Harmonic Balancer Options for BOP/Rover Engines

This article appeared in The British V8 Newsletter - Volume XIII, Issue 2 - May 2006

by: James Jewell, with photos & charts by: Kurt Schley

Vibration dampers, harmonic balancers, call them what you may, but most of the common names are a bit erroneous or incomplete. These necessary devices are effectively a combination of counterweight and torsional damper. If an engine's crank is not massive enough to balance out the reciprocating masses, the damper AND the flywheel/flexplate need to be counterweighted in such a way that they help the crank balance the reciprocating masses. Without this, the engine will vibrate up and down, and yaw in an oscillating fashion. On internally balanced engines, the damper has no counterweight mass. The crank also tends to twist and un-twist rapidly along its axis as a result of the firing pulses of the individual pistons. The rubber used in OEM dampers absorbs these unwanted vibrations and actually turns them into low-level heat. Without dampers, a crank will ultimately self-destruct. Cast cranks can self-absorb more torsional stress than forged or billet cranks due to their molecular makeup, and are less likely to fail from this mode.

Kurt Schley assembled the attached photos and spreadsheet on the various GM OEM dampers available to those of us running B.O.P. setups.

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ATI (www.atiperformanceproducts.com) is the only aftermarket manufacturer I could find with harmonic balancers that fit this application.


Photo 1 - 1193961 - Front		Photo 2 - 1193961 - Back

Photo 3 - 578785 - Front		Photo 4 - 578785 - Back

Photo 5 - 1379555 - Front		Photo 6 - 1379555 - Back

Photo 7 - 1199580 - Front		Photo 8 - 1199580 - Back

Year	Model	Engine Code	Trans	Part #	Weight	Photo
Oldsmobile 215
61-62	F85&Cutlass	G	all	578785-or-578784	4.66#	3&4
'63	F85 & Cutlass (2bbl)	G
'63	F85 & Cutlass (4bbl)	G Std
'62-'63	Jetfire	T	all	585642	?	n/a
'63	F85 & Cutlass (4bbl)	G Auto
Buick 215
'61	Special & Skylark	H	all	1193961	6.74#	1&2
'62	Special & Skylark	H, HI	all	1199580	6.14#	7&8
'63 (after 4/1/63)	Special & Skylark	JM, JN	all	1358524	?	n/a
Buick 300/340
'64-'65	300 engine		1365023
'64-'75	300/340/350 engine		1379555		4.94#	5&6
'64-'75	300/340/350 engine		1254811

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Disclaimer: This page was researched and written by Kurt Schley and James Jewell. Views expressed are those of the authors, and are provided without warrantee or guarantee. Apply at your own risk.