Congedom

Alrighty so here is some backstory - I am in an Auto Tech school and had to rebuild a motor last semester which was a 1987 JDM 13b NA engine. Just yesterday, I bought a 1979 Rx7 (with the 5 speed) with a bad 12a and was looking to swap the 13b in but had a few clarifying questions before I mass buy parts and dig in.
Here is what I have:
- 1979 RX7 w/ 5 speed
- Car has full header back Racing Beat exhaust setup
- 12a with everything still on it
- 12a has a Racing Beat Oil pressure sensor on it that wires back to a gauge in the car
- 12a has a dual pulley alternator setup that I believe is not stock.
- JDM 13b out of an 87 NA car w/ the flywheel still on it
- Newish Oil cooler and lines that came with the engine
- Wiring harness for the 13b (No ECU or anything)
Here is what I think I know:
- Use the front cover off of the 12a for mounting all the goodies
- Need a 84/85 GSL-SE oil pan
- Front engine mount needs to be slotted or buy the swap part from Racing Beat

With these things above, everything should mount up and sit good in the car. Please correct me if I'm wrong on any of this. My reason for making this post was to ask about Fuel and Exhaust systems and how that will play into this. The car already has a full Racing Beat exhaust setup on it so if I get the Racing Beat manifold for the 13b will that plug and play nice or do I need to go stock and do some welding to get that to fit? And fuel would be my last concern (that I know of). I could do and EFI setup but am not familiar with haltech systems so I was leaning towards the Carb route. From my understanding, doing this requires either the plugging of the injector holes or using the centerplate out of the 12a and adding a carb setup. Should I go with the Holley kit on Racing Beat or are there other (cheaper) options out there that will not negatively impact performance? As well, I probably would need a new fuel tank/pump setup but don't know where to start on that. Any wisdom y'all can impart would be greatly appreciated. Thanks!

KansasCityREPU

iTrader: (9)

This is not a complete list.

1. You will need to drop the tank and clean it.
2. Add a slosh cup to prevent fuel starvation.
3. Increase the size of the fuel supply and return lines.
4. Add a fuel pump that can handle injectors.
5 Replace all fuel soft lines.
5. Find a factory engine CPU.
6. I'f add a second gen fuse block on the drivers strut tower for the additional fuses needed.
7. I'd also replace the rad with a taller on then came in the 1979.
8. You can use the 1979 front mount oil cooler or go with the send gen one. Will need custom mounts.
9. Get a 225mm clutch. The 1979 is a 215mm and will work but just get new. General rule is to match the flywheel.

*** OR ***
Go carbed and not have to do most of the things above. Cleaning the tank is a must.

Congedom

Thanks for the info! I just asked the seller what size the clutch was since he replaced it less than a year ago. I was digging around my garage and found a new radiator I haven't used yet but may have to check clearance as it might be too big for the car or just mess with oil cooler/radiator locations if needed. Do you by chance know specifics of if the fuel pump is internal or external on the 79 and what size would work for feeding the 13b? For carbed engines I know low psi (maybe 6psi?) but dont know how much fuel is needed in that respect.

KansasCityREPU

iTrader: (9)

All first gen RX-7's have external fuel pumps. You want 8mm (5/16) for the supply. I think 6mm for return. These are also the same sizes for the fuel soft lines.

I think all 1979-1982 clutch disc are 215mm. 1983-1992 are 225mm. You want 225mm to match the engine flywheel.
https://mazdatrix.com/product-category/clutch-flywheel/

For the oil cooler, convert to -10AN and nylon braided line.

j_tso

iTrader: (2)

Letting you know ahead of time in case you think it doesn't fit, we recently found out the stock motor mount shell needs to be trimmed to fit with the Racing Beat bracket.
Thread link
The metal on the mount is thin and easier to cut than the bracket, depending on what tools you have that may be easier than slotting the bracket.

Congedom

Thanks everyone for the replies! I’ve done some more research and think I’ve got most of what I need. If anyone else has anything to add feel free to let me know if I should consider something!

