upgrade to O2 and 3 way cat

[aantipas]

I own a '79 911SC with backdate exhaust and smog pump system removed. The original engine blew and the current engine is out of a 1980 SC. However, the CIS is off the 1979 engine.

I'm moving to California and need to reinstall the original exhaust system with two way catalyst and smog pump. I'm wondering if it would be easier to upgrade the CiS (ECU?) to the 1980 specification with an O2 sensor and 3 way catalyst vs. re-installing the smog pump set-up?

How will this be viewed by the California air board?

Other thoughts or recommendations?

Thank you,

Andy

[IslandHopper]

Welcome to the horrible world of the CARB... The technical answer is, your car needsto have everything correct for the model year, as in 1979, to pass the actual inspection, regardless of if it will pass smog or not. That being said, the chances that the kid at the local smog station know and/or will take the time to research and properly evaluate that part of it are probably on your side. Unfortunately, much of it is up to who does the smog. This is of course, assuming the car can actually pass the actual smog test in either 79 or 80 arrangement. The smog requirements will be based off of the 1979 model of the vin, and it will be an actual run and sniff (OBD2 cars can now be smogged with a handheld scanner!) so hopefully it will and you are mostly there.
California absolutely sucks for old cars that need to be smogged, especially anything modified. The one thing you have on your side is that the car is really old by most standards, and most people nowadays won't have any idea what is or is not supposed to be on the car for the visual inspection, in most cases you just need to make sure it all "looks" like it came from the factory that way, and that it actually will pass the sniff test.
Long story short, nobody will know your engine is from 1980, and your car will be judged as a 1979. Assuming it passes the smog test ithat it should, you will be fine.

[aantipas]

Island hopper thank you for the response. I'm assuming that means I need to have the smog pump in place for the visual and not just the cat and )2 sensor? Thanks, Andy