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Discussion Starter #1
Anybody hear of crankshafts breaking behind the harmonic balancer on these engines. I bought one awhile back and I really liked it( great torque and power) right up until the crank broke about 90 miles from home on a Sunday night(engine has about 12,000 miles on it). Water pump, alternator, and power steering pump is all that was running off the pulleys on the balancer. It looks like a crack started in the keyway and worked it's way around until it snapped, no warning, running fine, and then SNAP!!! I haven't pulled it apart yet or contacted the GM dealer I bought it from, I wanted some input from anyone who might know if this is a problem with this engine, or just bad luck on this particular engine. I don't want to put it back together with another GM crank if this is going to happen every 12,000 miles.
 

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That is really weird. I havent heard of cranks breaking very often, especially on street motors. I know guys running stock 400 cranks in 383s with up to a 175 shot of nitrous, running 10.80s and their cranks have held up. Are you running a gear drive? I have heard that those can send bad harmonics through your motor which can cause fatigue, but I wouldent think it could cause this severe of a problem so soon. If I were in your shoes, I would rebuild it with an Eagle cast or forged steel crank just to be safe.

Adam
 

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A couple things come to mind. What kind of damper/balancer? What kind of timing set? The multi key-way sets can cause the crank to break (according to Callies, they do not warranty cranks if you use a multi keyway set).

You could have just been unlucky and got a bad crank. How was the balancer installed? I know it is a GM engine but I don't know if it came complete are as a short or long block. Was the car or engine ever supported by the balancer of crank snout? Was the balancer loose at all (hard to tell now I am sure) if so it could have been beating on the keyway and caused a crack to start. I would return it since it should still be under warranty, correct?

I have seen some stock cast iron cranks take some MASSIVE abuse and not break. Do you have any pictures you can post?

Adam,
You are correct a gear drive "can" transmit (not cause) harmonics. This is usaually refered to when talking about valve train. On a high (7000+) RPM engine a gear drive can transmit harmonics to the cam/valve train and the engine will not want to rev like it should. On a lower rpm engine gear drives aren't a problem (love them or hate them). Timing chains tend to absorb the harmonics that is why some people swear they are better than gear drives. Even though in 99% of the cases it doesn't make much difference. This is also why some people like belt drives even more. All engines have harmonics, the gear drive doesn't cause them though. This is why there is a "harmonic" balancer/damper on most (if not all) factory engines.
 

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Discussion Starter #4
Thanks for the responses, the engine is as it came out of the crate, with original timimg chain and gears. The damper/balancer came already installed on the crank, all I did was install the pulleys and belts. The engine never rested on the damper/balancer or came into contact with anything, although the engine had broken loose from it's mounting on the crate before I pick it up at the dealer. I didn't notice any damage when I looked it over so I accepted it. Perhaps the damper/balancer did hit something when it shifted in the crate, but I would think a blow hard enough to damage the crank would have left some sort of external evidence.
 

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latheman,
WOW!! Sounds a little strange. I personally think you just got a bad crank. Either it was a bad casting or they damaged it before or during the install. I would not be afraid to run a GM cast crank in a mild performance engine. I have no experiance with the newer GM stuff so maybe the quality is not as good as it once was.

In any case if it is still under warranty I would take it back to where you bought it. I don't think they can really dispute the claim. It is not modified in any way. I wouldn't wait to long if I were in your shoes. Once rust etc.. start to form that will only give them and excuse.

Have you called them or anything? If so what did they say?

Sorry to hear about your misfortune

Royce
 

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Discussion Starter #6
The crank is advertised in the HT 383 specifications as being forged, and that makes this even more a mystery. The small block chevy has always been my favorite and I have never had anything but good luck with them (built my first 283 35 years ago in high school). I haven't contacted the GM dealer yet as I haven't had time to pull the engine yet. I would like to have the crank and balancer in hand when I contact the dealer. The engine is out of warranty time wise and probably just over the mileage too, but since this is so obviously a defective part, maybe I can talk them out of a new crank and balancer. That's why I posted here, to see if anyone else has heard of or experienced this problem with any other HT383's. I don't want to use another GM crank if this is a common problem.
 

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I understand. If you have a decent dealer he will probably take care of you. I didn't realize it was a forged crank. I will ask around but, this is the first time I have heard of this problem.

Royce
 
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