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.
The best time for planting grass seed in Missouri is between Aug. 25 and Oct. 10. Keep in mind that lawns seeded within a week of Labor Day are more likely to fill in completely for winter and produce a thicker, denser turf appearance for the following spring compared to lawns seeded in October.