PLEASE... EXPLAIN ME BETTER WHAT IS YOUR POINT... brand, year, why, what are you trying to do...

Im trying to replace pilot light control.I pulled it out but the cast iron burner is still attached The unit is probably 30 years old maybe older The pilot will not stay lit when I pull out the button to start heater.Let me know what you think. Thank

You have to check first : the quality of the pilot flame, often the pilot is dirty and the flame is not enough to heat the thermocouple. If you see that you have a small, yellow or orange pilot flame, close the gas, open and clean inside de lilot with a compressor and try again, always be sure first that you don't have any gas leak before, be careful. Also change the thermocouple. It gives millivolts to te main gas valve to keep the pilot on. If is too old millivoltage is not enough to keep the pilot. The burner normally is attached to the body by some bolts, put a mirror down and you are going to see the bolts, is not a funny job. Give me some news and always be careful. If you are not sure call a tech. Don't forget gas is explosive!! Care about leaks. Once tou take out the burner also clean it.

Don't try to take out the main gas valve until you are sure that the other 2 things are OK, If you have to do it you must replace the control and I suppose that you actually have an old MGV, so you have to find a replacement, it's going to be smaller and you also have to modify the pipes a little bit. I repeat: is not a funny job.