Engine builders-Bent crank, replace or rebuild?
Thread Starter
Melting Slicks
Joined: Aug 2002
Posts: 3,333
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From: Central NJ/PA
Engine builders-Bent crank, replace or rebuild?
The crank in our 406 project is bent. The motor about 3k miles on it. Can we just install a new crank and bearings or do we have to take everything apart and have it balanced again? Thank for the help.
Jason
Jason
Thread Starter
Melting Slicks
Joined: Aug 2002
Posts: 3,333
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From: Central NJ/PA
Originally Posted by CFI-EFI
It will have to be rebalanced to the weights of YOUR components.
RACE ON!!!
RACE ON!!!
thanks alot,
Jason
Team Owner
Joined: Aug 2000
Posts: 40,156
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From: San Pedro CA
Originally Posted by cyclerage23
So can I jut pull 1 piston/rod an send it to the machine shop or do I have to pull the whole thing apart?
thanks alot,
Jason
thanks alot,
Jason
If you have a bent crank, what else was hurt?
Thread Starter
Melting Slicks
Joined: Aug 2002
Posts: 3,333
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From: Central NJ/PA
Originally Posted by bogus
I know this is a pain in the ***, but I would seriously consider re-rebuilding the entire motor.
If you have a bent crank, what else was hurt?
If you have a bent crank, what else was hurt?
Last edited by cyclerage23; Sep 12, 2004 at 06:56 PM.
Safety Car
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From: [Quote=WOEII] Is dried brown doodie powders man! [/Quote]
I am thinking along the same lines as Bogus. At the very least I would perform a complete disassembly and inspect every piston, the rods for straightness, both ends of the rods for out of round, and the piston pins. You have to ask yourself if you really want to do this twice because you know you'll be kicking yourself later in the event another part of the reciprocating assembly fails and you have to take it apart again.
Just my .02
Just my .02
Drifting
Joined: Aug 2001
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From: Holliston MA
Cruise-In VII Veteran
Originally Posted by cyclerage23
I dont think anything else is bad. The engine (ski_down_it old motor)already has Lunati rods/Wiesco pistons(stock crank). It still runs but you can see the end of it is not spinning true. It keeps throwing belts and breaking the accessories.
If the crank is bent, I'd be looking to have the block magnafluxed to make sure nothing has cracked. I'd then be looking to try to see if the damage is shipping related or run related. If it's run related, it's time to give everything a real close once over.
You'll need to give the machine shop your balancer, flex plate / flywheel, upper and lower rod bearing halfs, rings, piston, and pin for a single cylinder for them to come up with a bob weight to balance the new crank. It wouldn't hurt to double check the weights of all the pistons and rods.
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I would think that align boring or at least checking would be in order too, if it is truly bent.
Le Mans Master
Joined: Feb 2002
Posts: 5,970
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From: San Marcos Texas
with SloRvette, make sure its not the balancer or pulley that is bent. It takes alot to bend a steel crank. It usually takes NOS, a supercharger backfire or somthing like a broken rod through the side of the block. My crank is a forged Callies that I bought from a friend of mine out of his dragster. He had aluminium rods and one broke. And it put a hole the size of a grape fruit through the side of the block. But the crank is still straight as an arrow....
Thread Starter
Melting Slicks
Joined: Aug 2002
Posts: 3,333
Likes: 1
From: Central NJ/PA
crank
Originally Posted by chriswtx
with SloRvette, make sure its not the balancer or pulley that is bent. It takes alot to bend a steel crank. It usually takes NOS, a supercharger backfire or somthing like a broken rod through the side of the block. My crank is a forged Callies that I bought from a friend of mine out of his dragster. He had aluminium rods and one broke. And it put a hole the size of a grape fruit through the side of the block. But the crank is still straight as an arrow....
Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
1/8th 
seems like that thing would be knocking like he77! plus I'd also think you'd be spewing oil all over from the front of the engine. The stock cranks from GM have been taking alot of punishment over the years and typically hold up very well. Sorry about your problem-but please let us know-at least I'm very curious to the outcome.
seems like that thing would be knocking like he77! plus I'd also think you'd be spewing oil all over from the front of the engine. The stock cranks from GM have been taking alot of punishment over the years and typically hold up very well. Sorry about your problem-but please let us know-at least I'm very curious to the outcome.
Thread Starter
Melting Slicks
Joined: Aug 2002
Posts: 3,333
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From: Central NJ/PA
Originally Posted by rick lambert
1/8th seems like that thing would be knocking like he77! plus I'd also think you'd be spewing oil all over from the front of the engine. The stock cranks from GM have been taking alot of punishment over the years and typically hold up very well. Sorry about your problem-but please let us know-at least I'm very curious to the outcome.
seems like that thing would be knocking like he77! plus I'd also think you'd be spewing oil all over from the front of the engine. The stock cranks from GM have been taking alot of punishment over the years and typically hold up very well. Sorry about your problem-but please let us know-at least I'm very curious to the outcome.Last edited by cyclerage23; Sep 13, 2004 at 12:20 PM.
Le Mans Master
Joined: Feb 2000
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From: Kempner Texas
Originally Posted by cyclerage23
I'm guessing the bend would be about 1/16 in direction, but would go both ways when spinning. Thanks for all the help!
Jake
Thread Starter
Melting Slicks
Joined: Aug 2002
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From: Central NJ/PA
Originally Posted by SloRvette
Have you really run the motor since you bought it, or is this damage that was there that you're just figuring out now ?
