When using the single-vacuum distributor, the vacuum hose runs from the vacuum port on the left side of the carburetor to the vacuum canister on the distributor. In that case, the vacuum port on the rear of the carburetor must be plugged.
For most cool season grasses and for folks living in northern climates, the best time to plant grass is in late August, early September. Depending on exactly the climate you have and the type of grass seed you're planting.
In the mid-west that's usually mid-November thru March when soil temperatures are below 50 degrees. Harsh winter weather will not harm dormant grass seeds.Frost seeding is a type of dormant seeding, overseeding moist soil before freezing weather. The natural freeze and thaw cycle of freezing soils will create small cracks or pockets, perfect for catching and holding grass seed.