Eagle crank need balancing?

[jpdeuce]

I am putting a 350 sbc together for a guy and bought one of Eagle's cast internal balance stock 3.48 stroke crank. I called Summit and they said even for a stock motor it would need balancing. So I went straight to the horse and called Eagle.
Eagle's tech guy said 95% of these cranks could go in the motor out of the box without a hitch but maybe 5% would experience a vibration if they were not fully balanced with the pistons and such.
Does anyone have experience with this crank? I was hoping someone on here has used this before.
BTW, it is a stock bottom end 2 bolt with Dart Pro One heads and a Comp Cams 253 @ .050 w/ .525 lift. This engine won't be driven real hard. The owner is easy on the pedal.

Any input is appreciated. Thanks.

[Lowend]

The Eagle guy is full of crap.... Without him knowing what rods and pistons you are using he can't make that assumption. As far as I'm concerned every crank/piston/rod combo needs to be balanced to work properly.
Yes you can go unbalanced, and it might be ok, but when spending $6K-$7K on an engine why screw around.

[camcojb]

The Eagle guy is full of crap.... Without him knowing what rods and pistons you are using he can't make that assumption. As far as I'm concerned every crank/piston/rod combo needs to be balanced to work properly.
Yes you can go unbalanced, and it might be ok, but when spending $6K-$7K on an engine why screw around.

Absolutely. Stupid thing to say on Eagle's part.

Jody

[70 Chevelle]

always balance

[6'9"Witha69]

Yes, ALWAYS BALANCE!! Weight differences in reciprocating parts is tremendous.

[Neil B]

If I'm not mistaken, Eagle publishes a 'target' bobweight for their cranks and they guarantee them to be +-2% of the target. For their SBC cast cranks, I think their target bobweight is 1870 grams. You can calculate the actual bobweight of your rotating assembly and see how close you are. With that said, I agree with everyone that you should have a machine shop balance the crank no matter what.

I just had my crank balanced and (using Oliver rods, JE pistons/pins/rings, Clevite rod bearings) my actual bobweight was 1910 grams.

[David Pozzi]

Any holes drilled in the crank counterweights?
That would indicate at least they balanced it to some unknown bob weight.
Without knowing the bob weight it's balanced to, it's a guess. Besides, the rods and pistons need to be balanced to each other first, then the crank is balanced to the rods and pistons including wrist pin, pin locks, ring, bearing and even surface oil weight.

A properly balanced engine runs so much smoother, - he'll be glad he did it.

[Neil B]

This shows the 'target' bobweight for Eagle cranks....

http://www.eaglerod.com/products/Chevy/small%20block/SBC%20cranks.html

I think it would be interesting to spin one and see how close it actually is to this bobweight.

[TonyHuntimer]

Every rotating assembly should be balanced. Eagle con get close...but close is not good enough.

Tony Huntimer