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Old 12-16-2009, 09:17 PM
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Scat 9000 crank limits

I am building a cheap budget chevy 400. I was thinking of useing a Scat Stroker lightweight 9000 crankshaft and a set of 5140 I-beam rods (6.00") for competition products. My question is what is the Max Rpm and Comp ratio i can go with.

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Old 12-16-2009, 11:11 PM
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I have used the Scat 9000 in 3.75" stroke in three 383's and a 406, all were 11-1 compression and run to 7500 rpm without failure. Two of the 383's are 4+ years old. Have also used the 3.48" stroke Scat 9000 in two 350's, one at 13-1 and 8200 rpm, the other 11-1 and 7500, no failures, so I guess I don't know the limit yet. These are street/strip engines in 10 and 11 second cars, one of the 383's has been hit with a couple years worth of 175 hp nitrous hits. The 8200 rpm 350 is using the same rods you listed from Competition
Products. All of these cranks and King Bearings came from there too.

Take these results with a grain of salt if you are searching for circle track limits with these cranks, it is a harsher enviroment.

Light pistons mean a lot, all of these engines had pistons under 510 grams each.
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Old 12-17-2009, 06:10 AM
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crank

Eric gave you excellent advice.

I have run these cranks in many 383 and 4 or 5 406's. Never had any issues with them. Pay attention to what Eric said about piston weight. Get the lightest pistons that you can for your intended usage.

Can't comment on rods, I am not willing to push that envelope as hard. I use H beams in most of my higher RPM builds.


Keith
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Old 12-17-2009, 08:57 PM
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Thanks guys. I was planing on 12.9to1 and running Rate around 7000 Rpm.
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Old 12-17-2009, 10:23 PM
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Great cranks building a 406 11.1 solid roller motor the same combination 9000 with 6" 5140 scat i beams with mahle forged flat tops had mine internally balanced, good investment. havent heard anything bad about these cranks been known to take a beating and hold up well if i was building an all out drag car id have a forged but dont think you'll find its limits on a street/race car.heres a few pics of mine going together,

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Old 10-10-2013, 11:49 PM
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Limit on pump gas compression? What are you going for, I mean you could do 12.5 : 1 if you want a cam overlapped and run mild on timing advance...

Pushing compression limits requires forethought and money. Cold air intake. Run a tad rich or cool fuel with co2 - stuff like that.

Really, the deciding factor is how much driveability you want, you narrow torque range with huge overlap. And torque moves you, not hp.
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Old 10-11-2013, 12:10 AM
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race engines have a 30/30 guarantee
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Old 10-11-2013, 05:39 AM
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Gotta consider when talking about internal balance $200 to spin it + Mallory could add another $350 to $400 to the price of the crank.Could be you save on the purchase,but end up paying to complete it.
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Old 10-11-2013, 06:51 AM
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Quote:
Originally Posted by Jkwylde78 View Post
Limit on pump gas compression? What are you going for, I mean you could do 12.5 : 1 if you want a cam overlapped and run mild on timing advance...

Pushing compression limits requires forethought and money. Cold air intake. Run a tad rich or cool fuel with co2 - stuff like that.

Really, the deciding factor is how much driveability you want, you narrow torque range with huge overlap. And torque moves you, not hp.
Well that's all a bunch of silly nonsense.
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Old 10-11-2013, 03:35 PM
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Quote:
Originally Posted by Hammerchvy View Post
I am building a cheap budget chevy 400. I was thinking of useing a Scat Stroker lightweight 9000 crankshaft and a set of 5140 I-beam rods (6.00") for competition products. My question is what is the Max Rpm and Comp ratio i can go with.
These have proven to be very durable, but when you say 7000 RPM that's getting to be a lot as structural loads go up at extreme rates with RPM and once you start above 6000 you've got to pay careful attention to the details. You're also getting to the place where I think 5140 is being pushed pretty hard, I'd rather see 4340 for the rod, I'm more concerned about the rods than the cast nodular crank as the latter with good balance will hang in there pretty well. Since you're looking at Competition Products I'll link this as good rod for this application Scat, Chev SB, 4340 Forged I-Beam Rods, 6.000", Bushed - Competition Products . It's a bit heavy but at 7000 RPM I think you're well advised to keep the balance internal and spring for a very good damper. If you go for an external balance then the damper becomes that much more important. From a cost stand point it's probably a push with internal balance and moderatly expensive damper to externally balanced with a more expensive damper. This gets back into the crank material where cast being stiffer and more brittle than forged requires a very good damper in a high output high revving engine because unresolved forces in the crank will cause a cast crank to break where it causes a forging to wander off center which carve's out the number 1 main bearing often you at least get some warning from the bearing noise so you can go on risk with a less costly damper. If either go to failure both are major disasters you're just chosing which one to have. If you intend to race this an engine turning 7000 RPM will be required to have an explosion proof SFI approved damper. So be sure to budget this.

Bogie
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Old 10-11-2013, 04:08 PM
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Quote:
Originally Posted by oldbogie View Post
If you intend to race this an engine turning 7000 RPM will be required to have an explosion proof SFI approved damper. So be sure to budget this. Bogie
NHRA requires an SFI 18.1 damper at 10.99 (1/4 mile), but Bogie is correct. If you intend to spin the motor past what the OEM damper was designed for, then an aftermarket damper is called for.
For what it's worth, in my past 20 years of teching at Firebird and other dragstrips, I have seen more ATI units than any other brand.
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Old 10-12-2013, 12:52 AM
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Ive had a GM balancer slip the ring to the point it was lucky that it did not come unglued.Changed between rounds at S.I.R.
I wont use a stock balancer again
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Old 10-12-2013, 10:42 AM
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Those Ratter's I don't like.Fluidampr used to be really good(tight and hard to get on),but I have been told recently they let the quality slip.We had had them on a bunch of our 9.90 cars over the yrs.But then again those where the earlier built ones.

The Original Fluidampr
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