Crank Damage

[Psymon]

I recently bought an RB25 to put into my R32. I was pulling it down last night to have a look at the condition and give it some new gaskets and timining belt etc. When i pulled the harmonic balancer off i noticed that one side of the keyway seems to have been flogged out. (see pic!)

What's the easiest way out from here? Is it repairable? If so is it safe/reliable to do so? Or am i better off tracking down a good condition crank and just replacing it?

Thanks guys!

[The Dan]

There is no way to repair that without risking problems later on. If you use it without repairing or replacing, you will regret it later

[DVS JEZ]

spewin, one of my trucks just spat the crank pulley and the key way isnt quite that bad, hopefully i can fix it without a new crank or the truck is going in the bin...

[Psymon]

spewin, one of my trucks just spat the crank pulley and the key way isnt quite that bad, hopefully i can fix it without a new crank or the truck is going in the bin...

Large bin or small truck?

So it's not really viable to fix this? Inconvenient!

[Beer Baron]

it can be fixed. the keyway just locates the balancer. it doesn't actually turn it, that's done with the force of the bolt holding it on (just like wheel studs don't turn your wheels the hub face does).

they get damaged when balencers come loose, without the bolt then the key is turning the damper and it just gets bashed to bits.

not many people are willing to repair them but herman at envy imports in sydney can do them. i've seen him do a few and all the one I know of are still living a happy life. talk to him about cost for repair and then figure out if it's worth doing vs a new crank.

Jez: he could probably fix your truck one too.

[Psymon]

I don't suppose you'd have a contact phone number handy Richard? I'm out in the sticks so it would involve freighting it in etc.

[Dave.TAS]

Fitting a new key with epoxy or metal magic to take up the flogged out space, plus a new balancer, will work. For how long I cannot say, but I repaired a ca18det in the same way and it has since done 5000km at 180rwkw without a problem.

Still, not ideal, but since the filler material has no where to go and as long as the bolt is tightened properly it works.

On a ca20 junker I replaced balancer and key and epoxied, that's since done about 10000km and been apart twice for headgaskets haha

[Psymon]

Would a new balancer really be neccessary after a repair? I just went out and had a look and the woodruff key is still a nice fit in the balancer. No movement at whatsoever once it's in there.

[Dave.TAS]

Then probably not, all the ones I had issues with have been worn in the balancer

[The Dan]

Ok maybe I should re-clarify - yes you can fix it, there are many ways to fix it. There are no ways to fix it properly. If you rev it too high the balancer will come loose again due to the harmonic vibrations and microscopic movements and twisting of the crank. Heat will also play a part in it's demise.

Fix it, but know the risks if you do

[Psymon]

I understand where you're coming from. Since the car is still running fine with the current engine and i have the time up my sleeve, i'm leaning towards tracking down a crank in good condition. I do intend on leaning on this motor a bit so i'd like to do it right first time around.

[Adriano]

I recently had one repaired by a company called industrial hardchroming in Sydney, They weld it, then chrome it and grind, recut the keyway, only cost about $200

[SKiT_R31]

This is really common on RB30's, I've had 2 cranks with slogged out keyways. I just sand/gently file any ridge/warping then use some locktite liquid metal (it actual says for keyway repair on the tube) stick the keyway in and let it set, slip on the balancer and torque the bolt to a tasty 500nm (aka as hard as you can). $12 fixed.

Did this on my RB30DE which revs fast and high frequently (hi comp, cammed, short geared, lightened and balanced) and it has never had a problem.

Edited March 10, 2011 by SKiT_R31

[Beer Baron]

I recently had one repaired by a company called industrial hardchroming in Sydney, They weld it, then chrome it and grind, recut the keyway, only cost about $200

yep, same basic way as herman repairs his (he does have another little trick too). most will also need a new balancer as mentioned above as if they have come loose they tend to wear. the main thing is getting the crank snout repaired properly so the new balancer is a good fit. then with new keyway, new balancer bolt, new washer and new backing plate it should all go together nicely and live just like a bought one.

herman is at http://www.envyimports.com.au/contact_us.html

02 9907 4144

[badhairdave]

I'm with skit r31. It's a key way to locate the balancer, nothing else, and the damage isn't that bad, one side is still perfect so you can still line it all up right. If the slot in the balancer is flogged out then replace it.

If the crank was already out then yeah, $200 cheap fix.

But it's not; As soon as you pull that engine apart you may as well have thrown it in the bin and bought another 3 s/h short engines as you won't get change from 2.5k to have someone that knows what they are doing put the whole thing back together properly. Not some monkey that passes them self off as an engine builder.

[MrStabby]

To check I understand what's been said above and the bits i know - is this a good summary?

- the keyway is only use to locate the balancer during installation, and does nothing once the bolt is installed

- the only reason the balancer needs to be located is so the timing marks are in the correct location (ie it's not counterweighted or ??)

- so the only effect of a worn keyway is that the timing marks will be a little off

But if i understand Elite, he's saying the balancer will come loose again if the keyway is stuffed and the motor is revved high.

Que?

[Beer Baron]

yeah mate that's pretty much it.

I think ERD's problem with it is this. usually when balancers come loose and damage the keyway sometimes they damage the rest of the crank snout too and the balancer. in those cases just repairing the keyway wont help with the balancer fitting properly on the snout. fixing the whole surface properly and replacing the balancer is the way to go.

as far as the balancers being weight indexed to a certain spot I'm not sure, but I think they are not. each component from the factory is balanced separately. they are not actually a balancer anyway, they are a harmonic dampener and crank pulley. there is a slight difference between the two.

still I have no problem using a repaired crank as long as it's repaired properly and the balancer and bolt etc is replaced.

would I used a repaired crank as the basis for a mega $$ engine? probably not. but I had no problem revving my old one to 8,300rpm after it was repaired.

[The Dan]

That's pretty much it BB. The fact the keyway was damaged means the balancer had been moving around. This will either micro weld the crank to the inside of the balancer or it will machine down the snout of the crank. This means any new balancer that goes on or the old one, will not have enough or any interference against the crank snout. The amount of movement there when you are revving past 7k would scare you. The purpose of the balancer/dampener is to remove harmonic vibrations from the crankshaft. If it is able to move due to the bearing retainer or loctite material not being able to sustain high bonding strength for more than a short time, it will surely come loose again or destroy the oil pump.

I know people who have welded balancers on to cranks and not had problems. I know people who have repaired keyways and not had problems, I also see the ones that were apparently repaired correcty and have come unstuck. If it were my car and I had to choose, I'd choose to replace it.

If the repair is done by welding the snout of the crank, you also risk the end of the crank snapping off. I know people had done this without any problems but once again, I have seen the other side of the coin too. Why risk it. Cranks are not expensive and fairly easy to come by

[2gceffy]

I'd prob replance crank and just throw new bearings in at same time, it's all out and apart good opportunity

[MrStabby]

That's pretty much it BB. The fact the keyway was damaged means the balancer had been moving around. This will either micro weld the crank to the inside of the balancer or it will machine down the snout of the crank.

Ok so the OP needs to check the dimensions (snout OD, balancer ID, roundness) with a micrometer. If the snout OD is within spec then its reasonable to repair the keyway, if not, new crank. If the balancer ID is out of spec then just get a new balancer.

If the gap is a little bit more than spec, would it be possible to dodgy up some of the clearance with a locktite product?

Also, I'm guessing the crank should be annealed after welding (assuming its safe to do so) to really do the job correctly.