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  #16 (permalink)  
Old 03-02-2003, 03:09 PM
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If it is a 400 crank... you better put external balnce on it .. every 383 or 400 is identified by the balancer..i will

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  #17 (permalink)  
Old 03-02-2003, 03:32 PM
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Without trying to sound like I'm trying to start an argument Deuce but what you have done with your 283 is make the crank lighter, thats all...and made the counterweight inertial masses equivalent for that particular bobweight.

We talk about balance like there are not other forces that affect the balance of the engine, combustion pressure, quench clearance, piston diameter, cylinder wall friction I could go on and on. How is your bobweight determined? By using half the rod weight plus the pin right? So essentially you are treating the rod as two separate pieces, not really very realistic since every one knows rods are one piece. What about windage and the half pound of rotating oil mass attached to the crank at all times. All these are factors that affect balance that are not accounted for in a simple bobweight calculation.

In real life of course this is all we can do with the mechanical components to effect any change, but really when you do flywheel calculations and bobweight calc you are assuming a great many things that have no basis in reality. The original engineers who designed your engine took a great many things into account when they designed the original crank throws and much of the knowledge and rules of thumb were developed in the rail era, funny many things have not changed all that much.

Did you notice that the amount of out of balance for your original spin was 200 pds at 6000 rpm? Funny but that just about coincides with combustion chamber pressure during compression and the max safe rpm the motor was designed for?

Have you ever read Smokey Yunicks book Deuce?
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Old 03-02-2003, 03:46 PM
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[quote]Originally posted by 4 Jaw Chuck:
<strong> What about windage and the half pound of rotating oil mass attached to the crank at all times. All these are factors that affect balance that are not accounted for in a simple bobweight calculation.</strong><hr></blockquote>


IF you will go back and look at the Bobweight card...it has 3 grams added for oil on the pistons.

I cannot change your mind and I am satisfied with what I have said. I have changed flywheels (153 to 168) after balancing a assembly and the balance changed (still in the balancer) SO let's just agree to disagree.


Have a nice day !

[ March 02, 2003: Message edited by: Deuce Roadster ]</p>
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Old 03-02-2003, 07:40 PM
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[quote]Originally posted by Deuce Roadster:
<strong>
I have changed flywheels (153 to 168) after balancing a assembly and the balance changed (still in the balancer) SO let's just agree to disagree.
</strong><hr></blockquote>

Well if you move the same balance weights farther away from the crank center then of course the balance would change...is that what you're saying?
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Old 03-03-2003, 04:19 AM
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You are correct in the fact that the balance will change.

Flywheel diameter of course would change the balance, so does the thickness of the flywheel but the thickness change is tiny compared to the length of the crankshaft...this is assuming a same diameter flywheel. Am I missing something from the original question? Is the flywheel a different diameter?

When the factory builds engines they don't balance clutch engines different than automatic equipped vehicles, the flywheels are the part that accomodates that with weights placed strategically on it's diameter.

The amount is so tiny that it would probably entail drilling and removing less than a half gram. At some point you have to apply a tolerance to your machining operation? No?

I guess it all comes down to what tolerance for perfection you subscribe too.
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Old 05-14-2003, 12:20 AM
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What about this?

http://www.hotrodders.com/cgibin/ubb/15/006301

Ken
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Old 10-30-2003, 10:54 PM
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Angry 383 stroker balance

Hi everyone, my friend has just had a 383 built from a local engine builder......he was given the wrong flywheel for his Tremec 5 speed transmission. The problem is, we can't find the right flywheel weights. Can someone tell me exactly what to do?
I'm starting from a motor thats in the car, has been driven, now the tranny is out, we have no flywheel on the car. Can someone just tell me exactly what to do with the pressure plate, what flywheel to get, etc...I'm desperate. The engine builder built my motor too and he did a good job, but when we asked him questions he got very mad, and very busy all of a sudden. He proceeded to talk about my friend and I to the local car guys, and he even threatened us! we need some help here thanks a lot....
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Old 03-14-2007, 09:31 PM
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balance confussion

hi i have a 1990 chevy 305 and iv heard that 86 and later that the motors are external balanced and have a one peice rear main seal which mine does my question is what will happen if the motor has a internal balanced flex plate on it what kind of damage am i lookin at the engine has 3400 miles on it and i just found out that it might be the wrong flexplate but the plate that is on there has a good size balance weight that doesnt look like it would be small enough to balance just the flexplate itself but iv ben told it was internal balance but iv seen the same exact flexplate with the same wieght for external applications some help on this would be so great im loosing my mind on this one
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Old 03-14-2007, 09:38 PM
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balance confussion

my engine is brand new its not screwed is it

Last edited by chevy boy; 03-14-2007 at 09:44 PM.
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