If it works for you then great but just note that the other reasons using a grill cover is right (besides stress on the radiator) is because then the air is still able to circulate if necessary but still stops the direct blast of freezing air on the aftercooler, radiator, and intake. If you just covered the radiator with cardboard then not only is the radiator not getting proper air flow but the aftercooler is still exposed. Thats bad because the aftercooler should be shielded to help keep intake temps up for proper combustion. If your intake temps get to low then you can not only affect performance but fuel mileage as well. All depending on how cold it is too.

In all honesty, I've never had to use a grill cover. It doesn't ever get that cold anywhere around where I live. The "right way" information I'm sharing comes from the many threads I've read from guys who do use them and have explained the do's and dont's.

 

I used to put a sheet of cardboard between the intercooler and radiator. I never had any ill effects, and the EGT's were not unusual. I don't haven't done it yet this year, mainly since my wife recylcled my cardboard this summer.

I'm sure that with the radiator blocked off, it also reduces the flow through of air through the intercooler, since there is a large restriction in the air flow path.

 

It's for a pre 96 7.3 PowerStroke. (Lol) I grabbed the short stem version. It's just a cheapie from Advanced Auto, a Stant. I wanted to see if it would work before buying a nice one from DieselSite. I had to mod it a bit, (Shave the shroud to a smaller diameter) but so far I love it. It keeps the Cummins right around 190 on the gauge but warms up a lot quicker. Gets rid of the cycling issue in the winter with a boatload of ice cold coolant crashing into the water jacket when the stat is fully opened. It still cycles, but it's a bit warmer so the shock isn't as bad. Good heat soak when I duck into a store. It's nice so far.

This is my third winter with it and the cheapie is still working.

 

Necessity is the mother of all invention.

 

cold today, 4 when I left for work.
plugged in all night. Un plugged it started it up and let it idle for about 5 min.
4 miles had fair heat, 6 miles pretty good heat.

sat at work for 13 hours at 14 or so.

6 miles, fair, 8 miles good.

so the new thermostat and flushing of the heater core made a HUGE difference.

Also, I wanted to say that is the easiest thermostat I have ever changed.

thanks for all your advice and input.