366T/Holley 4160 Governor?

1973 GMC 6500, 366T, with Holley 4160-style vacuum sec four barrel. The carb has an oil pressure governor on the secondary throttle vacuum actuator, and it appears to also affect the distributor advance mechanism.

Any idea where I can get data/diagrams on this system? I've got a spare 4150 with single line adapter and could probably scrounge a breaker point distributor for it if necessary, but I'd like to know something about this system first.

Take the distributor out and look under the breaker plate. There is a barrel weight that pushes against a spring from centrifagul force until it seals off a vacuum port that will close the throttle until the RPM drops and uncovers the hole again. The hole commonly gets plugged up causing the throttle to stay closed.