95 350 Chevy sub. exhaust manifold

What can be causing exhaust manifold to be glowing red hot?

Heat. It can come from extremely hot cylinder operation, such as when you’re operating really lean (like stoking a fireplace with a bellows, added oxygen makes the fire hotter). Defective oxygen sensors are a possible cause.

Also, if the exhaust is plugged the heat will be retained, build up, and heat the manifold. Plugged cat converters would be the first place to look.

Have you been having any preignition problems…pinging or knocking? Preignition, in addition to being caused by hot cylinders, can also be the cause of hot cylinders.

Carbon buildup. Carbon retains heat. Works great for bar-b-que briquettes, not so great in engines. Carbon buildup can also increase conpression, adding to the heat.

Got codes?

I’d start by looking at the exhaust.

Thank you very much for the infomation that you were so lovely to give me. I will make sure they all of this is checked out. So thank you very much and I am sure I will have many more questions to come later on. Sweetlovinmoma