03-27-2021, 02:58 AM | #1 |
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Join Date: Jul 2015
Location: 2nd left past the stump on a dirt road.
Posts: 2,629
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SBC Crank Questions
So I will be blunt. I need a new engine. 50 years it made it. Now I have problems.
Engine missing, ignition, coil, heads heads, carb everything will have to be gone through. When I did the top end rebuild 10 years ago everything in the block was stamped .010. The pistons, and crank specifically. Someone at a "reputable shop" informed me that once the crank has been turned once at that spec and then driven it is toast. What do you think of this statement? Can a SBC 350 original cast crank stand up to more turning and .020 or more tolerance??? Original 390K motor, 2 top end rebuilds, 1 bottom end with all reciepts. I want to go new, but you know how it goes..... |
03-27-2021, 03:57 AM | #2 |
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Join Date: Jan 2001
Location: Orem, Utah
Posts: 7,798
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Re: SBC Crank Questions
I've seen them turned as far as 30 thousandths. That probably wouldn't keep me from building a motor I wanted to build, but... it kind of sounds like you're looking for a reason to go newer. I just built an L31 Vortec for my Blazer and I'm really happy with it. You get a 1-piece rear main seal, roller cam, and Vortec heads (plus about 100 horses) in the deal. If you go that way, you'll need to change the flexplate or flywheel, get a new intake (different bolt pattern) and depending on the block, you might need an electric fuel pump.
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03-27-2021, 10:01 AM | #3 |
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Join Date: Nov 2007
Location: Gardnerville NV
Posts: 220
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Re: SBC Crank Questions
I agree with Truckster
My son an I swapped an L31 engine in his 86k20 due to broken flexplate an to many leaks. There is a learning curve with them, mostly due to only playing with First gen 350'S. But this site I full of knowledgeable folks. His truck has more pep as well as snappier. memo
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03-27-2021, 11:19 AM | #4 |
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Join Date: Jul 2012
Location: Whitehorse yukon
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Re: SBC Crank Questions
If your building high hp race engine then yes
And untill you tear apart your current build you wont fully know yhe crank specs Is your oil pressure still good ? Current crank can probably just need a polish Alternatively you can just replace the crank I have built 300 hp engine with a 20 20 crank no issues Are you wanting a roller cam best solution is go with a 86 up block An l31 block is the 86 up fitted with roller cam and vortec heads Good cheap canadates i found are full size vans ran l31 until 2002 can be found cheap with clamed failed head gaskets as the factory gm intake gaskets always leak I picked one up free that way po was determined blown head gaskets towed it home fired it up drove into the shop 40 psi oil pressure shut off Pop the hood watch the coolant run down the front of the block check oil yes it is milky i know he did not wash the bearings out that would affect the oil pressure on a stock motor |
03-28-2021, 02:53 PM | #5 | ||
"I ain't nobody, dork."
Join Date: Sep 2007
Location: Whidbey Island, Washington
Posts: 8,921
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Re: SBC Crank Questions
SBC 350 cranks are a dime a dozen. A decent machine shop should have drop ins already turned and ready to drop in for about a hundred bucks.
Gary
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