Congedom

Hey yall, quick questions, so I've done some research (and funding) and am placing orders for parts as I type this. I saw on a few threads that you CAN'T put the 12a center iron between my 87' (s4?) 13b rotor housings because of the coolant grooves being on 13b irons and 12a rotor housings? I am going with a carb setup for "simplicity" so am I just going to need to use the 13b center iron and plug the injector holes instead? I already planned on using the 12a front cover so that is all still good and will bolt up to the 87 rotor housing yeah?

j_tso

iTrader: (2)

Yep, plug the injector holes on the 13B engine to run a carb.
12A front cover will bolt to the later engine.

85 and earlier irons and housings will not work with 86 and later irons and housings.
-85 iron is on the left and 86+ iron on the right with the coolant seal groove.

KansasCityREPU

iTrader: (9)

Yes - just plug the injector holes and use the 12A front cover. You will also need a GSL-SE or older 13B oil pan\. So 1985 or older 13B oil pan.

kurtf

iTrader: (3)

I'm not an expert like many here that provide good advice but decided to comment as I need a break from work plus I race a SA first-gen with the NA-FC 13B core. Also like many RX7 owners, my RX7 budget has always been tight.

My first thought is that now that you have experience rebuilding a rotary and have resources available at your school, have you considered a basic rebuild of the 12a that came with the car? If the core is adequate that may get you on the road quickest and you could find out if there are any other issues with the car.

I totally understand why you would want to go with the 13b however. If I was a student on a budget, my focus would be getting that motor running/driving first then worry about upgrades or making it perfect later. If you didn't port the motor, the factory fuel pump will get the engine running. I am assuming an after market carb/intake. Easy button would be the Racing Beat intake and a Weber or similar knock-off like EMPI. I would go with a IDA48 but maybe you can pick up something used that would work. I am of course assuming you do not have any emission constraints in Montana. The correct thing to do eventually would be to enlarge your fuel line, get a Carter or similar fuel pump and regulator. If you didn't port the motor, this isn't as necessary immediately depending on how you plan to drive the car.

Since you have the school resources, you could modify your existing header. From what I read here on the forum, it sounds like Racing Beat has a long lead time for their headers. My header on my EP car started out as a Stainless 12A header that we split 10mm at the flange. If the existing exhaust can system can be sucked up toward the front of the car a bit(15mm), then just cutting and rewelding a new or existing mid-pipe flange could possibly work.

Just random thoughts that don't need to be taken seriously. When writing replies like this, I always comment about the importance to get the car running. It is painful to read about all these cool projects that stall due to lack of money, time or energy. I still see guys that show up at the track without a car, telling me about their progress while their car hasn't moved under its own power in years.

Congedom

Thanks y'all for the information!
I already have on order a 48 DCOE carb kit off atkins and a bunch of other stuff coming in soon like new fuel pump/regulator, 84/85 pan and gasket, Front engine mount, gaskit kit, and a Header that *might* bolt to the existing racingbeat system on the car. Messaged RacingBeat about the exhaust compatibility and they steered me in a good direction. Worst comes to worst Ill get some welding in and try and get the system in order.
To answer @kurtf , yes I am a student in college but Im in my 20s returning to school after working for years to save up for it so while I still like to have a budget, I have a bit more wiggle room than your average college freshman I have considered rebuilding the 12a but I had the 13b prior to my RX7 purchase because my original plan was to run it in my E30 project but have since changed my mind and want to do either an LS or Honda B18 swap in that one. I already daily an FJ80 so having a non-op car isn't too bad for me plus with winter here I probably wont do much driving in RWD cars until spring. As for the 12a, it was rebuilt by the PO (should only have 200 miles on it) but he forgot some oil O rings and overtightened the rear keg bolts out of pattern so the rear rotor is struggling to spin causing misfire and other problems with the car. I figured I'd toss in the 13b and get the car running all nice and good then rebuild the 12a proper and sell that off to recoup some of my build money. I too hate to see projects sitting around but now that I have the auto garage and mentors able to help me I plan on finishing the RX7 within a few months having that ready for spring/summer and taking my time on the E30 to build it into a more high powered track or drift car with some more custom bits like suspension and drivetrain. Who knows? Maybe I'll make a "build" thread on here and inspire someone else to finish up their stuck project
Thanks again everyone for helping out my newbie bum, appreciate all of y'all giving me confidence for this lil project!