Regarding the "small orifice" we've all seen on older 3-port pumps, here's an update for you. The Carter M4690 no longer has the plug in the tubing with a small drilled hole in it. That's gone. The return line port is simply a one-inch-long piece of 1/4" thin-wall tubing welded to the bottom of the main can. Pontiac may have specified a controlled-bleed port back in the day when AC-Delco made these pumps, but that feature is gone from the current Carter pump!
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