When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Here lies the start of the build thread for my 84 FB. I have two 12A motors. The original one in my room(pictured), and a lower mileage 12A in the car.
I've been told the 12A in the car lost some but not all compression on 1/6 faces due to corner seal going out.
My goal: Tear both motors fully down. Find best rotors/housings, then evaluate what kit will be best for seals/extras.
I have attached 4 photos, each of the 4 side profiles of the original 12A.
I have 3 main questions that I need to figure out.
1) Does anyone notice anything super out of the ordinary from the photos? Any missing parts besides Flywheel, Carb, something not pictured?
2) I believe I understand all tools I need, besides:
- Punch Kit (not sure best one/different size specs that are necessary)
- 2/3 prong puller? My flywheel is already off but am quite confused exactly what kind of puller to get for when I pull the other motor, and if this is a necessary tool.
You don't need a puller unless you have to remove the pilot bearing. The bread trick will alos work. Most of the time you don't need to remove the pilot bearing.
The flywheel does not require a puller, but you will need a 54mm (2 1/8") and an impact gun or a long breakover bar. I suggest the impact. The nut nees 300 ft lbs or torque. You will also need a flywheel stop if using a breakover bar. Loosen the front e-shaft bolt BEFORE taking off the flywheel.
The HF stand will work fine to hold the 12A or 13B.
Last edited by KansasCityREPU; Nov 20, 2025 at 02:48 PM.
You don't need a puller unless you remove the have to remove the pilot bearing. The bread trick will alos work. Most of the time you don't need to remove the pilot bearing.
The flywheel does not require a puller, but you will need a 54mm (2 1/8") and an impact gun or a long breakover bar. I suggest the impact. The nut nees 300 ft lbs or torque. You will also need a flywheel stop if using a breakover bar. Loosen the front e-shaft bolt BEFORE taking off the flywheel.
The HF stand will work fine to hold the 12A or 13B.
Okay great, thank you for this info. I will keep this in mind when pulling my other 12A. Also great news on the stand, I will be picking that and many other things up today.
I've always used a 5 gallon plastic pail for building rotary engines. Engine stands are great for piston engines, but you're not working from a block with a rotary... just stacking plates.
I've always used a 5 gallon plastic pail for building rotary engines. Engine stands are great for piston engines, but you're not working from a block with a rotary... just stacking plates.
Thanks for your 2 cents here. I am going to return the engine stand as I now see that rotaries are mainly assembled/disassembled on a flat surface, so the engine stand + getting an adapter does not really seem necessary or worth it at all.
Do you have a rotary engine adapter for the engine stand?
I do not have an adapter. After checking out what Qingdao said and looking online, I will be returning the stand and will just work on plastics/the floor since it does not seem necessary.
I'm glad you started a build thread. It's great for people to track or pitch in, and personally I love reflecting back on my own builds down the road with "what did i do exactly". It's like a live diary.
I would say you can never get things too clean, so put in the effort now and it'll pay later so you don't have regrets. Do you have access to a pressure washer? That can make quick work of the gunk.
I'm glad you started a build thread. It's great for people to track or pitch in, and personally I love reflecting back on my own builds down the road with "what did i do exactly". It's like a live diary.
I would say you can never get things too clean, so put in the effort now and it'll pay later so you don't have regrets. Do you have access to a pressure washer? That can make quick work of the gunk.
Kyle, thanks for the reply. I am excited to track my journey as well.
I could borrow a friend's pressure washer, but this motor is 5 flights of stairs up from where I could use it. I will clean this one with brushes / simple green / brake cleaner the best I can before disassembly tomorrow. I will mix and match the best housings/rotors/plates between the 2 when they are both fully disassembled.
Does anyone have a certain brand or kit you recommend when choosing what seal kit to go for on a 12a?
I'm sure this is listed on the forum but would love to get some opinions.
I am planning to start the car within the week and am planning to do:
- Fresh Gas ( If old gas doesn't smell too bad I won't remove/clean tank. Or should I? Car has not ran in 3.5 years) ( 93 + 1 oz per gallon 2 c cycle )
- Fresh fuel filter
- Spark Plugs
- New Battery
- Fresh Coolant ( will check for water pump inlet rust )
- Rotate by hand check ( will turn crank pulley with ratchet and feel for 3 pulses per revolution )
- Ignition coils + wires inspection
- Mice nest check ( under carb, airbox, intake manifold)
- Carb ( previous owner said it had been gone through and rebuilt freshly as an $800 setup. Anything I should check on the carb? )
Is this diagnostic startup even necessary/recommended? I assume it would be but I am really not sure what to look/listen for, or how long to run it with a half blown corner seal on 1 rotor. It seems especially counterintuitive if I need to do a fresh oil change on it before draining it all anyways to tear it down.
I'm glad you started a build thread. It's great for people to track or pitch in, and personally I love reflecting back on my own builds down the road with "what did i do exactly". It's like a live diary.
