That cam shouldn't need 20 degrees of initial timing. As an example a 256 @ solid cam with 320 adv duration making 9 inches of vacuum with a 108 LSA needed 22 degrees of initial timing.
Neither should it need 40 or more. Every degree before TDC you ignite the mixture is wasted energy not applied to the crank when it can translate to forward motion. High Idle timing is a function of too much overlap and too much exhaust residual in the chamber requiring earlier ignition because the mixture is diluted or lean. LEAN MIXTURES BURN SLOW!!!!!!