me a disk; i cant see why i wouldnt have originated from a Nissan maunual.

Thanks,

Shaun.

Edited July 6, 2008 by Shaun

[murrayis]

I have the same in my manual

[Shaun]

Yeah, thats the same diagram as mine. You'll notice that in subsequent pages it recommends the 142-152Nm. It would be good to clear this up, as im a bit nervous about putting that much torque on the bolt.

Ive heard that you've gotta put the car in 5th and have someone with their foot hard on the brake, then use a stupid long handle to get the 500Nm. Apparently it sounds like the gearbox is going to let go under the load!

We need some engine builders to shed some light.

Shaun.

Edited July 6, 2008 by Shaun

[GTR1993]

The guy who used to build all the motors for kier wilson says he used to hang off it with a massive truck style torque wrench to get the torque in the manual... be interesting to know.

[Shaun]

Yeah. Id also like to know the best method of stopping the engine from turning. Is putting it in gear the best? It seems to be the only way, unless youve got access to the flywheel.

[Cubes]

Permanent Threadlocker + big breaker bar and hang off it is how I've always done it.

I drop mine in fourth gear with the hand brake on; never had issues with it moving.

I've always figured 4th would be the strongest gear 1:1; Don't like the idea of forcing 5th even though I'm probably only able to get 200-250nm in to it and no doubt the motor makes more at peak torque.

[GTR1993]

If you wanted i wonder if you could make a dummy solid starter motor or would it damage the teeth on the flywheel.

[Bumblebee]

im an engine builder and mechanic by trade

500nm+ is very wrong...

u would snap the bolt or the destroy the thread.. 142-152nm sounds about right and i wouldnt use threadlocker either

[skylinekid]

544nm would probably snap the bolt......

Edited July 6, 2008 by skylinekid

[GTR1993]

For comparison the 2JZ is 324Nm for the harmonic balancer bolt

[Bumblebee]

the last time i took the bolt out of my rb26 when i did the timing belt, it was on so fkn tight... ridicuous..

i put it back on and tightened to 156nm.... and then when the turbo popped and killed the motor... i STILL couldnt undo the bastard! lol

its like it tightened itself!

[Cubes]

Why no threadlocker?

Doing mine up to basically as tight as I can. 200nm or so with thread locker its fairly easy to remove with a normal breaker bar.

Onyl reason I've used threadlocker is every crank bolt I've pulled has had some on it. Be it from factory I'm unsure; Multiple RB30e, 2 x rb20det's. Given the age I'd say they have all been apart prior.

[Shaun]

im an engine builder and mechanic by trade

500nm+ is very wrong...

u would snap the bolt or the destroy the thread.. 142-152nm sounds about right and i wouldnt use threadlocker either

Im with you mate. Over 500Nm just sounds too much. I dont think my 350Kw engine even makes 500Nm of torque. Imagine if you snapped or stripped the bolt inside the crank! What a fcuking nightmare!

As for undoing it, ive heard that you can use a 300mm breaker bar and rest the handle on the radiator support, then crank the car (with injectors disconnected or something like that), so that the engine turns but the bolt doesnt. Do you think thats dodgy?

Anyone else with opinions or experience?

Shaun.

[rinmak]

I would invest in a decent impact gun and compressor guys. You will end up using it for lots of other jobs so its worth it

That way you can even have the car in neutral and crack a bastard tight crank pulley bolt without the engine turning one bit. When it comes to tightening just a few seconds with the gun and its all done. Should always double check it with a breaker to be sure however.

[GeeTR]

Strange, 2 pages down from that diagram, theres this...

Is that 446Nm for the crank pulley bolts?

Edited July 7, 2008 by GeeTR

[Gav]

What size is the bolt? From an engineer's handbook that I have, the yeild stress limit for a 20mm grade 8 bolt is ~ 550 Nm.

So if the bolt is 20mm or larger, then the higher torque value is possible.

[rinmak]

Its a 27mm from memory? Well I know an RB25 one is at least.

[Shaun]

No its 30mm across flats. Im not sure of the diameter of the shaft, but id assume its greater than 20mm.

GeeTR, i havent got that diagram in my manual at all.

Shaun.

[SysLink67]

I was thinking of doing it this way for my build. what PSI would you set on compressor? also would you use a torque wrench to test the bolt afterwards?

threadlocker?

cheers

rob

I would invest in a decent impact gun and compressor guys. You will end up using it for lots of other jobs so its worth it

That way you can even have the car in neutral and crack a bastard tight crank pulley bolt without the engine turning one bit. When it comes to tightening just a few seconds with the gun and its all done. Should always double check it with a breaker to be sure however.

[Beer Baron]

there will not be many regular impact wrenches that can deliver 500Nm. some people use a special gun with a reduction gear to get the required torque. as for whether or not it's correct, I'm not 100%, but lots of people that I know, who are 'in the know' tell me it is. I do also know I've seen a fair few RB26 balancer bolts come loose, no doubt they were not tightened 'enough'. mine has been one of them.