Crankshaft Failure

[hivewax]

Crankshaft - Wikipedia, the free encyclopedia

what can i look for to what of caused crankshaft failure?

maybe from engine balance... while ago, the distributor gear teeth was chipped. it was replaced with a billet steel. the old gear was a softer alloy. can bad engine harmonics cause this?

a machine shop stroked the original 289 to 347 using a Eagle stroke kit. after the rebuild, the car has seen ~9000 miles. the engine is still under warranty, but they want me to pay for a new forged Eagle crank and labor because from what they said the part failed due to driver's abuse or an manufacturer defect and not from the engine assembly process.

here's more discussion...
http://forums.vintage-mustang.com/showtopic.php?tid/1508530/

 

[iapexl8r]

What was the horsepower out put? did you dyno. the cast crank should be good up to 400 rwhp depending on the usage. Throw slicks at and 5,000 rpm launches or run it at a sustained rpm over 6200 you are asking for trouble in the 350 range especially with a cast crank from china. Its much like the metric bolts from china a grade 8 (china) bolt is approximatly half of what the usa standard is. When you get a crank from china (or any other part) you just dont know what you are going to get. From the looks of it there was a casting flaw. If it were me I would get the broken crank and have some one from another good machinge shop take a look at it, if he is experienced he can tell you what caused it. Or you can have a metalurgist take a look at it. Then get eagle involved they may kick down a new one. They should want to see there broken parts so they can make improvements.


Chris

 

[blown65]

I would read the warranty carefully. If its just a blanket 1 yr 12,000 miles parts/labor with no disclosure on how its used or parts exclusion, then they can go pound sand. Pay the difference between that cast crank and the forged and be done with it. They cant go change the rules of a warranty to suit them. Are they saying they sent a motor out with a crank that wasn't sufficient for the build, yet now won't warranty it? I'm sure there is more to the whole story than whats posted here.

I agree with this poster.

Harmonics will do that to a crank, is it balanced properly? That could have twisted some of the mains also, it may need to be line bored. The only thing I would pay for is the price difference between a cast and forged crank. It sounds like his warranty doesn’t mean crap. Maybe turn him into the BBB if they don’t make good on this. Hell, why even have someone build it if they won’t stand good for it.
Greg

Why people put cast cranks in is beyond me, the forged ones aren't that much more money.

 

[10secgoal]

How much hp ? That casting has to be stronger than an original Ford. I had very good luck with my cast, stock crank. You need to talk to Eagle, not the builder about getting you a new crank.
That is the problem with engine building. He is right, it does look like it wasn't his fault.....BUT, he did give you a warranty on parts and labor. So now he owes you. If you can't get it out of him, there are avenues you can take that will help.

I also have a 347 crank here if you can't figure something out. It was in a motor with a broken piston. Pay for the mag and to have it checked, and if it's OK, you can have it.

 

[hivewax]

never did a dyno. the builders are saying the crank failure is not due to their balancing and assembly of the motor, so it's not under their warranty. is this definition of warranty used by all builders??

 

[GNGREN]

I think you need to play hard ball with them. They aren't your friend. They supplied the parts, and put it together. There warranty is for parts and labor. If it is a bad crank it is on them. As they supplied the part, they need to fight with Eagle. How can they prove it wasn't from their assembly or a balance problem. If I tried to tell one of my electrical customers that I am not replacing a switch, plug, breaker or fixture that goes bad during our warranty I would be out of work from the bad PR. Now if they supply there own material it is on them. Not my problem it went bad. I know I have had people threaten me before and generally it is way less expensive to just do what they want than fight them. Tell them you are going to get your lawyer to look at the warranty, don't let them walk over you. If you don't put up a fight they can say whatever they want about their warranty.


Also you really need to look at the warranty they gave you. Read and see if it excludes anything specifically. They can't change the warranty to suit them just because they have a problem that needs fixed.