so i was wondering, will a 13b water pump work on the 12a. would there be any advantage of putting the fc pump on a fb (possibly better pump design).

 

I think you'll that the biggest difference between the 12A/13B is the radiators. Water pumps are nearly identical.

 

there's one bolt that's in a different location on the fc pump vs the fb pump. at least that's what i found out when putting an s4 pump and housing on my 74 13b. as for an advantage, there would be none. it just circulates water. one doesn't do it any better than the other. the only reason i did what i did was a suggestion by the friend that was helping me build the engine in keeping the "cast, aluminum, cast, aluminum" theme throughout the engine from w/p to rear housing. we didn't think they'd be any issues since the upper rad hose neck from the 74 would bolt the same to the s4 pump housing. we made it work but if had it to do again, i'd just stayed with the original 74 setup cause it created lots of problems with the fan as well cause the aluminum spacer on the fan from the 74 wouldn't fit right on the s4 pump to center itself causing a weird vibration once the rpm's got high enough that the pump housing bolts would vibrate loose causing the gasket to leak. not to mention ruining all the work i spent on painting the engine. moral of the story, stick with what works.

 

The impeller on the earlier pumps was better. They used a cast design whereas later pumps used a stamped steel. Not sure if the switch was made for FC's or FD's.

 

ok thanks i guess ill just stick to the original, i didnt know if the design of the blades in the impeler were different or anything