WTF: RB30 crank damage (pics)

[ST240]

So i pull the harmonic balancer and goto pull the timing pulley and i notice its kind of loose.

I finally jiggle it off and i see this:



Any idea what the hell happened? Looks quite severe. You dont just mash through a keyway like that easily... There obviously had to be a difference in torque on the crank between the rotating assembly and the timing belt for something like that to happen.



I dont think id trust the timing gear again...



Whats left of the pillaged key.

I think i can save the crank by milling the keyway straight through and making custom keys. There was no evidence of this at all when the harmonic balancer was on. Everything seemed tight and the bottom end spun nicely by hand. Any ideas anyone? .

[robbie2883]

that's crazy....my only educated guess without knowing the history of the motor or being able to see into the head and block would be some kind of temporary binding in the valvetrain somewhere. bad enough to twist the timing sprocket. but odd it didn't do any damage to the belt. maybe mistimed or skipped a tooth at some point and minor interferance between pistons/valves? i dunno...i would deff check the rest of the motor over good though..that might give you some answers as to what happened

[ST240]

that's crazy....my only educated guess without knowing the history of the motor or being able to see into the head and block would be some kind of temporary binding in the valvetrain somewhere. bad enough to twist the timing sprocket. but odd it didn't do any damage to the belt. maybe mistimed or skipped a tooth at some point and minor interferance between pistons/valves? i dunno...i would deff check the rest of the motor over good though..that might give you some answers as to what happened

Perhaps i should have been more clear. I bought the bare bottom end fully assembled with rod/crank/pistons etc still on it. No timing belt or head though. I mean you could spin the timing pulley bolt with a socket and it seems to be smooth.

[robbie2883]

well...no matter what something major caused that...weather it was major detonation or binding somewhere...doesn't matter. the big question is what else is effected. this is just me personally, but i would pull the crank and have it spun up and have the line bore checked on the block. i would also replace the bearings (at least clearance them and make sure they are in spec)...just for safety sake, and check the rings and pistons outside of the block. this may be a little anal...but i believe in taking your time and doing it right the first time. some might say all this is unnecessary and it may be...but i'm a better safe then sorry kind of person. what's your peace of mind worth to you?

[SullivanRacing06]

before you cut the crank check with a maching shop to see if they can restore the snout of that crank so itll support a new woodruff/key way key ,

[ST240]

before you cut the crank check with a maching shop to see if they can restore the snout of that crank so itll support a new woodruff/key way key ,

Thinking about it more i mean thats a huge impact on that thing to shear a key out like that. I'm hoping to hell that the whole thing, let alone the crank, isn't a write off.

On the other hand if everything is ok, I think a guy could mill that keyway right through and past a little and have a two part key that fits snug in there. I don't see any reason why that wouldn't work.

[Darius]

It shouldn't be tough to fix that crank, but WTF? is right! How could a timing belt hold that much tension without slipping a tooth to bend over a 3/16" thick key?

[240z4u]

I have seen similar scenarios where people used the wrong size key to replace one. For example a metric that almost fits the standard slot. The impact does what you are seeing.

I work on heavy equipment that has keyed pulleys, and I have seen that type of damage several times.

Evan

[S14-NEO]

i have seen similar damages to cranks like that before...what typically causes that could be any number of things...a few things do stand out to me other than timing, first and foremost...someone could have been int there once upon a time and installed a woodruff key that wasnt the proper size and allowed the crank gear to move just a tad little bit...over time it can wear away at the crank like what is seen in the pics you provide. another cause (less likely) could be that the harmnic balancer wasnt properly tightened and it could have been damaged that way, but it would have more than likely also damaged the harmonic balancer woodruff key as well.

[ST240]

Thanks for your input guys. I'm going to compare the key to the other one when i get home tonight. Although a few thou can make the difference so maybe it won't tell me anything.

I had an even better idea:

Assuming the crank isnt pillaged to all hell, machine another woodruff key 180 degrees on the other side of the crank. Since the timing gear is symetrical it will not affect timing in any way. Furthermore, the harmonic balancer will still be in the same position so timing again will not be affected. What do you guys think?

[240z4u]

That will work, but you will have to mark the timing gear as well.

[ST240]

Whys that? The engine doesnt care where the timing gear is... It cares where the harmonic balancer is, which would be in its original position (its keyway is fine). As long as the teeth aren't off (which is why i mentioned it was symetrical above) it shouldn't matter.

[Sil240]

Mark it for TDC there should be a dot on the gear

[robbie2883]

your idea should work perfect....i think what's he's getting at is to mark the gear for the timing belt. there is a tooth exactly 180 degrees across from the timing mark so just a little dimple to let you know where the to line the belt up with should work great. or count the teeth. i think it's 9 teeth to the right of top dead centereither way

[240z4u]

your idea should work perfect....i think what's he's getting at is to mark the gear for the timing belt. there is a tooth exactly 180 degrees across from the timing mark so just a little dimple to let you know where the to line the belt up with should work great. or count the teeth. i think it's 9 teeth to the right of top dead centereither way

Yeah, that is exactly what I was referring to. Thanks for clarifying.

Evan

[ST240]

Yeah, that is exactly what I was referring to. Thanks for clarifying.

Evan

You're right sorry, I understand what you mean now.

[Wiring Specialties]

The RB has an known issue with the oil pump drive keyway. The oil pump drive is much larger than the driving key on the crank. Created big issues with the oilpumps failing.Nissan fixed the issue for the 1992 RB26, if i recall correctly. So the RB30 had the same issue. When i built my engine, we made a crank collar for the oilpump drive.

