Wally
Thank you for your reply to my posting. Yesterday I called our local gas company, PSE&G and they sent out a technician to look at the problem. He used a device that detects gas and found that when the valve controller was set to the pilot position a small amount of gas was leaking from the four outlets in the manifold into the space where air mixes with gas before it enters the tubes. That is not supposed to happen.
He replaced the valve controller, adjusted the pilot light and the main gas flow. That seems to have cured the problem.
Perhaps as you said the mixture of gas and air was also incorrect which caused the gas to ignite at the end of the tubes near the manifold and make a roaring noise.
Thanks again for taking the time to reply to my posting.
Wally
