glowing exhaust manifold

my 92 b2200 has had the entire motor rebuilt. but now my exhaust manifold is glowing red when ran for a long time. the temp is cold on the temp. gauge (thermostat has been removed) and the pipes have been gutted. The cat is empty right below the manifold. And at the bottom of the manifold is where the heating starts. timing is set. any ideas that would make the exhaust manifold get hot like that? need help! pls

There are 2 catalytic converters on this truck. First one you gutted out and the second one before the muffler. Second one could be plugged up too. Check your O2 sensor, it could be bad and giving it a rich mixture and can plug up your cat really quick.

There are 2 catalytic converters on this truck. First one you gutted out and the second one before the muffler. Second one could be plugged up too. Check your O2 sensor, it could be bad and giving it a rich mixture and can plug up your cat really quick.


thanks for the info. The 02 sensor is black when I took it out. There is no second cat or muffler, just straight pipes to the end. With the first cat being completely gutted would this be holding heat. Or is the 02 sensor just bad?