Quote Originally Posted by 76GMC1500
Man, my 350 doesn't make enough heat. It takes 10 minutes to get up to a high enough temperature to open the thermostat. The old engine did it, a new engine does it. It makes it hard to time the choke because it takes so long to warm up.

Your fix may be as simple as a new thermostat.

Test the old one and the new one in a pan of boiling water.
You can check the opening temperature with a candy thermometer.

Candy thermometers are reasonable in cost and fairly accurate.
They also work well for checking the coolant temp in the radiator so you can see if the car's gauge is indicating correctly.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

As far as drilling holes in the thermostat flange, one is enough.
Two 1/8" holes in the thermostat flange will take about four miles of 35-40 mph driving to get the coolant temp up to 180 or so on a 16 degree F morning (in a roadster).
One 1/8" hole takes about one mile on the same road and speed with the ambient also at 16 degrees.

Been there, done that....