Hot Rod Forum : Hotrodders Bulletin Board - View Single Post - broken crankshaft
View Single Post
  #16 (permalink)  
Old 10-10-2012, 11:40 AM
oldbogie oldbogie is online now
Registered User
 
Last photo:
Join Date: Apr 2007
Location: Seattle, Wa
Posts: 7,081
Wiki Edits: 0

Thanks: 4
Thanked 536 Times in 453 Posts
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
Reply With Quote