[rfmaster]

Originally Posted by irongun324

Ok Update.


As for the EGR valve...

http://67-72chevytrucks.com/gallery/...0/P1040992.JPG

You can see 2 ports on the left, one on the right (What exactly is this part?). The right goes to the TB, left (at least the one that's connected) to the EGR Valve. I have zero vacuum on egr side, but I am getting good vacuum to the throttle body.

Here is the overall look.

http://67-72chevytrucks.com/gallery/...0/P1040993.JPG

That is what is known as EGR vacuum solenoid (there are other names) - it is controlled by ECM. ECM pulse width modulates (PWM) ON-OFF amount of vacuum applied to EGR valve. When this valve is OFF the EGR connected side is vented to atmosphere (so that vacuum is removed from EGR valve diaphragm). In normal operation this valve is vibrating - ON -OFF determines how much vacuum is being applied to EGR valve. Expensive to replace when they go bad.

//RF