I would say you can never get things too clean, so put in the effort now and it'll pay later so you don't have regrets. Do you have access to a pressure washer? That can make quick work of the gunk.
LOL I'm scared to look up my "old" build threads.
With two engines there you're destine to get one good one.
Stuck a flathead in the spark plug hole. (Trailing). Flathead tip BROKE INSIDE!!!. STILL rotated a bit, then locked up the rotation. 1/2 inch breaker bar with leverage and 2 dudes we got it loose finally. Excited to continue the teardown. Any advice for organization or next steps is really appreciated.
Looking to go Bridgeport. Is Mazdatrix template the move??
Keep in mind the tradeoffs you make with going with a bridgeport. You will have a higher idle, worse fuel consumption and driveability will suffer. Getting the tuning dialed in can be a little finicky depending on how you end up fueling it too. I'm not trying to dissuade you, just inform you of the tradeoffs that the braps and power will bring. I think many people feel like a large street port template gives you the best of all worlds with better driving characteristics especially if this is going to be a street car.
well, this rebuild just got more expensive. possibly damaged rotor AND housing. may even scratched the plate.
I'm hoping not, but I know you might be right. Thankfully this is the donor engine so I'm mainly just practicing tear down on this one before I tear the one inside the car down which most likely has better condition components.
What can you suggest for me when I need to break this bolt on the other more important motor? I assume I will just want to do it before I break the flywheel nut loose, right? The previous owner had already taken the flywheel now so I figured jamming a screwdriver was the best way here lol.
Did you use that screwdriver to give leverage to get the e-shaft bolt out?
Yes I did. It seems like it sort of worked. I am about to just take the rest of the motor apart to see what damages were done. But can you suggest a better way for my second motor?
Keep in mind the tradeoffs you make with going with a bridgeport. You will have a higher idle, worse fuel consumption and driveability will suffer. Getting the tuning dialed in can be a little finicky depending on how you end up fueling it too. I'm not trying to dissuade you, just inform you of the tradeoffs that the braps and power will bring. I think many people feel like a large street port template gives you the best of all worlds with better driving characteristics especially if this is going to be a street car.
Okay, thank you for your advice. Can you recommend an exact template for a mild street port then? Also with just a mild street port like you are talking about, is a full exhaust necessary with headers or can I keep anything stock?
Install a flywheel stop then loosen the front bolt, then remove the flywheel nut.
Ask me how I know. I damaged my first take-apart engine rotor housing by not removing the front bolt first. I didn't use a screwdriver or put anything in the chamber but the result is similar to yours. Dented the housing just enough so it was not usable.
Install a flywheel stop then loosen the front bolt, then remove the flywheel nut.
Ask me how I know. I damaged my first take-apart engine rotor housing by not removing the front bolt first. I didn't use a screwdriver or put anything in the chamber but the result is similar to yours. Dented the housing just enough so it was not usable.
Gotcha, I will learn how to install the flywheel stop on my second motor to get that front bolt.
I am hoping mine will still be usable. The engine stayed binded while the tip broke off I believe. We will see later today when I take the rest apart. I will post photos and keep you updated.
Between the 4 housings I have, hopefully I can get 2 solid ones.
Question for you: What would be the best tool to buy or method for me to pull the stationary gears at home? I'm having a lot of trouble prying them out. I assume I want to remove them to clean and re grease? Or should I maybe just leave them pressed in?
The stationary gears are held in with bolts around the outside of the stationary bearing housing. The gears themselves are part of the cast stationary gear assembly. The bearings are pressed in.
The front and rear stat gears do not have to come off the iron, not yet at least. You can take the engine apart with these still on the irons as long as they haven't welded themselves to the e-shaft with loose of oil and heat. Once the bolts are out, you can use a rubber dead blow from the inside out if they are stuck.
Before going too far, post a picture before doing anything so we are all level set on what you're doing.
The stationary gears are held in with bolts around the outside of the stationary bearing housing. The gears themselves are part of the cast stationary gear assembly. The bearings are pressed in.
The front and rear stat gears do not have to come off the iron, not yet at least. You can take the engine apart with these still on the irons as long as they haven't welded themselves to the e-shaft with loose of oil and heat. Once the bolts are out, you can use a rubber dead blow from the inside out if they are stuck.
Before going too far, post a picture before doing anything so we are all level set on what you're doing.
Gotcha thanks for the knowledge. The first three photos are the iron we are currently trying to get off. It is really just stuck on there. Then there's also a photo of the backside of the motor which I am choosing not to open right now since I cannot get that stationary gear off which looks like it would be mandatory to get off before pulling the back side. Maybe I'm wrong on that though, let me know.
You can see we are using a rubber mallet but maybe we just need to get a bigger one? Mainly hitting it against that point where it is shown in the photo. Thanks for the help
1984 FB Tasteful Restoration
