Industrial Blower Impellers
The industrial blowers are nothing like an original VR4 impleller besides a similar appearing casting. I have discovered three different dimension impellers used in industrial blowers with this style.
The original VR4 cast impeller are dramatically lighter and stronger than the industral impeller of the same size. They are made in different processes as the industral impeller is a really smooth casting, almost looking billet, but it is a type of casting that is very pourous and actually weaker.
I have the weights of each type of impeller recorded and there is a significant wieght difference with the industrial version even noticable by feel.
The heavy and weaker industrial casting is prone to breaking due to centrifigal force with blower speeds up to 44,000 rpm as in a performance application.
The industrial impeller is also cut at different profile than a true VR4 impeller. More material has been removed on the industrial impeller near the inlet profile, so you cannot make it fit a VR4 cover as it does not have enough material. Also you cannot easly cut down the profile of an impeller on the face of the blades as it would damage the blades trying to cut them on a lathe, unless you use a filler to support them while you change the profile.
Occasionally you see and industrial blower show up on ebay and they sell for way more than I would expect. They are not designed for high speed use, like a SN series blower and would not work well for a car engine. They are originally designed to move air, powered by an electric motor. Why would any one buy one? You cannot effectively use it on a car or use its parts on a SN rebuild.
They also have no interchangable parts with the valuable VR57 & VR58 blowers off the '57 Fords and '57 T-Bird F-code cars. They only slightly resemble them.
I intend on using a heavily modified industrial rear cover cut to match a true VR4 impeller in a converted Ford VR57 with SN converted internals for my supercharged '57 Ford sedan. It will look original on the outside but make VR4 pressures for Nostalgic drag racing and hot street use.