The state of California allows you to swap a wide assortment of engines into your car or truck, as long as the engine is the same year or newer than the chassis, and all of it's emission controls are intact. Problem areas could be a heavy duty vs. light duty truck engine swap, or a CA vs. federal engine swap. Also, I don't believe it's permissible to downgrade from fuel injection to a carburetor, or from a feedback fuel system back to a mechanical one. To play it safe, you'll want to pick up and read the state's engine swap pamphlet (available from the Bureau of Auto Repair), and ask a question or two of the smog referee before getting too far along. Most CA Consumer Assistance Centers (smog referees) are located in a community college, and you should be able to stop by, without an appointment, for some quick advice.
In my case, I swapped a CA 1989 Lincoln MK-7 V-8 engine (same as a Mustang 5.0 HO) into a CA 1983 RX-7. Early Mustang 5.0 engines and all MK-7 5.0 engines are of the speed density type (a MAP sensor is used to calculate airflow), while later ones have a MAF (mass airflow) sensor. The MAF system is more compatible with engine modifications, and can be retrofitted to a speed density engine, if desired. The HO engine found in the Lincoln MK-7 and Mustang produces approximately 70 more horsepower than the stock 5.0 EFI engine, and has factory tubular steel exhaust headers, which fit the RX-7 chassis like they were made for it.
The Lincoln engine was equipped with fuel injection, electronic ignition, and the following emission controls: PCV, air injection, EVAP, EGR, and all related components, wires, and vacuum hoses. The RX-7 came equipped with a carburetor, and a considerable inventory of emissions devices, but no feedback controls. The "chassis" systems of the RX-7 that needed to be retained were the catalytic converter (or a suitable replacement) and the EVAP (charcoal canister and plumbing) system.
This part of the engine swap isn't as bad as it sounds, as most of the needed fuel system and emission controls are integrated into the engine package, with the exception of a few solenoids and relays, which mount to the body, and the catalytic converter. There are five convenient wiring harness connectors exiting the engine harness, each of which was connected to the appropriate RX-7 circuits.
Having a complete donor vehicle is by far the best way to go, as you'll have all the parts and wiring needed, plus the vacuum hose routing sticker. Don't forget to write down the VIN number of the donor vehicle, for the referee's use, and for yourself- for future engine adjustments/repairs. Also, I utilized the Lincoln's AOD four speed automatic transmission (the overdrive is nice, considering the RX-7's 3.90 rear gears), never separating it from the engine during removal or installation into the RX-7
Having kept the computer engine/transmission harness fully connected, and all solenoids and relays still attached to it, I laid this out in the Mazda engine compartment, looking for the best routing and mounting locations. I decided to mount the TAB (thermactor air bypass) and TAD (thermactor air divert) solenoids on the RX-7 firewall, along with the EEC (main system) power relay, MAP sensor, and EGR solenoid. These were lined up on the right side of the firewall, behind the windshield washer bottle. It was necessary to splice/lengthen the MAP, TAB and TAD solenoid wires about a foot, so the main wiring harness could be routed below the parts, and through the firewall (the computer needs to be mounted inside the cabin for protection). The only emission device that wasn't "self contained" on or very near the Lincoln engine was the EVAP solenoid. All that was needed here was to route a hose (the larger of the two) from the original RX-7 EVAP charcoal canister (right side of the engine compartment) to the solenoid. Now, the Lincoln computer purges the Mazda charcoal canister, as if it were its own.
That's about it for the under-hood emissions stuff! My donor vehicle didn't have a check engine (MIL) light. If it had, I would have needed to add a MIL light to the Mazda dash, and connect a couple of additional wires.
Now the catalytic converter. The referee's application manual states that the 1983 RX-7 needs an "oxidizing catalyst" (doesn't say how many). I didn't want to run the original RX-7 exhaust, as it was a tangle of heavy pipes, two catalytic converters, and a mass of rattling heat shields. Instead, I fabricated my own two-into-one Y-pipe, welded to the Lincoln's 02 sensor equipped header collectors. (J.C Whitney pre-bent 90 degree and 45 degree aluminized pipes worked great) and sent the two 2-1/4" pipes into a 3" Flowmaster collector), then fed it to a Catco (aftermarket) 3" in, 3" out TWC (three way) catalytic converter. I opted for the TWC cat, as the Lincoln engine had down-stream air injection (that needed to be utilized), and it was difficult to find a 3" oxidizing cat with the needed air inlet tube. The smog referee was OK with substituting the TWC cat for the oxidizing type, as it is superior in emissions performance, and matched the type the Lincoln originally came with. Further downstream is a Flowmaster 3" in, dual 2-1/2 out 50 series muffler. The exhaust tips look like the original RX-7's, but it definitely doesn't sound like a rotary (more like a big-block Chevy). I should add that I retained some of the Mazda floor heat shields, and fabricated additional ones in the needed locations to help keep things cool.
After completing the engine swap, I made an appointment with the state (smog) referee. He was a friendly gent, and was pleased that I had the Lincoln VIN number, and the smog devices neatly organized. After a visual inspection, he ran the car on the smog machine (very clean numbers), and performed a functional test of the EGR system, ignition timing, and fuel tank cap (they all passed). I then received the coveted door jamb sticker, and after paying $38.25 ($30-inspection, $8.25-smog certificate), I was on my way. Next time I need a smog inspection, I can take it anywhere, thanks to the attached BAR label.