SBC Crank Questions

[toolboxchev]

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.....

[truckster]

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.

[memo43]

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

[gmc684x4]

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

[GASoline71]

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