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chevytech 05-11-2004 07:36 PM

Balanced Rotating Assembly
Wow, this is a cool site. I just bought an eagle street strip rotating assembly from a friend. He bought it about six months ago and never took it out of the box. He went with a big block instead. I bought it real cheap from him for my 383 build-up. The assembly is already balanced externally and comes with everything. I brought the rotating assembly into my machine shop along with my block to have some work done to it. They called me back a few days later and told me my new crank was garbage. I went in and took a look at it and talked to them. They showed me the spot where they drill out holes to take weight out on the crank to balance it. Below that, right beside the journal area they drilled another hole to take more weight out. He said by drilling down there instead of grinding, it is about 80% more likely to crack and break. Also, the rod journals have cross lines in them and he said that will cut the motors life in half. Is all this true or are they blowing smoke up my ***? Someone please help me. Thank you.

Mat Boardway 05-11-2004 08:48 PM

I'm no expert by any means. Though I just got done building my 383 and I bought a eagle crank and went to internal balance it and it would of cost me 200 or so worth Mallory metal to get it right and a ton of holes in it. I called eagles tech line and complained to them about the internal balanced crank I bought. The more or less told me that I would have to run some TRW forged pistions instead of my Wiesco's. So I instead external balanced the assembly with no real problems.

It sounds like your machine shop tried to internal balance instead of external balance your assembly.


machine shop tom 05-12-2004 09:25 AM

For what one pays for a crank like an aftermarket cast steel crank, they are a really good deal. Having said that, one must also realize that, fairly often, they may need to be turned to get them right. Even with the cost of having one turned, they are still a good deal. After all, it isn't a $1500 Callies piece. As far as where the balance holes are drilled, I wouldn't sweat that. I would find another shop, and have the rod journals turned to get rid of the questionable marks.

Eagle now has internally balanced cast steel 383 cranks. You must remember also that the Eagle cranks have a "target bobweight" built into them. The proper components will net you the correct bobweight to prevent the need for heavy metal. A competent shop that balances should be able to help you determine what your theoretical bobweight would be with your choice of components.


DTL504 05-12-2004 05:08 PM

Thats why I stay away from Eage Cranks, too many problems. I just had my Rotating Assembly consisting of: Scat 4340 Crank, Wiseco Pistons, Eagle H-Beam Rods, Pioneer Damper and Flexplate. All Internal Ballance and she did not need any mallory. Cost $213.00. I have seen too many Eagle Cranks on Ebay that were out of round on the journals and had to be turned 10/10 brank new cranks. I think thats just poor Quailty Control on who ever overseas that department.

machine shop tom 05-12-2004 07:48 PM

What has been said of Eagle cranks can also be said about Scat, Ohio, Summit brand, and others. The point is, it's best to check the stuff out. Also, I would stay away from Ebay "deals". I buy through reputable suppliers. If I have a problem with a part, THEY have a problem with the part.


LilSmoke 05-12-2004 07:54 PM

I have a 4340 eagle crank in a 555 thats been in for over 2 seasons. It took no extra for the balance and was spot on out of the box. this is #2 as the 540 also has one and have never seen any prob with either.Am also using the .250 long 3d rods with the L-19 bolts and work great.

Are the probs with the cast cranks,or?

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