I am getting some heads from my friend and I wanted to know what a heat riser is? From what I have gathered the heads dont have them and I think I need them to pass the polution tests here in Arizona. Thanks

 

There is an old "heat riser" valve. It shut down the exhaust from one side of the exhaust, and recirculated it through the intake manifold. This heated the intake charge and warmed the air for better fuel atomization. If you are runnung a TPI, this is not needed for anything. You can block it off (in the heads), unless you need it for the EGR valve. GM actually sells a spacer to remove the "heat riser valve" from the exhaust altogether.

 

The emissions-legal heads have "heat riser" passages drilled into them - which means there's a hole on the intake side that intersects with the center exhaust passages. This is used for EGR, an emissions-control device.

If the heads don't have the heat riser hole you may be able to drill it, or use an intake base that accepts Corvette-style EGR that's fed from the exhaust manifolds.