[Marshall V. Daut]

Fully retard the spark lever during idle and run the RPMs up via the hand throttle above normal idle speed. Keep the throttle lever there for a couple minutes. This will make the engine run "late" and help warm it up faster. You could also slip a big piece of cardboard between the radiator and the headlight bar to block air flow through the radiator that cools the engine. That will help warm the engine up quickly, too. Just keep an eye on things so that the engine doesn't start to overheat.
It is not normal for a Model A engine to take as long as you describe to warm up to operating temperature in the climate where you live. Until you can find the cause for this and fix it, the above mentioned "tricks" should reduce warm up time drastically.
Marshall