Rx-7 engine swap

[Waffles]

I've got an 85 RX-7 that was my first real car. It's been beaten and broken over the years. I always swear I'm going to resurrect it into a 450hp rotary(possible), I just don't have that kinda money.

Still wanting to resurrect it in some fashion, and knowing I wouldn't be satisfied with the 101hp stock engine (140 or so with current mods) I started thinking about doing a V-8 swap. I've seen a few FD V-8 swaps (Kevin Doe) but not many done on FB cars (1st gen).

So, I'm trying to decide on a powerplant for the swap. Most people opt of GM plants on these swaps, and while I'm not entirely opposed to that (I even posted a similar thread on NKYFBA) but there are 2 reasons I want to go Ford. #1 because I'm more of a Ford guy and #2 because most people go with GM ;)

So, my first thought was to pick up a 4.6 from a Mark 8 but it turns out the DOHC, and even the SOHC motors are too wide for the engine bay. I then happened across a 3.8L T-bird supercoupe for cheap, but it looks like 300hp is on the extreme end of power. While researching I found that people were taking the Eaton M90 superchargers from the Supercoupes and putting them on their 5.0 fox body cars.

NOW my wheels are really turning. I'd be happy in the 300-400 range. Wondering if anyone knows how hard it would be to mate a M90 to a 5.0, and how expensive it would be to get a 5.0 in that power range. All feedback is greatly appreciated.

[PaulFiveOh]

I almost bought a FB 5.0 swap.
He used to work at the oil change place off 28 (almost) in Old Milford.

Not sure if he is on here, but if he is, that would kick ass for ya.

[Goober]

http://www.grannysspeedshop.com/

[Rick93coupe]

I've never heard of anyone putting one eaton on a 5.0, but I think I have a link to a guy who put 2 on. One doesn't seem like it would support the extra cubes.

[Da Natti]

The stock eaton M90 will support up to 5.0L of displacement!

[Rick93coupe]

All I'm saying is do the research, I doubt it will support enough power to make it worth the hassle. Better yet, just show me it works well!:bigthumb:

[Waffles]

All Ford Mustangs (http://www.allfordmustangs.com/forums/mustang-tech/2812-supercoupe-m-90-on-302-a.html) forum link about adding the M90 to a 5.0

I don't know if it would work, but I'm definately interested in finding out.

[Waffles]

http://webpages.eng.wayne.edu/~al0769/306/m90power2.jpg

http://webpages.eng.wayne.edu/~al0769/webpics/april15_front.jpg

http://webpages.eng.wayne.edu/~al0769/webpics/april15_passenger.jpg

This guy mentions lots of heat problems and is considering water injection to cool it down.

[Rick93coupe]

I've been researching it too. Its definitely different, but is it less costly than traditional setups? Room is also a consideration in a engine bay as small as a rx7. Good luck with whatever you do.. I'd love to have something like that myself. Kevin Doe's car is the chassis I would use.

[Goober]

My biggest concern would be the heat from that thing spinning fast enough to power a 5.0. I wouldn't use it unless you plan on running a water/meth unit.

[brncoupe5.0]

Go to, youtube .com and type in [m90 on a 5.0 mustang] watch this car run,intake and cam 12.30s on 5 lbs of boost.

[Waffles]

http://www.grannysspeedshop.com/

Wow... that's awesome. Somehow I missed this post earlier.

[Waffles]

Well, my brother gave me a 351W for this project. It came out of a late 70's F-150. Also came with a C6 trans. Engine came out of a parts truck my nephew bought, and he ended up using the 400M out of the other truck. He said they drove the truck for a week before tearing it apart and the motor ran strong.

So, I know nothing about these motors. I need some help planning things out and determining what to do with it.

The RX-7 is going to be gutted and built into a drag car.

Suggestions?

[Waffles]

How strong is the stock bottom end on these things?

[Buckeye]

The guys on buckeye stangs were talking about the newer split port 3.8 that a 03 cobra blower swap on and 300 is a starting point. Friend here in town just did a 2.3t and on stock motor and low boost made 280 something but 300-350 is fairly easy to do. That whould be my pick

[Gearhead559]

http://i5.photobucket.com/albums/y196/gearhead559/Shop%20stuff/100_3572.jpg

i have one here im doing..if you need any help, let me know

[Waffles]

Well, my plans changed a bit for the car. It was going to be a street car, but I've got my Supra and will have my Cobra too. This will be a gutted drag car. I've already got the 351 now so I think I'll stick with that. Thanks though, I think that sounds like a fun swap.

