I have a 86 trans am with a carbureted 305. The car sat for 8 years and the engine is just rusted out and not salvageable. Iv been checking local yards and I found a 92 roadmaster with a 350 TBI in it for $160. All the search results I can find for a engine swap are TBI to carb not carb to tbi. What do I need out of the Buick for it to work in my trans am?

 

Welcome aboard thirdgen.org.

You will need all of the harness and ECM stuff. All sensors. You'll need to do something about fuel delivery, because your '86 (most likely) has a mechanical fuel pump on the engine only, while TBI has an electric fuel pump in the tank. Shouldn't be a big deal to get an EFI tank et al from a later 3rd gen.

One issue is the '92 will have the VSS on the transmission and electronic speedometer, while your '86 has a cable drive speedometer with the VSS on the speedometer. Not too big of a deal, but some rewiring will be required. The '92 has an improved version of the TH700R-4, so you may want to consider getting the transmission along with the engine. That will change the speedometer situation, but just changing the output shaft drive gear and tailshaft housing from your '86 will get you back to the situation I started off this paragraph with (and the rest of the '92 tranny would be superior to the '86 tranny).

 

Thanks five7kid your a great help. I pulled the engine out of the roadmaster today with very little trouble. I have the ecm along with all the sensors and all the wire harnesses I need. The transmission I didn't take being I plan on installing a manual transmission when I find one. What rewiring would have to be done for the older TH700r-4 for it the work the speedo?

 

If you keep the '86 transmission, then you don't have to do anything. I was referring to the TBI PCM and harness. In '92, the VSS came from the transmission. In '86, it came from the speedometer (I may be a little over my head here, because I'm not sure when Firebirds went to the electronic speedometer - if '86, then you don't have to rewire anything).

 

Not trying to hijack Jeremies thread, but I am working on a similar swap. I found that I have 2 wires at the firewall near the relays by the brake booster that didnt match up to the original setup. Both were cut from the donor car and according to Haynes, they appear to be part of the fuel pump circuit. One is a heavy 10-12 gauge orange wire that looks like on the diagram should go to the fuel pump. There appears to be no place to connect this wire. I'm confused about where to connect it. The original engine had an electric pump in the tank so I thought everything would connect exactly the same. Not so!

The other is a smaller 16 gauge orange wire that goes to the fuel pump prime circuit. Again, no place to connect this wire. I can post some pix of the situation. I'm guessing Jeremy is going to run into something similar.