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: To know when to apply a weed preventer you first have to know when the seeds you are trying to prevent are likely to germinate. Crabgrass seeds need several days of soil temperatures higher than 55 degrees in order to germinate. Most years in Atlanta, March 15 is the date experts recommend you apply the pre-emergent. Only the most shallowly buried crabgrass seeds will be sprouting then but many more will germinate in April and May.