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.
A moist, firm seedbed is required for prairie grass or prairie grass-legume mixtures. Spring or summer seeding of prairie grass are recommended in Pennsylvania. However summer seedings should be completed by early August in the northern half of the state and by mid August in the lower half of the state.