Limits of SCAT cast steel 9000 crank?

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Limits of SCAT cast steel 9000 crank?

Post  BBFTorino on November 17th 2018, 12:23 am

I have a SCAT cast steel 9000 crank it is a 4.5" stroke.
I am putting together a 557....14:1, solid roller cam, Edelbrock heads with major porting work (port walls are getting thin!!), D0VE-A block with Milodon splayed 4 bolt caps.
I expect that it will make 750-800 but I also want to spray it with a 250 shot. The general consensus is that the crank is the weak link in the parts combo.
What have these things handled before breaking/cracking, or completely exploding??
I can change direction and go with a forged unit now, before its all assembled....good idea or bad??

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Re: Limits of SCAT cast steel 9000 crank?

Post  rmcomprandy on November 17th 2018, 1:12 am

It should be fine until you spray it. At this output, I'd spend the extra for a forged unit.

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Re: Limits of SCAT cast steel 9000 crank?

Post  tfsbbf466 on November 17th 2018, 9:39 am

I exploded an eagle 4.14 cast crank in a mild pump gas 512 on a 73 jet. It lasted 2 years or so but it grenaded. Only thing left was the cam surprisingly and the heads were ok with only a few bent valves. Oiled down my favorite test spot lol

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Re: Limits of SCAT cast steel 9000 crank?

Post  rmcomprandy on November 17th 2018, 1:57 pm

tfsbbf466 wrote:I exploded an eagle 4.14 cast crank in a mild pump gas 512 on a 73 jet. It lasted 2 years or so but it grenaded. Only thing left was the cam surprisingly and the heads were ok with only a few bent valves. Oiled down my favorite test spot lol

Eagle cranks and Scat cranks are not near the same strength.

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Re: Limits of SCAT cast steel 9000 crank?

Post  tfsbbf466 on November 17th 2018, 6:28 pm

I didn’t realize that cast vs cast. My originally crank in the motor was a scat 4.15 cast but the converter ballooned and knocked the thrusts out of it. Replaced it with an eagle since it was cheaper and it already had no name rods. Paid the price in the end.

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Re: Limits of SCAT cast steel 9000 crank?

Post  Mark O'Neal on November 17th 2018, 10:52 pm

Saving money is expensive.....

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Re: Limits of SCAT cast steel 9000 crank?

Post  BBFTorino on November 17th 2018, 11:13 pm

Mark O'Neal wrote:Saving money is expensive.....

No kidding!! I already had the crank, and it was originally intended for to be used in a 557 with low compression, mild cam and more street friendly environment. It was to be a high torque, low RPM deal for a F-350 dually truck. But I want to get my Torino back on the track!!
The motor is still all apart right now, so upgrading to a forged crank at this point is going to happen!!

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Re: Limits of SCAT cast steel 9000 crank?

Post  dfree383 on November 18th 2018, 10:27 am

Mark O'Neal wrote:Saving money is expensive.....

X2 bite the bullet now.
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Re: Limits of SCAT cast steel 9000 crank?

Post  jasonf on November 18th 2018, 12:23 pm

dfree383 wrote:
Mark O'Neal wrote:Saving money is expensive.....

X2 bite the bullet now.


The people I work for "save" money like that every day....
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Re: Limits of SCAT cast steel 9000 crank?

Post  D. Sea on November 19th 2018, 9:56 am

Reminds me of the Flexy Flyer Cast 4.5 Crank that wiped out all of the bearings in Blakes 557 at one of our tech seminars. I believe it was making right at or near 800 HP when the oil pressure took a nose dive.

That was an Eagle 4.5" IIRC
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Re: Limits of SCAT cast steel 9000 crank?

Post  gt350hr on November 19th 2018, 2:35 pm

There is an actual reason why manufacturers make specific limits on their parts. Taking the parts beyond those limits can cause failure. A 4.500 stroke cast crank at 7,000 rpm is more likely to fail than the SAME crank ( or material) at a 4.300 (or less) stroke. Less stroke overlap , higher centrifugal forces , etc . will cause failure sooner. That is simple physics. Change material to a forging and the margin of safety increases dramatically. Change to a high end steel ( like Bryant uses for example) and crank life is extended even further. As Randy and others have already said saving money up front can be more expensive in the long run. Common sense must be exercised , not ignored.

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Re: Limits of SCAT cast steel 9000 crank?

Post  Mark O'Neal on November 19th 2018, 2:57 pm

The reason manufacturers make specific recommendations is because customers ask. So do lawyers. Horsepower is not the primary basis for selecting a part and the manufacturer has no idea what the end user is going to do with it.

A rod manufacturer has no idea if you're running a Moleculite piston.....or a brick.....or if you're running 6,000 or 12,000 rpm, for example.

Why did ARP recommend 20 torquings for a rod bolt's life? Because they had to pick a number. There is no specific number of torquings a bolt is good for.

And it's not like you guys listen anyway...... Very Happy

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Re: Limits of SCAT cast steel 9000 crank?

Post  BBFTorino on November 19th 2018, 11:46 pm

I will substitute this crank for a forged steel unit. And this cast crank will go back to being for a truck low RPM torque motor!! Cool

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Re: Limits of SCAT cast steel 9000 crank?

Post  gt350hr on November 20th 2018, 2:42 pm

Mark O'Neal wrote:The reason manufacturers make specific recommendations is because customers ask. So do lawyers. Horsepower is not the primary basis for selecting a part and the manufacturer has no idea what the end user is going to do with it.

A rod manufacturer has no idea if you're running a Moleculite piston.....or a brick.....or if you're running 6,000 or 12,000 rpm, for example.

Why did ARP recommend 20 torquings for a rod bolt's life? Because they had to pick a number. There is no specific number of torquings a bolt is good for.

And it's not like you guys listen anyway...... Very Happy

Really? I didn't realize manufacturers were so stupid.

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