When the steering system on an Ace or Aceca is working correctly it should not be overly heavy. However I've found the following issues to be the cause of both heavy steering or wayward handling. Badly adjusted or setup steering boxes, bent outer & inner steering columns, binding steering idlers or ball joints, excessively wide wheels & tyres.
Another problem I've come across is the incorrect fitment of the front uprights. These are handed but are sometimes swapped over, leading to negative castor & subsequent terrible handling.
The uprights are also prone to accident damage also effecting castor angles. I've also seen a couple of Aces with the front suspension tower bent backwards from accident damage. This has the effect of increasing the castor angle also leading to heavy steering.
I believe your car is fitted with a Zephyr engine & should therefore be fitted with uprights that have only 3 degrees of castor, unlike the lighter engined AC & Bristol powered cars that were fitted with uprights giving 5 degrees. The 3 degree uprights also seem to have been fitted to the heavier Aceca.
Anyway, it's worth having a closer look when you strip the car down to do the kingpins.
Regards Luke.