So, with this useless fact aside, it is possible that the oil pump failed in the past or the owner went in to fix the issue and reassembled the pulley incorrectly.

St240 - you gota redo the oilpump drive or it will come apart under good load. Just a thought.

ThanksYury

[RustspecS13]

Ive seen a few VG30E's do that as well, its usually that pulley gets loose, or the woodruff key gets slop in it. I know some people lock tite it in place.

Its common enough that a machine shop can fix it for sure. I think they weld the worn away metal and machine it to fit the new woodruf key.

Really that short block is junk. Mail it to be so i can inspect it in person and I'll reimburse you for your shipping and time

~Alex

[gawdzilla]

The RB has an known issue with the oil pump drive keyway. The oil pump drive is much larger than the driving key on the crank. Created big issues with the oilpumps failing.Nissan fixed the issue for the 1992 RB26, if i recall correctly. So the RB30 had the same issue. When i built my engine, we made a crank collar for the oilpump drive.

So, with this useless fact aside, it is possible that the oil pump failed in the past or the owner went in to fix the issue and reassembled the pulley incorrectly.

St240 - you gota redo the oilpump drive or it will come apart under good load. Just a thought.

ThanksYury

that's all fine and dandy but the part pictured and in question has nothing to do with the oil pump or oil pump drive. you can't even see the oil pump drive in those pictures, nor is the oil pump driven off a woodruff key.

[eh?]

It's a sign you need to upgrade the crankTo this

RB34 doesn't sound that bad..

[Wiring Specialties]

Maan, thats pretty. A pretty penny it is.

gawdzilla - i know and thats why i called it useless bit of info. But, my second paragraph says that with these oil pumps failing often, someone could have gone it to fix the isse of replace the oil pump, and reinstalled the crank pulley incorrectly.

ThanksYury

[ST240]

That would be the only silver lining... The collar has been extended .

I'm gonna pull this mofo apart myself and check clearances myself . It looks to be ok... Although one counterbalancer has a few orangish patches on it. Anyone know what that means? Excess heat?

We'll see what they say about the crank.

[robbie2883]

orangish like oxydation or orangish like discoloration in the metal? typically overheating hot spots will look blueish/purple. can have some orange too....but typically you see the hot spots closer to the contact surfaces.

[ST240]

Robbie, thanks, it must be just oxidation then.

Ok so with everything apart, here are some pics. These pics were the worst i saw. Some were worn like this, some weren't:



Rod



Another rod.



Center bearing. Seems like its getting some thrust wear. In any of the above pics, you can't actually feel the "wear" with your finger nail, you can just see it.



Last but not least, i measured runout. I removed all the bearings except the outter two which made sense to me, otherwise the other bearings might interfere, effectively lifting the crank up when it is rotated, showing less runout than there actually is. It was only out about 1.5 thou, which is 3.8 mm. Happy days!

So my big question to you experts is: replace the bearings, or not? I'm no expert so I'm not sure to what degree the bearings are worn. All I know is they don't look super prestine haha. I guess I might as well while she's apart. Futhermore, it looks like quite the rigamarole to mic out all the bearings so i might as well do that with new ones.

[robbie2883]

i would most deff replace the bearings...at the very least it's very cheap peace of mind when it's already all apart. they look pretty anyway. the anti-friction surface is all but gone. glad everything else checks out....yes it was some extra work...but if you hadn't done it after it went in it would have always been in the back of your mind...WHAT IF!! lol

[ST240]

Yeah i convinced myself of that a few minutes ago too.

I'm gonna go with ACLs. But i dont get it. They don't seem to have all the grades like the OEM ones do. Does that mean i just buy them and take them to a machine shop and they rework the crank or how does that work?

[robbie2883]

well...typically when you buy bearings you buy stock, 10 over, 20 over ect....10 over = 10 thousandths thicker than stock. if you have not had to machine the crank or the block i would get stock.....then you set the bearings in and use plastigauge to check clearances....if it's all within spec you're good, if the plastigauge is not measuring out enough then you will need thicker bearings. you would take whatever the clearance tolerance is and subtract the measurement of the plastigauge and that would tell you how much thicker your bearings need to be. then you would have to buy another set. basically if tolerances call for say 0.025 (25 thousandths) clearance and you measure with plastigauge and end up with 0.035 (35 thousands) then you would subtract 0.025 from 0.035 and end up with 0.010 meaning you needs 10 over bearings. there is a tolerance in there + or -...so read the fsm and see what it calls for. hit me up if you have any more q's

sorry for the lengthy answer...i just like to make sure you understand

[ST240]

No, thanks i really appreciate it.

I was under the impression that the OEM rod and main bearings are mixed and matched from several grades (or sizes like you were saying). Because ACL only supplies one set of either std, .025, .25, .5 etc, so what i was thinking is you might have to buy every f***ing set to get it right lol, but maybe not, and i just need to do more research (ie read the FSM again).

But maybe you only need the oversize if you've had crank damage?

[Carl H]

Seen that happen before, the harmonic ballancer was loose and side to side play was allowed to develop due to lack of force on the crank pulley keeping the whole assembly sandwitched together.

[ST240]

Cool. Yeah im not too worried about it anymore. Havent had any time to take it to the machine shop yet, and work is about to get a whole lot busier so its gonna have to wait yet longer .

Found some piston damage:



Think I can reuse it? Just planning on getting this thing running this summer, going forged next summer.