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Old 06-20-2012, 11:13 AM
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What crank should I use?

First of all let me preface this by saying that I know very little about engine building. I have a 350 shortblock that I will be trading to a friend. I pulled It out of a toyota pickup about 6 years ago and I have been tripping over it ever since. My friend pulled the bearing caps off and he doesn't like the wear. The crank has pits in it. I can run my fingernail on the crank and it will catch. This crank is a factory forged unit that has been ground .020 My father has a cast iron crank that was bought new and has never been used. What would be the better choice? I am coming out ahead on this trade and I didn't want to get into this motor but I don't have a choice now if I want this trade to work. It is going into a pickup that regularly gets the bag beaten out of it in the woods. I was told to scuff up the forged crank with emory cloth and put it together with new bearings. Is that the best way to go?

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Old 06-20-2012, 11:18 AM
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Either way you will have to buy new bearings. If your worried about him breaking a cast crank dont give it a second thought. He cant get enough traction to hook hard enough to do that. Takes a good drag car with slicks that hooks hard to even be a issue.
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Old 06-20-2012, 11:21 AM
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No. Polishing won't "fix" a crank with enough wear to "hang" your fingernail. It should be ground. Bearings are readily available in .030" under, so that's not an issue. What IS an issue, is the surface hardening of a forged crank may or may not be "thick" enough for going .030 under. A trip to a metal treatment shop is called for to "measure".

A "new" cast crank? New from Chevy? Or an aftermarket unit? It should be balanced, but will "hold up" under most conditions. The imported castings aren't real "tough". Chevy nodular castings ARE pretty good, though.

Jim
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Old 06-20-2012, 11:44 AM
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The new crank is in an unopened box. It came to my dad with a bunch of other stuff when a parts store went out of business. He traded a vega for around half of their inventory. I can have it for $50. The cost of that crank and bearings will eat all of my cash. I know that i need bearings either way i go. I can't get the crank balanced or the other one turned without doing some fundraising. I never wanted to rebuild this motor in the first place. I didn't realize that the new crank would need to be balanced. I may just scuff the crank and hope it smoothes out. I know it's a bad idea but it's cheap. Is there any way to know if the new crank needs to be or doesn't need to be balanced?
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Old 06-20-2012, 03:25 PM
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If its a stock off the shelf oem crank or a reground factory crank you do not need to re-balance it to use it. It wont be out of balance enough to amount to squat. The steel crank sounds to me like it needs to be polished and checked for size. If that's all good put some new bearings on it and your set to go. A few divots in it wont hurt as long as its not rust. It'll just hold a little more oil at the bearing. Not a bad thing. The cast crank if new or a reground kit should be set to go. If any one thinks the factory balances each and every crank to each engine they are sadly mistaken. The are all balanced to a set number on the bob weights that will work on almost every stock engine. You will find a rebuild company take cranks to .030 under-size and never balance a crank and have maybe one out of 1000's that will have and issue with balance. And thats with a resize on the rods and over size pistons sometimes to the tune of .060 which adds weight to the bob weights.
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Old 06-20-2012, 04:43 PM
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I went up to my father's house and looked at the crank and it says refurb on the box and there are crank and rod bearings in the box so I bought it off of him and I will use that.
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Old 06-20-2012, 04:46 PM
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If thats the case its a reground and should be marked on the crank or box as to undersize on journals. Should also be marked on bearing boxes. Sounds like your set to go. Good luck.
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Old 06-20-2012, 06:46 PM
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Agreed. If a remanufactured (reground, put in a box with the appropriate bearings) crank, we refer to it as a "crank kit". It should be balanced "close enough" (as swvalvon said).

To someone like myself, "in the business", the word "new" has a different meaning than it has to others.

Jim
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Old 06-20-2012, 07:24 PM
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in my world of 3 minimum wage part time jobs new is also a relative term. if i didn't have it before and its not broken its new to me
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Old 06-21-2012, 08:05 AM
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Understood. "New to me" and "new" are completely different. One of my goals in posting on sites like this is to better educate the hobbyist on the correct terms and "nomenclature" so they can more accurately describe what they need or want to the parts or "service" guy. No "slight" intended.

Jim
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Old 06-21-2012, 10:52 AM
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congrats on the crank kit! $50 is a deal.

Only thing I would add is this. When horse-trading with friends; its almost always best to NOT do things like scuff the journals and hope it holds up. When it doesn't; which is usually the case when you do a job for a friend, he's gonna be pissed off. He's going to point his finger squarely at you; and expect you to fix it right. If your budget is THAT tight to consider those measures, you can't possibly afford to fix it the 2nd time.

I've seen several friendships depart over these kinds of things
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