What is the sphere in my skid plate?

[85powerram]

I have a 1985 w100, I was under my truck putting long tube headers on and noticed a sphere with hoses going to it behind a tin shield. I have no idea what I could be. Any ideas would be helpful, thanks!

 

[Sherman Bird]

I have a 1985 w100, I was under my truck putting long tube headers on and noticed a sphere with hoses going to it behind a tin shield. I have no idea what I could be. Any ideas would be helpful, thanks!

That's the byrillium girdle spring container! Just kidding!
If it is black plastic, and the hoses are very thin vacuum hoses, that is the vacuum reservoir for the Ventilation mode function of your HVAC system! This insures plenty of reserve vacuum under WOT so the air coming out of your vents don't switch to the floor or the defrost.

 

[85powerram]

Thanks for the info!

 

[Docwagon1776]

Vacuum reservoir.