Bent Crank Shaft

[tacker]

just put my R32 crank into shop to have the oil pump drive collar fitted to tell me the crank is bent?

How do you bend a crank shaft, was running fine all bearings are fine and bearing surfaces are good too. it did lunch # 5 piston hence the reason its out but was running fine until it failed. Cant complain about the piston failure engine had ove 100 k on it and we were sort of pushing it a wee bit.

[giant]

hehe! we had a bent crank too! laws of physics my friend!

[giant]

i am no expert here, but i have been told that a crank tries to straighten out when reved hard or revved quickly it also tries to stand on it's end, on top of that they are only semi counter balanced.

[giant]

hows ya block!

[tacker]

very personal question there Russ! oohh BLOCK :-)

i had another of those laying around Squeeky Steves shop.... just waiting for him to call and tell me its warped or the flux harmonic capacitor has .3 degrees run out or such, that would make his day i can hear him gigglin now.

Get the feeling he dont like my fleet of RB26DETT's to much in fact he has renamed them FURKIN26DETT's i think i am just gettin closer to his pet EVO even had to use the excuse my tyres are 04's your are 08's

so in the market for a new R33 crank i guess

[giant]

actually i heard that excuse from him today!!haha

[bubba]

Straight six cranks are susceptible to bending purely because they are so long.

[**RB2530**]

Straight six cranks are susceptible to bending purely because they are so long.

Unfortunately it is easy to bend a crankshaft esp in a straight 6...If you lunched a piston then what may have happened is that the engine locked up suddenly on cyl No5 and the rest of it didn't want to...therefore something has to give..it may be bent but also a bit twisted..Just the inertia in the flywheel is enough to twist the crank if it is locked suddenly...

It will still run but the timing will be all over the shop...ie crank is bent but cam shafts are not...I say if you ever lunch an engine get a new crank if you can afford it..

[tacker]

hmm it just broke a ring land on number 5. I think that it is bent on the front where the oil pump drive is although i never felt any vibration and if the piston hadnt failed it would still be running around.

Very strange

[**RB2530**]

Yep that is strange...If you just did a ring land and the motor did not stop or sieze all of a sudden I wouldn't expect any torsional bend...Maybe the workshop dropped it...

[Blitz]

Nice work Chris, as least you popped the 26 in style

[blk180]

Nxtime has a billet Apexi crank for sale full counter mmmm very nice.

[Duncan]

meh you aren't trying, it took too long. I've know of 2, one in a motor where the bearing spun (not sure if that was cause or effect though) and another which was just road driven, eventually the bend caused the balancer to rub on the timing cover and bolt to loosen. not good for it really.

just grab another one, cranks are cheap and collars are easy enough to fit.

[Sinful]

it all depends how bad the bend is??

If its bent on the collar drive then it can be repaired fairly easily. If its bent half way down then grinding the crank if its only a couple of thou usually is sufficent enough.

Generally every RB26 crank that I see has a slight bend in it. Depends if the owner wants to worry/know about it though.

[Duncan]

indeed - i should have said we've re-used both the ones I mentioned. 1 was straightened, and the other just got 10 thou undersize bearings.

[tacker]

going to slap a new one in and use the old one in the spare engine we will cobble together from the reems of bits left over