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Rb30 Severe Crank Damage (pics)

ST240

By ST240,
in Engines & Forced Induction

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ST240 Enthusiast

ST240

Posted
Posted (edited)

EDIT: I must be clear; this is a shortblock that i purchased here in canada. I have no ideas about it previous running condition or lack thereof. The guy who i bought it from said it had excellent compression, thats all.

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:

SDC10761.JPG

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.

SDC10762.JPG

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

SDC10764.JPG

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? Is the crank salvageable?

Edited by ST240
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Neil Grand Master

Neil

Posted
Posted

Personally I'll bet the balancer bolt was left loose at some stage,,,the gear has moved in and out of the crank,,,killed a belt and the previous owned slapped it back together and sold it to you. That crank is in a bad way,,,normally I would be happy to fix it but thats very bad.

Neil.

ST240 Enthusiast

ST240

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Posted (edited)
:P . anyone have a crank?

I'm going to see if the crank is damaged otherwise. If not I am going to attempt to mill a keyway 180 degress from that set and i should be away.

PS: DiRTgarage can you please email me at andrem85 @ telus dot net and we can discuss futher. I can pm until i have a post count of 10 and i dont feel like spamming this great board up you folks have just so i can pm you back :D .

Edited by ST240
GTRsean Grand Master

GTRsean

Posted
Posted

Mine did that from a bolt not being tight enough. Had a new crank keyway milled into the opposite side (180deg) when I was rebuilding my eng.

No probs, just be aware that the timing mark on the crank gear will be 180deg out.

ST240 Enthusiast

ST240

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Good to hear guys. Thanks so much for the replies! Glad im not the only one; and that the damage isnt the end of the world :) . I have the pistons out, working on the girdle right now. The rod bearings look slightly worn, but maybe its normal. I borrowed some telescopic gauges, a micrometer and a dial gauge from my machinist to measure it all up.

I'll post some pics up and see what you guys think.

ST240 Enthusiast

ST240

Posted
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Posted (edited)

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

SDC10767.JPG

Rod

SDC10771.JPG

Another rod.

SDC10774.JPG

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.

SDC10785.JPG

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.

Edited by ST240
T04GTR Grand Master

T04GTR

Posted
Posted

no. its 0.6mm

looks like its not had the oil changed for ages. or has had a lrg gas conversion and the oil has been nitrated. (acidified from the lpg and not using a lpg oil)

and yeah, loose crank pully. although ive not seen it happen on the timing gear, but rather the crank pulley key way.

it can be fixed pretty easily, you need to get a good quality ceramic tile. shape it with a angle grinder to make a dummy key. get a good mig welder and fill the dammaged part of the crank with weld, then linish it back to round and remove the tile, you will have a good strong keyway slot.

not ideal but provided the crank pully does not come loose again, will last forever.

ST240 Enthusiast

ST240

Posted
  • Author
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no. its 0.6mm

looks like its not had the oil changed for ages. or has had a lrg gas conversion and the oil has been nitrated. (acidified from the lpg and not using a lpg oil)

and yeah, loose crank pully. although ive not seen it happen on the timing gear, but rather the crank pulley key way.

it can be fixed pretty easily, you need to get a good quality ceramic tile. shape it with a angle grinder to make a dummy key. get a good mig welder and fill the dammaged part of the crank with weld, then linish it back to round and remove the tile, you will have a good strong keyway slot.

not ideal but provided the crank pully does not come loose again, will last forever.

I'd rather not weld anything at this point; Id rather machine a keyway on the other side. I think welding is last resort.

I made a typo. Its 0.038 mm no? Lol anyone else got an estimate? And to think we're trying to build engines here :) .

Futher to this damage, It looks like something got in one of the cylinders at one point:

SDC10791.JPG

But i think i can reuse that piston. What do you guys think? There was some slight scoring (you can just barely feel it with your nail) in the bore too upon closer inspection which I'm hoping can improved by honing. I don't know what amount of scoring is acceptable before you need a rebore. Can anyone comment?

ST240 Enthusiast

ST240

Posted
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reuse it?

at a minimum i would be binning the rod,s crank and pistons and starting with fresh items (good cond 2nd hand crank) with new rings and bearings, then you'll have a half decent engine...

Lol :) . I was just going to do a build on stock RB30E internals for a "low" ( :) ) power application for this summer then go forged/full build next summer. You don't think I should reuse anything?! That's a bit extreme no?

our12 Enthusiast

our12

Posted
Posted

Hi.

What you need to do is take crank rods pistons to a machine shop who know what they are doing. Explain your situation to them re rebuilding in the short term and have them measure everything up and be guided by them- ask questions re honing and bore wear. Ive seen much worse pistons used succesfully in the past.

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