[Waffles]

http://i5.photobucket.com/albums/y196/gearhead559/Shop%20stuff/100_3572.jpg

i have one here im doing..if you need any help, let me know

Whoa... that's bad ass :) I didn't see your post, evidently I didn't refresh since last time I posted or something, odd. Anyway, did you use the stuff from Granny's or did you fab your own shit up?

[Pitbull1052]

what year Supra? I've had 3 MKIII's

[Waffles]

It's a 90 Turbo with a 5 speed and Targa. I had absolutely no plans to do anything but drive it. Then the head gasket started leaking so I pulled the head and went with an HKS MHG and ARP headstuds. Then all the rubber and plastic needed to be replaced because 20 year old stuff seems to disentigrate when you mess with it. So I did intercooler, IC piping, and changed all the vac and fuel lines. I replaced the radiator with a 3" aluminum unit. Also did 3 inch stainless exhaust and shimmed the wastegate. Still needs some things buttoned up. Swaping to the Lexus AFM and bumping to 550cc injectors and fuel pump next I guess. It's a fun car. What'd you do to yours?

[Gearhead559]

Whoa... that's bad ass :) I didn't see your post, evidently I didn't refresh since last time I posted or something, odd. Anyway, did you use the stuff from Granny's or did you fab your own shit up?

this has a grannys kit in it. but custom mounting a radiator in it. and the grannys stuff looks like it could be copied rather easy. those pics are the condition i got the car in from the customer. i have the task of wiring, and replumbing every thing in the car.

been working on laying out the wiring the way i want it, for a test fire. before the supercharger goes on.

[1_slo_92]

It's a 90 Turbo with a 5 speed and Targa. I had absolutely no plans to do anything but drive it. Then the head gasket started leaking so I pulled the head and went with an HKS MHG and ARP headstuds. Then all the rubber and plastic needed to be replaced because 20 year old stuff seems to disentigrate when you mess with it. So I did intercooler, IC piping, and changed all the vac and fuel lines. I replaced the radiator with a 3" aluminum unit. Also did 3 inch stainless exhaust and shimmed the wastegate. Still needs some things buttoned up. Swaping to the Lexus AFM and bumping to 550cc injectors and fuel pump next I guess. It's a fun car. What'd you do to yours?


bobsgt built a hell of a supra a few years back then i picked it up and did the body work and shipped it down the road. fun cars but a pita to keep up with imo.

[Camaro86SHOCKER]

i too have one of these in my garage if you wanna stop by and see it. Its a 91 rx7 and we have swapped the entire drivetrain from a 89 lx 5.0 5-speed into it including the t-5 and 8.8. Its a super nice car just wont clear the stock hood. Its just about done if you ever wanna stop and see it for some inspiration or questions answered. ill take pics and post later.

[Waffles]

this has a grannys kit in it. but custom mounting a radiator in it. and the grannys stuff looks like it could be copied rather easy. those pics are the condition i got the car in from the customer. i have the task of wiring, and replumbing every thing in the car.

been working on laying out the wiring the way i want it, for a test fire. before the supercharger goes on.


bobsgt built a hell of a supra a few years back then i picked it up and did the body work and shipped it down the road. fun cars but a pita to keep up with imo.

Even the die hard 7m fans will admit they're a lot of trouble. I've always loved the way the car looks. It's pretty straight, rust over the rear wheels, paint is rough. A paint and body guy I know is out of work and said he'd cut me a deal if I can swing it. I bought the car for WAY cheap. I should have just turned around and sold it lol.


i too have one of these in my garage if you wanna stop by and see it. Its a 91 rx7 and we have swapped the entire drivetrain from a 89 lx 5.0 5-speed into it including the t-5 and 8.8. Its a super nice car just wont clear the stock hood. Its just about done if you ever wanna stop and see it for some inspiration or questions answered. ill take pics and post later.

I'd love to stop by and take a look. I was wanting to use an 8.8 on mine, but read that it wouldn't work. Obviously, it did for you... so good news for me!

[Gearhead559]

85 and 91 7's are 2 completely different cars, that use different kits.

the stock intake 5.0 clears the stock hood in a 85 perfectly. now the second generation cars, not even close to clearing.