1649 1970-1981 Pontiac Buick and Olds "11 Bolt" water pump

Classic Pontiacs run hot.  Flowkooler designed a high flow 11 bolt pump  with a CNC machined billet impeller to increased vane count and reduced backing plate-to-impeller vane clearance.  It achieves greater flow rates, higher head pressure, a more efficient flow and it can be used with the serpentine conversion kits The impeller color is due to Type II Class II military grade surface coating which protects against corrosive fluids. 

FlowKooler introduced the first hi flow pumps and continues to improve impeller design. Why is increased flow so important to cooling a hot Olds Rocket engine? Because it has been proven time and time again that reducing the cycle time between the heat source and the heat sink creates more opportunities to shed heat and drop engine temperatures.

From 0-3,300 RPM…Nothing Beats a FlowKooler!

Reducing the gap between the backing plate and the impeller

Way back when the internet was young a George Kujanski made a statement on a forum about his experience in reducing clearance between impeller vane and backing plate.  Ever since our phones ring with questions about the clearance.  George was correct; when you reduce the clearance in a centrifugal pump you will increase the pressure differential and, concomitantly. increase the flow.  We machine taller impeller vanes into our pumps for this very purpose.  However as a manufacturer, we cannot machine each pump for the myriad of aftermarket plates and/or distorted, warped or corroded OE plates.  Furthermore, we cannot ensure that the person modifying has experience in forming metal.  For this reason we will not make a recommendation beyond; "as close as you can get without touching."

George pressed his plate to a .100" clearance and reported anecdotally, "a drastic change in my engine temps with no other changes".  As a frame of reference, this is roughly the thickness of three sheets of paper.  If you elect to close the impeller-to-plate gap you have George's blessing. 

N.B.  Clearances that results in an impeller vane to backing plate interference will cause friction and failure and so we (unlike George) cannot recommend a specific clearance.  Owner modifications to the Pontiac part design are performed at the owner's discretion and FAILURE TO MAINTAIN ADEQUATE CLEARANCE WILL VOID ALL WARRANTY.

*Note: Do not buy this pump for the 1969 400 blocks with casting #9796351.  The 1969 400 pump measures 4" and the correct pump is 1647