What RPM/HP is a Scat 9000 good for? Goal = 400hp and ~5800 shifting. No power adder. Car will be driven daily for 5 years or so. Given that goal, any reason to go forged?

Another question: What is the difference in how cranks are made, i.e. Forged and Cast. I know the benefits of forged but how are they made differently?

-Corey

 

I have never run one, but if you accept Scat's word at face value, that 9000 crank is about the same strength as a factory stock GM forging, so presumably it should easily handle the power and RPM levels you mentioned.

I do question why you wouldn't step up to an entry level performance forging though. The additional cost of the part is probably worth it.


I was watching a discussion on another board where the point was made that it's probably a good idea to build the bottom end for the engine you fantasize about, not the one you are building.

Why?

Because then when (if?) you decide to upgrade to better heads or use a power adder, your block is already ready.

The point was made, and I agree, that we pay too much attention to the top end of engines these days, and not enough to the bottom end.

 

I'm on a 16 year olds budget so I was trying to stay cheap. I'm leaning towards a Calies Dragonslayer, but just wanted to see what everyone's opinions on the 9000 were before I order the DS. I geuss no one can complain about the Dragonslayer though

Another question, when building a 383: H vs I beam. Scat's website says their 4340 Forged H-beam is stroker clearanced. Aren't all H-Beams stroker clearanced, or at least less clearancing required when compared to an I Beam?

The block I'm using is a 136k stock casting. Came from a 1990 GTA L98. What all should I have done at the machine shop for prep work? Bore (.030"), Hone, Deck?

As far as the infamous 6.0" vs 5.7" debate...from what I've gathered, a 5.7" rod will be better for thousands of street miles correct? An all out race motor would be where you want the longer rod? Am I right?

 

400/5800 is no sweat for a Scat 9000. I'm hoping you mean a 383 and you may need to twist it a little more to get 400 rwhp.

9000 is a cast ductile iron crank. The molten iron is poured into a mold and cooled. It is then heat treated to give it the ductile properties. That means it will act more like steel and stretch or elongate before it breaks. It's a lot less brittle than grey cast iron used for blocks and sometimes heads, etc.

Forged steel (not iron) is made from a slug of steel (60-65 lbs. or so), which can be a number of alloys, but 4340, a steel containing nickel, chrome and molybdenum ("chrome-moly") is preferred. The slug is heated (red) and pounded into the rough shape of a crankshaft. The steel has a grain structure, and the hot forging stretches the grains as the metal is shaped. This can help the strength.

Both cast and forged cranks are machined and finish ground the same.

The basic cost difference is the much lower cost of producing a casting and there is often less machining required of the casting because it can be cast closer to the finished shape than can a forging. Additionally the 9000 is produced in China (like it or not). I have been impressed with both the quality of the 9000 and the very reasonable cost. IMO, it's better than stock ductile iron cranks.

Good cast cranks can be superior to mediocre low-alloy forgings, especially if the forgings are used. Both have their place in engines. Of course, so do "billet" cranks, which are machined from a 350 lb. chunk of alloy steel. These can cost 10 times as much as a 9000.

If you really aren't going to be spraying or going to multi-thousand dollar aftermarket heads, stronger driveline parts, etc. and plan to street drive it with 400rw, IMO, going to a forged crank isn't necessary for you. I'd consider hypereutectic (cast) pistons, and a reasonable cost I-beam rod. These wil be more than enough. Any money you save over forged crank, pistons and high-buck rods can be spent on good head work and a valvetrain which meets your power/driveability/durability goals.

Get in touch with an engine designer/builder for advice on the specific bits.

My $.02.

 

As usual, if you listen to Jon's sage advice you can't go wrong. You certainly don't need a high-end crank for what you have in mind. There are a lot of 400rwhp cars out there with cast cranks. Good machine work and assembly are going to be your key to 5 years of trouble free engine performance, along with proper operation and maintainence.

H v. I beam is an endless and pointless debate. The differences between a 6" and a 5.7" rod are also fairly trivial in this context. Though I guess I'd go for 6" for an NA buildup like you are planning. But if I had a good set of 5.7" rods sitting around, I'd use them. Your best bet, if you are getting everything new, is to buy a complete balanced rotating assembly. Save some $$$ and everything will work together. I know of more than one person who got the parts individiually and ended up with a major mismatch like crank and rods with different journal sizes

Take the block to a good machine shop and let them inspect it. They will tell you what needs to be done. To a point, it will depend on what you plan to do as well as the condition of the block. For example, if you are getting new main caps it will need to be align honed. It may already have been bored, etc.

Rich Krause

 

Corey,

The 9000 is more crank that you will need by a ton. Spend the $500 difference between the Dragonslayer and the 9000 on your heads. If you do choose to upgrade later on then you will still be o.k. with that crankshaft in the bottom of your motor.

Forged cranks are mostly needed for high RPM and high HP stress loads or both.

The Scat 9000 can easily handle a 600hp street car motor without any problems. You can see them living a nice long life on blown and 200hp shot motors all the time.

I have to disagree with the fact that guys don't spend enough attention on their bottom ends and spend too much on the top end. If that was the case then we would regularly have 500rwhp 383 LT1's all day long. Look around here, there are a ton of guys with over kill bottom ends and not enough heads and valvetrain for the bottom end.

True it's not bad to over do the bottom end, but street car stuff almost never even comes close to over doing the bottom end.

