355 exhuast stream temps post header collector?

Temp measurements would vary depending on if your manifolds are:

OEM shielded
OEM UNshielded Bare Metal
OEM Ceramic Coated*
Fabspeed polished
Fabspeed Ceramic Coated*

*Black or Silver ceramic

OR painted with a Hi temp paint of Black, Silver or White

Depending on the above ... your temp measurements would range from a low of 300F for OE shielded, to around 650F for Hi-temp Black Paint.

 

I think if you are referring to exhaust gas stream temp at wide open throttle it would be around 1200 degrees ?

 

Is the OP looking for radiated heat in the engine compartment or internal exhaust heat temps?
Exhaust stream temps would vary / 800 degrees F (exhaust port) & up depending on load.

 

At WOT, as the valve opens the EGT is close to 2000dF;
By the time the gas gets to the collector it is closer to 1200dF;
At the cat it goes back up close to 1600dF;
And by the time it gets to the muffler it is down in the 900dF range.

 

I thought pyrometer temp measurements were being taken off the metal surface. If you get an EGT probe before the cat at WOT after full warm up .... the gas stream should measure between 1300F and 1600F.