I found this picture on chevy thunder. The problem(s) with my 1985 IROC Z 305 TPI are

1. I dont have two cats, I only have one off of an 82 camaro. The car was bought with a streight pipe. Do I need two cats?


2. My emissions has been gutted by the previous owner(even the o2 sensor!!!!) I peiced it back together but I am missing the hose routing for the smog pump. I have that black snokle thing that connects to the smog pump, and the black cannister that mounts with the snorkle, and connects with a small hose.(bypass to atmosphere?) I welded egr ports on my headers.


3. I dont have a hose that connects to the exhaust after the cat. Do i need this on my car??


How does the exhaust routed into the engine?


I know its a lot of questions, thanks

 

Dual cats only came on some 89-92 TPI engines. Your 85 came with one cat so you only need one cat.

There is a metal pipe that connects the air pump to the converter solenoids. From those two, one rubber hose goes to the passenger side exhaust, and a longer hose from there goes around the back of the engine to the driver side exhaust. The second hose from the converter solenoids goes to a rubber hose that joins to the metal pipe that goes under the car to the catalytic converter. Yes you need all of these to pass an emissions test.

On a stock engine, there is a hole in one of the exhaust ports in the head that routes exhaust gasses to the EGR valve under the plenum. When the EGR solenoid commands the EGR valve to open, the gasses travel up the tube on the passenger side runners and to the front of the plenum. The gasses enter the incoming air stream from those two "bumps" just inside the plenum at the throttle body opening.