I bought a fairly beefy short block but it turns out the GM forged crank in it is no good. So now I'm scrambling to find a good yet inexpensive crank because I need to get this car running ASAP. The rest of my motor is

355ci 4-bolt
TRW forged flat tops
Childs & Albert forged 5.7" rods
ARP rods bolts and main studs

The motor will never see past 6500RPM but will hopefully be making about 450HP N/A and topping it off with 150-200 shot of nitrous now-and-then. Do you think the Eagle cast steel cranks are a good peice for the money? Do you think it'll safely handle the power I'm throwing at it? If not what would you recommend? I'm really low on cash and time here...

Thanks,
Chris

The eagle crank is a good choice for your situation IMO. I run one in my 5.7" rod 383 and have been beating on it for 2-1/2 years now with no crank related problems.

another vote for the eagle cast steel crank. i'm running one in my 406 currently, going on two seasons and no problem (knocking on wood), and it sees the high side of 6k occasionally. in fact my machinist buddy who reccomended it ran one in his 10 second blazer, w/ a 200 horse shot of nitrous, and never had any problems. supposedly scat's version is a decent piece as well.

Just bought a speacial cross drilled crank for my 427 and both the guy who recomended the shop and the shop owner said that the Eagle cranks have to be reground even when new. Not trying to vender bash but you might want to check into that before you put one in your motor. They said once they are turned they never had a problem with them but sometimes you get bad stuff from the factory, which is true with anything you buy.

I was looking into the SCAT cranks but its come to my attention from several sources that SCAT cast cranks are not to be used with Fluidampr balancers (and I just bought one brand new last month). Apparently the material density used by SCAT has some kind of resonant frequency that interacts with the fluidampr and can/will destroy the crank. I thought this was complete BS but after doing some searching on various websites it seems real....

I suppose I'm going with the Eagle cast steel unless I win the lottery or come across a better deal.

Thanks for the replies, keep 'em comin',
Chris

Take a look at this Scat Crank that was used with a fluiddamper... Will make you think twice before wasting a lot of money.

http://www.thirdgen.org/techbb2/showthread.php?s=&threadid=154125

Just out of curiosity guys, what do you think of the later model Chevy forged cranks? I have a new ZZ4 short block with the PM rods and the 1053 forged crank. I need to balance the assembly, thought about putting a new set of longer rods in it and a set of SRP's. Just wonder if it is worth it with the "stock" GM forged piece.

P.S. That was one ugly picture. Probably unfair to say from just looking at the picture, but that crank sure looked like a "cast" unit, the broken pieces are really "grainy." Yikes!

Mark

From what I have heard and read them GM Forge crank can handle about 500hp, so with that in mind I dont think that you will have any problem.
SRP is a very good pistons and the rod I would check into Eagle they have some very nice 6" rods in the $300.00 range on Ebay.
Hope this help or someone will chime in.
DTL504

Hmmmm... I keep reading that all the offshore cranks, rods, etc. are made in the same foundry and the rough castings are sent to the different companys for finishing. Scat, Cat, Eagle and whatever else. So if the Fludampr's react funny with Scat, which sounds fishy to me, it would react the same with the others.

Whatever crank you buy, have it measured. I personally measured 4 different Scat cast cranks and all were under tolerance and needed to be turned. My buddys Eagle forged was right on the money.

Lonnie

Well contrary to what i was told was going to be a mess of a crank, My clearances checked out perfect on my 4340 eagle 3.48 stroke. A little tight but still good. 2.2-2.5 on the mains except the thrust wich is in the 3's. and rods all checked out at 2.5 with my federal mogul comp. bearings. I have .0013-.0014 rod side clearance, and .005 crank end play. Like i said a little tight except on the thrust but it should be fine. Remember, you get what you pay for. If you want a crank that is blueprinted right down to the .0001, then call up callies or somone along those lines then be prepared to call your loan officer at the credit union. If you dont mind a hair of variation in your crank then go with the offshore piece, just check it out before you do anything to it. My guess is that chevrolet probably put alot of cranks in there motors that werent quite on spec but they all still ran. So why have your panties in a bunch over nothing. I know a guy that runs his crank/ rods etc, so loose most of you would say hes nuts but its been pounded on for 6 years now and has more oil pressure than he knows what to do with. So dont get cought up in the clearance game, as long as its not too tight, and isnt rediculously loose your probably fine. Just my opinion though.

The reason that FluidDampner's are not to be used on "CAST" SCAT cranks is due from the 9000 materials resonant frequency.

In the racing community, it has been advised by SCAT not to run a FluidDamper on their 'cast' crankshafts. The reason for this is that they have had failures from the specific harmonic of the materials in the crank and the dampner itself, (and something to do with its weight was also remarked on), tends to brake off the crank snout. This is a seperate problem from the 'honing' issue.

The material density used by the actual manufacturer (in China) has a certain resonant frequency. Appearently, one that doesnt work too well with the internal inertial weight of a FluidDamper. One would think it would be the same with all cast cranks, but there is just something about this one in peticular.

I have used SCAT cast cranks before, and have had no problem, after being told not to use a FluidDamper. I myself use ATI dampers exclusively. There product works better at higher RPM (in comparison to others) where most of my time is spent.

FYI - resonant frequency is dependent on the length and diameter of a material. The longer the piece of metal the lower the resonant frequency, the shorter the piece the higher the resonant frequency. Differenences in metalurgy will not change the resonant frequency, maybe increase or decrease the tendency to resonate, but not the frequency.

It seems to me that the main and rod bearings would prevent the crank from resonating. If there is a problem with the snout, I bet it is more a result of the dampener resonating (or not absorbing vibrations like its supposed to) and breaking the crank rather than the crank resonating. I've heard that fluid dampeners are not good for street motors (regardless of the crank mfr) for this reason --- wish I could remember where I read that . . .

:eek: :eek: :eek:

I have the fluidampr "streetdampr" version (non SFI) I'm now considering selling and running an ATI ...we'll see.

The only metalurgic difference that changes a component of frequency is density. This would result in a change in amplitude at a given frequency.

As I stated before There have been failures from the specific harmonic of the materials in the crank and the dampner itself . I wasnt trying to elude the fact of frequency being related to length and diameter more over than that of material and that it may be from not allowing the materials to resonate freely. Suppression can cause damage as well....

Fellows ,I have my engine finished and ya'll have got me scared.I have the scat cast crank from summit in the 383 with h-beam rods and KB hypereutectic pistons. I also have a streetdamper on the crank. I used the fluiddamper on a previous 383 and cheapo cast crank without any problems.I did speak to fluiddamper tech concerning balancing though,and was told to have the crank balanced with the original balancer and then put the fluiddamper on the engine. I think it's time to call scat.