i have an 302 out of an 87 grand marqious with a serpentine belt, the water pump pully is ribbed and not flat. what direction is my water pump spinning

 

The 87 ,the water pump turns backwards from the old ones you can
swap to the old one.

 

well i recently took off a water pump from a 79 lincoln and the blades are the same as the marquios. would i have the change the timing chain cover if i switch from a reverse to standard rotation water pump?

 

I see this all the time in the parts business. The castings on the 302 water pumps are the same for a standard rotation pump and a serpentine reverse rotation pump. The difference is the impeller. A lot of folks get confused on the belt design thing. A ribbed flat belt is NOT always a serpentine belt. The term serpentine refers to the routing of the belt, not it's construction. Basic rule of thumb is if it is a one belt runs everything set up, it is a serpentine belt and usually runs a smooth water pump pulley in reverse rotation. If memory serves me, Grand Marqs and Crown Vics came with flat belt standard rotation water pumps with ribbed pulleys in the early 80s and switched to the one belt serpentine system with smooth water pump pulley and a spring loaded tensioner in the later 80s coinciding with full EFI. Probably the best thing to do is find a cooperative parts man and compare your pump to a known reverse rotate water pump {such as an 87-93 5.0 mustang} looking at the impeller to be sure. When I do small block swaps I always try to get all the pulleys and brackets from one donor car and remember what that car was for future parts needs like belts and pulleys. Mix and match can be a nightmare !

 

rule of thumb if there is one belt serpentine (multi ribbed) the water pump is reversed if there are 2 belts the pump goes clockwise as the motor turns and there is a difference in pumps and timing covers and they don't interchange!!

 

The full size Fords/mercs used standard rotation until they went to over head cam engines in 1992.

 

wtroger is correct.
I checked it out today in the parts books!