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70's Chevy 350; crankshaft choices?


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  #1  
Old 09-30-2017, 10:25:48 PM
Calan Calan is offline
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Default 70's Chevy 350; crankshaft choices?

Hello to all;
Time to replace my cracked block, and I need crankshaft advice.

This is for rock crawling and towing. Aiming for long life and dependability; excellent low end torque. Moderate compression; aiming to keep it under 5K RPM. Under 300 HP, for sure.

Seems I'm done to two choices for crankshaft replacement.

A. Track down an old OEM part and have it inspected and cleaned up by a competent machine shop.

B. Buy one a new one, on a budget. I could probably get away with cast, but have decided to go forged.

Option A means good quality American steel, but there will be no guarantees on the parts I scrounge, and I may have to buy 3 to get 1 good one.

Option B seems to involve being made in China, but they've been forging for longer than we have, and most everything is made in China these days.

All opinions welcome and appreciated.
Many thanks;
Alan
Central CA
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  #2  
Old 09-30-2017, 10:42:21 PM
Bob Shannon Bob Shannon is offline
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Default Re: 70's Chevy 350; crankshaft choices?

383!!! Sroke it!!!
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Old 09-30-2017, 11:10:47 PM
John Schwiebert John Schwiebert is offline
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Default Re: 70's Chevy 350; crankshaft choices?

When I worked in a shop we had good luck with 383 cranks!
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Old 09-30-2017, 11:16:06 PM
Calan Calan is offline
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Default Re: 70's Chevy 350; crankshaft choices?

Yeah funny!
More is usually better in my book, but in this case 350 is already an overpower.
The ol' '56 Willys Jeep is doing well to handle a stock 4BBL 350. Which it's done fine since '71.
So, 8.5:1 compression and a mild build 350 CI is plenty for this application.
Thanks!
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Old 10-01-2017, 12:31:59 AM
Greg Mosley Greg Mosley is offline
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Default Re: 70's Chevy 350; crankshaft choices?

Greetings Calan, Find a good used GM crank. Mag it, check it for straightness , rebolt and resize your stock rods, line hone the block. Install all undersize inserts in the rods and block and torque. Dial bore gauge them and grind the crank journals to achieve the proper clearances. A stock cast GM crank is plenty for your app. Don't waste your hard earned money. Enuf Said.
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Old 10-01-2017, 11:06:25 AM
slip knot slip knot is offline
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Default Re: 70's Chevy 350; crankshaft choices?

I agree, just about any crank will work for what you want. hit the scrap yards and find a decent looking crank, machine shop it and run it.
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Old 10-01-2017, 12:58:33 PM
Calan Calan is offline
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Default Re: 70's Chevy 350; crankshaft choices?

Info appreciated!

Any hints on avoiding junk?

If I can find a block and crank at a yard, I may get some sort of guarantee from them to refund / exchange if it turns out the parts aren't usable. I'll start there first.

But, if I find something interesting on Craigslist, I'd like to know what to watch out for. I'll look for obvious block cracks or excessive scoring / wear in the cylinders, and take a close look at the crank bearing journals, but any other tips on pre-purchase inspection will be helpful.

Many thanks;
Alan
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Old 10-01-2017, 03:54:05 PM
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OTTO-Sawyer OTTO-Sawyer is offline
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Default Re: 70's Chevy 350; crankshaft choices?

Personally, I'd just cruise the used car lots and find a cheap old beater car with a good running engine in it. (I've done that many times over the years)

Pull the engine and anything else worth keeping selling or trading and then scrap the car to recoup a good portion of the money.

Depending on the timing and scrap prices I've had some I bought for $200.00 (or less) pulled everything I wanted and scrapped what was left for more than I paid for it.

Throw in a good RV cam for low end torque & pulling power and you're done.

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Old 10-01-2017, 04:24:01 PM
CharlieB CharlieB is offline
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Default Re: 70's Chevy 350; crankshaft choices?

Hmmmm. You posted about the cracked block in another thread. Now you need a new crank, too? Sounds like you need a short block.
Rebuilding a junkyard engine is a gamble, as is buying off the Internet. You never know for sure what you've got until after you've put a lot of work into installing it in the vehicle. There are many engine shops in the Fresno area. I'd talk to some of them about a remanufactured (not rebuilt) short block. Lots of the Fresno shops sell Jasper remanufactured engines, which are good engines, but I'm not sure if Jasper will sell just a remanufactured short block.
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