[FC] Harmonic balancers....

[James Davis]

More info to add to Bob's comments.  The maximum rotational vibration 
of the 2.6 inch stroke crank is listed in SAE140C as 0.5 deg @ 4,400 
rpm (the sixth harmonic of the cranks resonance frequency).  The 
longer stroke 2 and 15/16 inch crank has a greater rotational 
vibration with a greater amplitude at a lower rpm due to its 
increased mass, less rigidity, and input pulse intensity (more 
torque).  I have no specifics on just what the maximum stress might 
be, but using some rough guessing I would estimate the sixth harmonic 
of the long stroke crank to be 0.67 degrees @ 3,900 rpm..  So if you 
never exceed 3,200 rpm with a long stroke engine you should stay in 
what GM considered the safe operation zone for engines without a 
harmonic damper.
Jim Davis


.At 09:42 PM 6/29/2007, Merv Krull wrote:
>Hi All!
>
>Just wondering.... is a harmonic balancer a good idea for all 
>Corvair engines or are there some engines that it would actually be a problem?
>
>The ever so smooth running car engine that was transplanted into my 
>GB has a YN in the code to make it a 61 98 hp or a 62 102 hp or a 63 
>102 hp or a 64 110 hp.
>
>It has a draft tube, but the shroud has a patch over the pcv hole 
>and the balance tube between the carbs  has the pcv nipple covered. 
>That rules out the 61 and 62 versions (maybe).
>
>It has a solid pulley, which makes it a 61 or 62 cuz the 63s all had 
>harmonic balancers.
>
>Like some folks have already pointed out, I need to read the numbers 
>on the heads to be sure.
>
>But back to the question. Should I leave the solid pulley on or 
>order a new harmonic balancer?
>
>toodles
>Merv Krull