Having looked at the high HC, CO and NO numbers on the last smog test two years ago I decided to replace the catalytic converter on a 1986 Alfa Romeo Spider Veloce (see Motorphile 2016/02/24) before taking it in for a biennial test. As the unit was clearly rattling when shaken I figured it was time to replace. Now there are so called “49 State” catalytic converters and then there are the 50 State or CARB cats that are legal for use in California. Often the California legal catalytic converter can cost about double the price of the 49 State model for the same car. Forget about trying to save money if you live in California by buying the cheaper 49 state model. First, the California Air Resources Board (CARB) requires that all legal California model cats be
stamped “D-193-88″ which is the State Executive Order (EO) mandating the higher performance converters. They will also have a unit number, manufacturing date and arrow indicating air flow. If the converter does not have these large (5”) stamps on the bottom it is not legal in California and can lead to an immediate Fail on the smog test. In addition, the CARB cat is more expensive because it uses more precious metals to achieve lower emissions levels. You could spend money on a 49 state model and possibly still fail the California test. In any case, it is illegal to sell 49 State cats in California. If you are thinking of getting around this on Ebay or Amazon – legit dealers will not ship 49 State catalytic converters to California.
Now for the Alfa the catalytic converter comes as one piece with the downpipes from the manifold included. It bolts on at the back to the pipe to the muffler. This means you need gaskets for both ends. The manifold-downpipe connection is easy to reach from the top of the car with hood open. I would undo this first and then tackle the hangers and the connection to the tail pipe. If you do not have a lift you can still do the operation of replacing the catalytic converter pretty easily. Jack up the car and place a support under the old pipe so it does not come crashing down.
Another component key in the smog system and test is the oxygen sensor. This is a Bosch unit and is located on the pipe in front of the catalytic converter unit. A faulty oxygen sensor can produce high CO readings and lead to failure. Now is a good time to replace this also – although oxygen sensors can be pricey. You need to undo the connection to the sensor in the engine compartment before you drop the old catalytic converter. Use a thread dressing that will not effect the sensor reading.
Once everything is loose you can lower the old unit out of the car. Place the new oxygen sensor in the holder on the catalytic converter and raise it into place. Things should fit pretty easily. I used a Magnaflow CARB unit and it fit just fine.
Now came the big test. I made sure I had fresh high octane gas, an oil change and that the car was running well. All vacuum hoses and other connections were tight. I ran the car fast on the freeway and made sure the catalytic converter was nice and hot. The test could not have gone better – below is the report. HC, CO and NO were down to infinitesimal amounts and the Alfa passed with flying colors.