How low does it go? all the way to 0?? My stock gauge actually works pretty good, reads about 50 psi when crusing, drops to about 20 psi hot while idling at 750 rpm, reads about 65-70 psi when cold even idling. If the pressure only drops at idle may not be super bad, but the knocking thing is really not good. The problem probably lies with the "rebuilt" bottom end. Did you just drop a crank in?? I dropped a Auto Zone crank into my 200k+ miles 305 and I get more oil pressure than the Stang now. All the main and rod bearings were in the middle of the spec range, and I used a new pump. If you have a bad rod, or main cap, the oil press will be poor, or maybe a leaking galley plug, bad cam bearing etc....
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Frank W
90 5.0 LX coupe Daily driver. Silencer removed, K&N filter. Flexalite fan, 3 core radiator. FMS flywheel and Clutch, FMS blue wires Energy Suspension end links
88 Notch 2.3L 5 speed Parts/beater car
My two Notchbacks
74 Chevy Laguna Type S-3 305 Finally fixed getting a 454 to put in garage
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