<VV> Turbo retard unit adjustment, is there such a thing?

[Carlton Smith]

I have been curious for awhile about the specifications for the turbo retard
units. The Ignition Spark Curve Chart in Service News 1962 to the 1965
chassis manual are the same indicating the pressure retard starting 0°@ 2
psi and Full Retard (+ engine) at 12°@ 4.5 psi. However, in 1966 this
changed to 0°@ 2.25 psi with Full Retard (+ engine) of 8°@ 3.62 psi. I
cannot find that GM published an updated Ignition Spark Curve chart in 1966,
yet the specs did change on the pressure retard unit. The mechanical advance
specs stayed the same. As far as I am aware the 65 and 66 180 hp engines
were identical. But obviously GM changed the pressure retard specs. on the
final year probably for a reason. As far as I know the pressure retard
units, on the late models 65-66 units were the same with the 250 stamped on
the actuating arm. So how does one adjust the pressure retards to the last
66 specification? I would think this difference would greatly affect
detonation prevention.

Carlton Smith
Indianapolis, IN
Circle City Corvairs Club
1965 Corsa 180hp Turbo Convertible