68 L78 Holley vacuum advance question

[alben]

My assembly manual for 68 Camaro shows vacuum port just rear of the passenger side carb base bolt on the DZ Holley. There is no vacuum at this port at idle, it opens to a hole above the throttle plates, which are closed at idle. Is this correct, no vacuum is reqd at idle/ Also, my only book showning initial timing advance(68 Chevrolet chassis service manual) shows 4 degrees before TDC is this enough advance? Help will be appreciated. Thanks