Useful life of a crankshaft?

[Matt Conrad]

The crank in my Crossle 35 was in it when I bought the car about three years ago. I have no idea how long it has been in use or how many racing hours it has on it. The flywheel, to my knowledge, has never been in contact with curbs, etc., so I believe the crank hasn't seen that type of abuse. Both rods and mains are undersize.

My machine shop checked the crank for straightness and "wet magnafluxed" it. They found that it was true within .001" and had no evidence of cracks.

Should I have qualms about running this crank? Are there recommended guidelines for routinely replacing a crank with no apparent signs of distress?

[Jerry Sloot]

when the bottom end is torn down, that is the time to replace the crank. or phrase it this way: cranks are a disposable part. but then if you care to chance a crank failure, it's your budget and your decision to reuse it - i just hope that if and when it fails [cuz they do] you are able to figure out the fact that the crank was used was the cause - otherwise you just get to scratch your head and wonder as to failure cause and you spend a lot more money than a new crank would have cost... and just try finding new blocks.

[John Green]

Hi,
If it's been checked and was OK I see no reason not to use it. How did the bearings look are they in as new condition no need to replace and you save time on running in. When you have an off se if kerbs or anything hit the crank if so put the engine aside and check the crank before running it again.

Henrik

[KRD]

Changing the Crankshaft every time the bottom end is torn down is the poorest advice I have ever heard. The Crank will last through several bearing changes before it even has to be turned. If it still passes modern crack detection inspections and you know that it doesn't have several thousand miles on it,run it. You can afford another block,sleeved and all every 7-8 years because it's cheaper than a new Crank every bottom end tear down.Does that mean that Piston Rings have the same longevity as Crankshafts.
I think this guy got the same marks in Spelling as he did in Science. Stick to Driving.
Derek

[DENIS]

Anyone who is replacing cranks everytime the bottom end is torn down, please call me. I'll take the next two at a fair price.

[ucemotorsport]

Any cranks that Todd does not take, I will be happy to take off your hands and help clean up your shop. Unless you only take the bottom end apart every 10 years there is no reason to change the crank every time the motor is apart. I guess you can make racing expensive if you really want to.

[markD]

Has anyone had any experience with cranks that have had to had the thrust bearing surfaces remachined? I have one at the crank shop that they recommend building up this surface and then machining to specs. The cost is not prohibative and the crank crack checks fine.

[Greg Sibley]

Good question. I just decommissioned a crank that was otherwise in beautiful shape but has thrust surface wear beyond what can be taken up by oversize thrust bearings. The crank shop recommended welding up and remachining but I didn't do it, being leery of induced stresses.

[Paul Spurgas]

I've been told that re-building the surface for thrust washers on cranks is ok
for street use; but not for racing applications.
H