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  #16 (permalink)  
Old 10-10-2012, 10:40 AM
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QUOTE=atcoscrazyest69;1597869]Well i planned on gettin her all cleaned up. Ok just so i got this right if i get this kit Eagle Specialty Products B13470030 - Eagle Street Performance Rotating Assemblies - Overview - SummitRacing.com i will not need to get it rebalnced? Just put inu and go?
Thanks for all your help guys![/QUOTE]

This is an internally balanced kit it will require you add the proper for internally balanced crankshaft the zero balanced damper and flywheel or flexplate.

Letís talk internal and external balance for a couple sentences. The definition is that the internal balanced crank carries all the counter balance on that portion of the shaft that is inside the crankcase. This is not to say that the balance is by cylinder to cylinder but is overall balanced within the crankcase. Externally balanced crankshafts typically do not have sufficient space within the crankcase for all the counter balance so some portion of the needed counterbalance is hung outside the crankcase. This usually applies the needed counter balance to either of both the front damper and the rear mounted flywheel or flexplate.

In the case of the internally balanced crankshaft the damper and flywheel or flexplate are what is called neutral balanced. That is they have no offset balance and may be used on any engine they will fit to that also has internal balance.

The externally balanced engine uses a damper and flywheel or flexplate that is offset balanced. That is it is out of neutral balance and may only be used on matching engines for which they are intended.

The failure of a crankshaft through the forward rod journal faces is mostly caused by the failure of the damper to perform its job. The damper is intended to absorb the alternating energies on the crankshaft caused by the power adding or power using strokes of the many cylinders. These cause sizable vibrations in the shaft that need to be absorbed which is what the damper does. If it fails in the case of a factory unity it will be a hub and ring that are separated by a rubber ring. When the rubber fails or if the hub doesn't fit snugly on the crankshaft, it stops absorbing these wild vibrations and the crank snout starts to orbit rather than rotate. This motion will bust the shaft usually just behind the number 1 main through the cheek that supports the number 1 rod journal. Carving out the number one main bearing thus starving the number one rod bearing of oil and the subsequent failure of the rod is also a common event.

There's more to say but I need to run, this shoud give you some food for thought.

Bogie
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  #17 (permalink)  
Old 10-10-2012, 10:43 AM
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Quote:
Originally Posted by atcoscrazyest69 View Post
The link i posted is a 2 piece rear seal? And i understand the balancer and flywheel stuff but in the link i posted it also says it is balanced so i am confused
Yes sorry, I was looking at the pic which is 1 piece, the description says 2 piece. They do come with a "balance" from the factory, but from what I hear they are not a good/accurate balance. More than likely they have a target weight/balance for each part and if they fall into a certain tolerance it is good to go, meaning the entire assembly/collection of parts you get is not holistically balanced. You can chose to trust the Chinese balance, but it is not suggested for any performance or RPM use. Low RPM grocery getter you are OK.
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Old 10-10-2012, 11:31 AM
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I just talked to the guy at summit and he said theres no need to get it balanced. That the units are balanced he just said use a 350 balancer and flywheel and its good to go
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Old 10-10-2012, 11:39 AM
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use a good balancer and flywheel and make sure they are balanced too
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Old 10-10-2012, 11:44 AM
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I dont understand why theres this balance factor. So your saying i SHOULD get everything balanced crank flywheel balancer rods pistons?
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Old 10-10-2012, 11:56 AM
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yes,absolutely anything that spins.
when you get new tires they get balanced too
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Old 10-10-2012, 12:01 PM
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No. No they dont lol
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Old 10-10-2012, 12:04 PM
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Yeah I read it the same way, a complete balanced rotating assembly.
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Old 10-10-2012, 12:19 PM
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So it shouldnt need more right?
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Old 10-10-2012, 12:22 PM
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When you order the kit, get the recommended harmonic damper and flywheel from Summit also.
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Old 10-10-2012, 12:39 PM
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Quote:
Originally Posted by atcoscrazyest69 View Post
I dont understand why theres this balance factor. So your saying i SHOULD get everything balanced crank flywheel balancer rods pistons?
Read Bogie's post again....

