I've seen several threads about tips and tricks when installing the new Crawford cast plenums, but it seems that the most important one of all has been missed. WASH IT WITH SOAP AND WATER. I never see anyone mention this. Mine had a lot of sand/grit on the inside of the plenum. I gave it a nice cleaning with warm soapy water and a sponge. All that stuff will wash right out, just don't forget this step. You don't want this grit going into the motor.

 

Thanks. Good tip.