Crankshafts

[Stangman]

Was looking on Scats website and thought it was odd that the lightweight cranks are cheaper than the regular cranks. I would think more machining on the lightweights. Obviously there out there but they don’t list a 4.375 crank. Is it a special order.

[My427stang]

Yes 4.375 is custom.

Lightweights are cast cranks, 9- part numbers, and the forged are 4- part numbers.

[blykins]

Where did you see the prices?  The steel Superlites are generally a lot more expensive.

Scat has went through some drastic price changes lately, maybe some venders havent caught up. 

[Stangman]

Right on website. Cranks, rods , rotating assemblies and more. Regular cranks like 1400 and lightweights 795. Big difference

[blykins]

Ross is correct.

In the SBF world, there is a lightweight and superlight.  Not in the FE world. 

So what they're calling a lightweight FE crank is actually a cast crank. 

Cast cranks are lighter than forged cranks, so technically they're correct, but it's kind of a misnomer because they have other crankshafts available with other families with "lightweight" and "superlight".

[Stangman]

If you go on the website they show a picture of both cranks and there is a big difference. You can see the difference easily. But being a cast and it definetly is thinner in some spots looks like if it was a high horsepower motor I guess it’s possible it could be a weak link.

[galaxiex]

Safe power limit for the Scat 4.25 stroke cast crank?

Would it be good to say, 650 HP?

[My427stang]

The common opinion is that in an FE, they can take a lot of power, some guys say well in excess of 700 hp

However, keep in mind, overall component balance (from balancer to clutch and everything in between), heavy/light parts choices, RPM, and even main design all matter.  A cast crank doesn't flex it breaks.  I tend to be a much more conservative.  it's a decent chunk of money to move up to forged, but how much for a broken block?

[Barry_R]

I have sold - and built - hundreds of FE engines with cast Scat cranks for over 20 years now. 
I have only had a few of them truly break. 
They were at or over the 700 HP level, or in continuous load applications - marine/road race.
Those guys - along with blower guys - simply require steel.  No option.
For everyone else it's insurance.

[blykins]

My rough rule of thumb is if you have an aftermarket block, go ahead and snag a steel crank.  Otherwise, in a lot of cases, the cast crank will live longer than a factory block will.