Duke
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Old 10-10-2012, 12:56 PM
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That "kit" is already balanced according to the ad. Eagle DOES sell pre-done "drop in" kits. I would guess it's one of them. Call Eagle and ASK.

I would not recommend that kit. It has a cast steel crankshaft. Those are the ones we've seen problems with. They're not as rigid as a factory nodular crank, and not as elastic as a forging. In our industry, when the word "steel" is used to describe a crankshaft, "forged" is implied. Engine builders, except those trying to mislead for a sale, won't call a cast steel crankshaft a "steel" crank. They'll include the word "cast".

If you DO buy it, as SS says, you'll need a new balancer and flywheel/flexplate for "internally balanced". The stock 400 stuff WILL NOT work.

Jim
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Old 10-10-2012, 05:33 PM
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I understand the external balance points with 400s and 383 as it is on a 4 speed trans and i had to buy that plate that bolts between the flywheel and crank. I understand that the balancers are different for the externally balanced 400 and all the other internally ballanced motors. The whole reason for trying to make it internally balanced is i do not like having to run that balance plate. I just dont understand why the add says its balanced and a couple fellas on here are saying send all the brand new stuff out to get balanced. If i have to send it ourmt to get balanced either way then theres no need for me to get a whole rotating assembly the only reason i said id get the assembly is because it states its balanced. I just donot know what to do. But i do not want to do it again
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Old 10-10-2012, 06:06 PM
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Quote:
Originally Posted by atcoscrazyest69 View Post
I understand the external balance points with 400s and 383 as it is on a 4 speed trans and i had to buy that plate that bolts between the flywheel and crank. I understand that the balancers are different for the externally balanced 400 and all the other internally ballanced motors. The whole reason for trying to make it internally balanced is i do not like having to run that balance plate. I just dont understand why the add says its balanced and a couple fellas on here are saying send all the brand new stuff out to get balanced. If i have to send it ourmt to get balanced either way then theres no need for me to get a whole rotating assembly the only reason i said id get the assembly is because it states its balanced. I just donot know what to do. But i do not want to do it again
That's reasonable; I'm not enamored of externally balanced engines, therefore, work hard to keep 400's and 383's internally balanced.

The kit you sight is internally balanced and will, therefore, require that you purchase a netural balanced flywheel and damper.

The raging argument about how well balanced is one revolving around how good is good enough. Some of these pre-balanced kits have been miles off. Sometimes this is the result of the manufacturer other times it's been the fault of the builder taking to much material from the rods or piston skirts in the pursuit of clearance. Frankly, I prefer SCAT to Eagle when it comes to budget bottom end parts and assemblies. But since you're dealing with Summit, they have a very good customer service reputation so I'd mentally lean on them with this provisio; if you have interference between the rods and cam or piston skirts DO NOT FIX IT. Call Summit and make arraingements to return it in the original packaging in a clean and unmolested state. That eliminates any argument over who did what and has blame. Grinding on the rods and or pistons will alter their weight destroying what ever level of balance they came with. Mayby not by much, but you don't want to get caught in "if you touched it, its yours".

One thing we see a lot of when sending parts to our balancer is that many things that are sold as balanced (including flywheels, flexplates, and dampers) are often well off any reasonable standard for a performance to competition level engine. So we do not even bother with pre-balanced kits. We procure things in pieces, make up assemblies, proceed to a mock-up build that trims parts if necessary, mark them as to where they go and who goes with whom, then have them balanced. This is tedious and adds some cost but the end result is a correctly balanced engine, whether that's spot on or over/under balanced by end use or customer desired requirement. For a mild performance street engine that doesn't go over about 6 grand of RPMs, spot on is the place to be no over/under balance games needed.

Bogie
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  #30 (permalink)  
Old 10-10-2012, 09:34 PM
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Thank you bogie. I think that is exactly what iv been waiting to read. Im gonna get that crank theres no need to get the whole assembly and im gonna drop off the crank flywheel and balancer at the local shop. Thanks for all your help
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