440 source aluminum water pump housing, Big block..

Check the internal passages of either AL housings to a cast iron OEM. There was a rash of posts about inefficient pumping through these as one of the cast passages was very restricted. From Duster44D back in 2013,

"...Externally the housing looks fine but the engine supply ports (lower openings) are very restrictive. You're kidding right....how can this be ? Nope...they are poorly designed and you'll see it yourself once you pull the pump housing and stick your fingers down the hole.

So, over the w/e i pulled the rad and all the front acessories off the engine to have a peek...sure enough the lower (supply) ports were very small. I compared this to the stock housing and it was like night and day ! On the stock housing i could easily get 2 or more fingers all the way into the hole but on the Source housing i could only get one finger in maybe an inch and it was jammed....WTH !!!..."

post #14 Aluminum Water Pump Housing