Hmmm, is there an alternate route to access the cooling system? Maybe rig up something to tee into a heater hose, radiator hose, unused threaded port? It won't make much difference where in the system you take a pressure reading, just compare cold start pressure to that while it is warming up. Or, fabricate a rubber expansion plug to fit in your radiator opening and drill it to accept a gauge?
1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy
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