Water Pump Back Plate

[Lawrence Berte]

Anyone know if the back plate of a 1970 300HP 350 is flat, or countoured, and if the impeller is cast iron or stamped steel.

[Joe L.]

Re: Water Pump Back Plate

Lawrence-----

The backing plate for the "608" waterpump used for all Corvette small blocks in 1970 had a raised area surrounding the flange which mounted to the waterpump. The raised area was just about the size of the plate excluding the flange area and the raised area was otherwise flat. The flange area had narrow indentions between each bolt hole. The purpose of the indentions was to improve sealing of the plate/gasket. Many earlier backing plates did not have these indentions but were otherwise similar to the 69+ configuration. The completely flat plates were used on much earlier "608" and other much earlier Chevrolet water pumps (50s and very early 60s). The completely flat plates and the later style without indentions do not seal nearly as well as the style with the indentions.

ALL 1970 and earlier Chevrolet waterpumps used castiron impellers. Many Chevrolet waterpumps after 1970 also used cast iron impellers. From about the early 80s onward, stamped steel impellers were used on PRODUCTION and SERVICE waterpumps.

[Lawrence Berte]

Re: Water Pump Back Plate

Thanks Joe
Any chance the correct back plate is available new.

[Joe L.]

Re: Water Pump Back Plate

Lawrence----

No, this plate, as a seperate part, was discontinued more than 30 years ago. They're very easy to find on used or rebuilt waterpumps, though.

[Jack H.]

Re: Water Pump Back Plate

If memory serves, both Corvette Central and Chicago Corvette list different levels of water pump rebuild kits that contain bearing, seal, backing plate, screws and gaskets as well as a 'super kit' that kicks in impeller and shaft....

But, Joe's right! A water pump core can be obtained from your local scrap yard for something like $10 and give you the parts you need IF it's not seen a prior rebuild with mixed parts. This means you need to be able to visually ID a 'correct' original before you make that yard purchase....