Have you tapped, THUMPED the gauge to see if the needle moves, just a thought, also the water pump pulley my be an issue, mine is overdriven


1968 Charger COLD A/C Hilborn EFI
512ci 9.7 compression, Stealth heads, 4.10 gear A518 ODtrans 4100lb,10.93 full street car trim
2020 T/A 392 Stock 11.79 @ 114.5