As Jim suggests
The voltage required to trip the relay is considerably less than the voltage required to "trip" the Starter Solenoid.
What you have left are the contacts of the Starter Solenoid itself which when closed send voltage directly from the Battery to the Starter Motor.
I always refresh (wire brush) the Solenoid Contacts of the Starter Solenoid during a Top End Restoration of the LT5.
This is described in several posts of the signature below. Relay Installation is also described (LT5 Added Systems).