I got an aluminum godspeed radiator and it does not have a radiator cap/not just the cap, no neck either. Is it necessary with the way the coolant system works on the fd to have a radiator cap on the radiator of the car, or can you just use the cap on the water pump? Sorry if this is a dumb question

 

Not entirely sure what you're asking but there is no cap on the FD radiator. Only on the waterpump housing.

Get a 1.3 radiator cap.

 

You don't need a neck/cap on the radiator.

 

no cap on the radiator thats how we roll