You might also make sure the thermostat isn't stuck open. If it is slow to warm up the heat riser and thermostat are 2 of the most common problems. You also have to remember that it takes longer to heat up 700 pounds of steel than it does 300 or so pounds of steel and aluminum in newer lighter engines.
If you think your 235 runs cold for too long try waiting for the V12 diesel in an M60 tank to warm up.