There at at least 3 different types and a bunch of different sizes (diameters) all used in the same casting. The same casting was used on many
different engines. As far as the number of vanes on the impeller I have never paid much attention. I sure that the cast impeller has more than 5,
6, or 7 vanes.
The GMC 455 came with a cast impeller at 4.25 inch diameter (I believe). I have one in my hangar and I'll try to remember to look at it tomorrow.
I believe the larger impeller was used on engines that needed more coolant flow. A lot of people have installed smaller impeller pumps and do not
seem to have a problem with them other than initially getting all of the air out of the system.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
