Dusterbd13 MegaDork
10/18/18 9:11 a.m.

So, in looking at going serpentine with my small block mopar, i had an either incredibly genius/incredibly stupid idea.

Realistically, i cant afford an off the shelf solution. The magnum serpentine belt system swap won't work for me either.


Can i take the impeller for the magnum (reverse rotation) and put it in the older housing (standard rotation) to make the reverse rotation bolt on water pump i would need?

SVreX MegaDork
10/18/18 9:18 a.m.

In reply to Dusterbd13 :

Wouldn’t that depend on the inlet and outlet flow and the shape of the chamber?

Picture a turbo. A backwards impeller isn’t going to spin the opposite way. It’s just gonna perform crappy. 

SVreX MegaDork
10/18/18 9:21 a.m.

It MIGHT work... depending on the design

Rodan HalfDork
10/18/18 9:21 a.m.

Not sure about swapping impellers, but when I did something similar on a Ford 302 years ago, I was able to find a water pump off an earlier, non-serpentine car that had opposite rotation.  I then found a pulley that worked with my serpentine setup.  Maybe $50 in parts...

¯\_(ツ)_/¯ UberDork
10/18/18 9:22 a.m.

Photos of the impellers and housings in question will make it a lot easier to give an educated guess.

SVreX MegaDork
10/18/18 9:25 a.m.

Aren’t you gonna flow backwards?

On most cars, that means you would feed the cold water into the heater core, then luke warm water that was very restricted in flow into the block. 

zordak Reader
10/18/18 9:37 a.m.

In reply to SVreX :

Centrifugal pumps will usually still draw from the inlet and discharge at the outlet no matter what direction the impeller is turning. The problem arises from impeller design. Reversing an impeller designed to turn one way will result in really poor performance the other.

81cpcamaro Dork
10/18/18 9:39 a.m.

On most reverse rotation pumps, the water passages are different as well, so I would think just swapping the impeller wouldn't work like you need it to.

Curtis UltimaDork
10/18/18 9:46 a.m.

Look to the marine world, too.  Again, you have to be careful about impeller design.  I'll try to break it down for you.

Pre-74, you could find small blocks from all of the big three in boats that were reverse rotation OR forward rotation.  In some instances, they designed water pumps with impeller vanes that were reversed for the reverse motor.  In other situations (primarily Chevy I/O applications, but all three a possibility), they beefed up the water lift pump in the outdrive and made a straight-vane impeller that works equally crappy in both rotations and called it a "circulation pump."  The primary flow came from the outdrive and the water pump on the block just moved enough to keep it flowing through the block.  The straight-vane pumps don't do enough flow to be the sole pump, but if you find an old mopar water pump that is designed for reverse rotation, you have your huckleberry.  Try ebasicpower.com

I have to think, though, that there is an easier solution that Dodge already made for you.  When they went serpentine, wouldn't they have already come up with a proper pump?

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