<VV> Harmonic Balancer or not?

Brent Covey brentcovey at hotmail.com
Tue Jul 18 16:02:03 EDT 2006

Hi Everett,

>   The main issue is: I have an early type a/c pulley that is cast as part
of the crank pulley.  I had never seen one of these before.  I plan to use
it if the potential for engine damage is unlikely.  Im thinking that the
revs never get into that high performance vibration creating area that a 110
in a car might.

I would not run a long stroke (164) FC engine without a harmonic balancer-
GM used the very best balancers of the run (the ones usually reserved for
Turbos) on the FC so must have felt it was very neccesary. Given the
extended time you can spend at high RPM and heavy throttle on long hills or
into headwinds etc, I would think the need for a balancer on the FC probably
is greater than on a passenger car.

The potential for damage is still fairly low, but its cumulative damage, and
the type of damage is total engine failure- the cranks snap off and parts
get mangled inside. This is a rather high risk to run for a small return.
The balancer is certainly a good investment for peace of mind.

Something you might want to consider is finding an AIR (smog pump) pulley
off a 1968-'69 car that bolts onto the balancer- its a smaller diameter than
the a/c pulley and makes the compressor load a little lighter because it
turns it a little slower. They're easy to find used and not worth much,
probably $5. This would also give a little more clearance for changing belts
etc. The cast early a/c pulley you have now is a $5 part too, so no big loss
if you dont use it.
>   Oh, and as long as Im asking....is the cam on the FC different than the
car engine of similar year/output?  Would that make a difference in the
above question?

FC 110's apparently are high compression 95's but I havent confirmed this
personally- this would be 110HP heads and the 95 HP 3839889 cam. The 95 HP
distributor would be a correct curve for this combination if thats what it
is. This would be a pretty torquey engine that would really want premium
gas, the cylinder pressures would be very high, and it would be very
sensitive to octane. You will want to experiement with vacuum advance units
carefully to find one thats complimentary as well. HP output would be a
little lower than a passenger car version with the 3839891 (140 MT/1964
turbo/most 110HP's) cam.

Theres some other details different on FC engines like the oil filler is
relocated and theres positive exhaust valve rotators.

Hope thats some help, good luck,
Brent Covey
Vancouver BC

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