Make sure you are getting a good draft at the burners. If you don't have a draft gauge, take a newspaper, roll it up and light it when the burners are lit.
Once it starts to burn blow it out, hold it about 6" away from the burners and see if the smoke is drawn into the flame. If it does, then you have good draft, if it doesn't then you may have a blockage in the heat exchanger or in the flue pipe.
Placing a plate over the burner is ok as long as you have proper draft. If you don't, then the plate will get hot and warp over a period of time.
Originally Posted by johnrdila
Thanks for the reply. I agree with ur assessment. I found an old manual in the basement. The machine is circa 1981. From the photos I can see that the burner door is missing on my unit. I plan to make one out of metal to replicate the original. Case closed. Thanks again.