Bret

 

600hp?! Sweet! And they're only $200, so even in a couple years if I want to go forged I'm really not out that badly. Geuss the 383 can go together a whole lot sooner

Are cast rods OK too? I know GM Powdered Metal rods are awesome but what about others, such as Scat's I/H Beams?

I'm definitely getting forged pistons, I might do a 75 shot.

Also, does "neutral balance" mean internally balanced (when talking about the crank)?

 

600hp if you keep the RPM down.

Don't go with stock rods. At least put some Scat dowel cap I beams with that. They are $280 a set and are well worth it.

Neutral Balance esentially means internally balanced. You correct the flywheel to neutral balanced so if you ever break anything you can still have everything zero gram balanced even with a different flywheel.

Bret

 

Bret, I agree on the overkill bottom ends here. I've seen more than enough "all billet, forged bottom end 383"s with stock heads here. I do like the SCAT 9000 stuff. My friend had one in his 331 stang and it took 500 rwhp and almost 600 rwtq with no problems. Then again, I know a guy with more than 600 rwhp on a stock 5.0 crank, so....there could be some luck too.


As far as rods go, for less than 600 hp, I would figure the I beams would be good, but to what power level ARE they good to. I plan to do a 383 in a while, and it seems that every budget set of rods have around a 475hp rating. I'd like to see around 450 rwhp, even 475 if possible. I know the focus has to be the heads and valvetrain, but, I don't want to go overboard or too cheap on the bottom end. I've heard alot of talk about keeping the bobweight light, and figured an I beam rod would be lighter than a h by good measure. Do you have any recommendations for a piston/rod/pin combo that would come in aroung 1500 grams, or close to it?

As far as choosing that number, I must admit that I'm doing a bit of parroting, as that's what I've heard would be good. Your opinions on it would be great. Thanks!

 

Brain,

Low Bobweight helps a few things....

First off the less mass that has to be started and stopped in a motor takes less power to accelerate. In fast acceleration dyno tests you will see the advantages of this more than on slow ones. So lighter is better, as long as it is strong enough, and in it's own right, light makes HP.

Another good benefit of it is that there are less forces acting on the crankshaft trying to break or bend it. Same thing with a lighter piston and pin combo, a light piston and pin combo will stress the connecting rod less.

As for the connecting rod side of things.....

There are two loads on a rod Compressive (from the combustion process) and Tensile loads (which are from RPM)

Compressive loads can be higher, but the beam of the rod takes that, while the Tensile loads are from RPM. While tensile loads are not as strong they are what will break the rods over time due to fatigue stress.

So that's the main reason why good strong rob bolts are so important.

With that some companies will rate connecting rods in both HP and RPM. I look more at the RPM rating, because if you are going to exceed a rods rated HP then it's not going to be by a ton and the RPM rating is usually very high for circle track and drag race motors.

As for recomendations e-mail me on that.

Bret

 

I just more or less let my SCAT 9000 that was used go for like $150
or less. If you are only going to be spinning it to 5800.. You won't
have the slightest problem with this crank. I was under the impression
by reading ads (might or might not be true) that it was around 20-30%
stronger than the stock crank. There are a ton of stock cranks out
there with large cams being shifted at 6500rpm+, as well as tons
of stock pistons taking 100-150 shots setup properly running for
multiple years.

And just for encouragement. I'm running a 355 in my 1984 z28,
it was built with h beam rods, speedpro forged pistons, and a new
stock gm crank. I bought the car with about 10k miles on the motor.
The car had been shifted at 6000-6300rpm. I then installed a larger
cam and did some upgrades to the car. Since then, I have been
shifting at 6600-6800. The car has made several 100-200mile trips,
and has been driven right around another 10k miles since purchased.
Thats 20k miles+ of abuse. I plan to add some AFRS and a larger
cam and step up to the 7k rpm band. I'll just keep driving it til it
blows up and put something else in it If a stock GM cast crank can
handle 20k miles of 6000-6800 rpm abuse and still run like a charm.
I'm sure the scat can handle your level of abuse for a long long time

Good Luck,

 

scats 9000 are rated at 600hp at 7500rpms

 

I guess im on the other side of the road when it comes to high dollar low ends and low buck top ends.

My cast cranked,GM rodded,hyper slugged 355 solid roller turns 7000 rpm every pass.2 Summers and still kicking. I know its a bomb waiting to go off but its holding its own so far. Pushes my 3400 pounder camaro to 11.9X@115 and 11.0s@124 on a small plate. Would go quicker with more converter.

Im just a shade tree hack but a GM crank,cheaper I beams and KB hypers(balanced,good fasteners and built CORRECTLY) will live a happy life at 400 rwhp.

 

i bought an internally balanced scat stroker package (scat 9000 crank, 6" scat h-beams and srp forged pistons) with rings and bearings for a little over $1000 on a group purchase. this engine will see ~6400~ rpm on a regular basis and i have no concerns about the quality of parts in the bottom end.

there are always vendors out there doing gp's and you can usually get a screaming deal if you're willing to wait.

 

I just want to throw back in there...

Yes, there are many overbuilt bottom ends out there.


However, entry level forged cranks are not terribly expensive and there's no easier time to do it than during a rebuild.

Jegs has some Eagle 4340 forged cranks for $675.
I'd imagine that Scat's entry level forging is in the same neighborhood.


Now, there is no denying that this is almost $500 more. And there's no doubt that the 9000 will work for you.


However, before you decide to get it, you should consider very carefully what your future plans are.

There will never be a CHEAPER time to get a forging than right now.