Hello,

This probably has been discussed before but I couldn't get the search results exactly what I was looking for. I just bought a 1979 RX-7 with a seized motor. Previous owner ran it without oil . I sourced another motor from a wrecker but it is a 12A from a '85 Rx-7. Shouldn't I be able to just drop it in? I found some info that the 12A from '85 doesn't use the thermal reactor? Would I then have to buy an '85 exhaust and would that fit in the '79 body. Or am I just better off finding an engine from a '79 - '80?

Thanks again!!

 

welcome to the board.

please keep in mind that with your expressing concern over your thermal reactor at all, i'm assuming that you plan to keep a stock exhaust system for whatever reason. personally, i wouldn't bother with any of that stuff. get a header and aftermarket exhaust and call it a day. however, i respect everyone's right to do their own thing.

i'm fairly sure the '85 engine would NOT have the provision to retain a functional thermal reactor. so your choices would to wait until you can find a good engine to fit your exhaust/emissions system ...

OR

... just swap over the stock exhaust from an FB.

the engine bolts in just fine.

 

Thanks! I wasn't sure if I could lose the thermal reactor or not. The exhaust system needs to be replaced so I would be getting aftermarket any ways. So if I lose the reactor and by an exhaust header I would then have to buy an exhaust system that fits an '85 Rx-7.

 

honestly, as long as your exhaust system is not going to be using any of the OEM pipes, then it doesn't matter much what "year" system you buy. so a system designed for an '85 should be fine.

 

Well I finally got the '85 motor put in and all hooked up. I got it started but doesn't quite sound right. It currently has an open header as I don't have an exhaust for it yet. Here is what it sounds like.



Any thing you guys can detect that might be wrong?

Thanks!!

 

The engine if original and never rebuilt could be going on thirty years. The likelihood of an engine working out of a salvage yard is slim. Best to buy one and then have it taken apart and rebuilt by a reputable shop using new seals, gaskets etc.
Then put a header and hi flow exhaust system on the car. The difference is night and day.








.

 

Here is what it sounds like after it warmed up and ran for a bit.

 

sounds fine to me. are those old or previously flooded plugs?

 

They were brand new and the car has only run on them maybe 30 minutes total. I did run some MMO through the motor with them in it. Is the fire coming from the header normal? In that last video it was still choked.

 

i asked about the plugs mainly because of the first video. at one point, it just sounded like the chambers were flooded and needed clearing out. maybe it was the MMO. the engine sounds fine in the second video - at least, i don't hear anything amiss.

yes. the fire is normal that close to the engine. congrats on a good job.

 

Thanks! It was a project for sure. There were a few things I was not anticipating when I did the swap. The wiring harness for example. I have removed the emissions stuff (rats nest) and had to rewire the distributor to the '79 harness. I still have to get it to idle off choke though.. or perhaps I have not let it warm up enough for that to happen. Oh and the starter needed to be changed for an '85. The '79 worked but it was slooow to turn over due to the less amount of teeth.

I observed the fuel being drawn into the primaries and it wasn't a mist. It was more of a dribble. Shouldn't it be more of a spray?

 

go ahead and check for vacuum leaks before touching any of the adjustments on the carburetor. if you find none, then start adjusting the carburetor. it may also help with the amount of fuel you see coming out the primaries. if adjusting it fails to get it to idle without the choke, then take a closer look at the carburetor (cleaning, maybe consider rebuilding, etc.)

confirm timing (not distributor position, just the adjustment) and fine tune as necessary.

by the way, good job on a clean engine bay, too. really nice.

 

Will do! I painted the engine bay while the motor was out. That color is the original Sonic Bronze Metallic for that car. Eventually the rest of the car will match. Not too high on the list currently though. Thanks for all the input!

 

I took the top of the carb off and cleaned everything out. The car now holds an idle. It's a little rough but it holds an idle. It runs really rough when the choke is fully engaged too. With the choke off and driving the car it runs fantastic. Good power and smooth. I guess the idle/low speed circuit is still dirty? Here is a video of the stumble at idle.