Back on page 4 or 5 of this topic I posted the sizes of my stock, original, '73 455 11-bolt pump, and I quote: "The impeller is nicely cast with 8 well-shaped, properly designed vanes. It is 4.4" OD. The vanes are 0.70" high above back plate at the inlet and 0.50" high at the OD. The inlet tips of the vanes have exactly the same diameter as the inlet hole in the plate, which is 2.4" so the impeller eye matches the hole perfectly. The vane contour exactly matches the plate, i.e. the gap between the plate and the vanes is 0.06" at the inlet and it stayed 0.06" (I checked with clay) right out to the impeller OD. The impeller has 3 balancing holes in the back plate to balance thrust and reduce load on the bearings."
Also, the backing plate is exactly 1/2" above flat surface.
Malcolm
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