1980 RX-7, with a V8?

Yes world I am removing the rotary from my 1980 RX-7, and it was planned that way from the beginning.

A little about me.

This is going to be my first "build" I have ever done. My only previous experience with a sports/muscle cars was a 1999 Camaro Z28 I had 10 years ago. The only track time the Z28 saw was down the drag strip. But I was there almost every other Wednesday night in the summers for 2-3 years. The Z28 never saw too many mods, mostly just a programmer and chassis/suspension mods that got me to the low 13's. 8 years ago life happened (AKA a pregnant wife), and the car was sold to a friend and I bought a new 4 door truck. The past five years have been good to me, a better job, improved income and an affordable house that allows me to start a project.

What I want from a car

Driving the canyons, auto-X, drag strip and occasional hot laps around Thunder Hill are all things I want to go and do with a car. I am not interested in having a purpose built track only car, but a car I can beat on a little bit and have some fun. My budget is low, time I can spend on the car is limited, and so this maybe a slow paced build done one step at a time.

I have decided to share here on the GRM forum because I feel a lot of you have similar goals and situations as I do. I have been following the board for over a year now and have envied all of your projects. So many of you are amazingly resourceful, dedicated and knowledgeable that I will find the best advice and comradery here on the great GRM forum.

After watching an episode of Drive on NBC Sports Network and watching Matt drive the so called “No Fu#@$” RX-7, I was fastened with the idea small, lightweight V8 Japanese sports car. I had always liked the Fox body Mustangs and the Ford 5.0EFI engine, and I also knew where there was an SA RX-7 rotting away in a field. I did a little research, found Granny’s Speed Shop, and I was sold on the idea of a V8 RX-7.

The Car,

The car is a 1980 RX-7 (I believe a GS) with a manual 4spd transmission. The car sat after it failed a smog test in 2009. I reinstalled the carburetor (PO thought it was the reason for failed smog) to get it running on starting fluid. I wanted to ensure the engine would run so I could sell it and recover some of the cost. The cars body is little rough, I will have to learn some body work at some point. But the chassis and frame look good. It’s a California car so there would have been no rust had the PO not left a pile of leafs on top of the cowl, but everything else is essentially rust free. With the car also came a 1985 GSL-SE LSD rear diff and disc brakes, and the famed whale tail spoiler to be installed later.

The donor

A year went by with the Mazda just sitting in my driveway as I saved money for a donor vehicle. In August I found what looks to be a good donor. A 1993 Mustang GT w/ a T5. The body and chassis are tore up, but it does drive. The PO I purchased it from sold it to me because he couldn’t get it to pass smog and did not feel like investing any more money into this car. The engine fires up good, idles smooth and doesn’t seem to have any real leaks. I think a tune up and a fresh catalytic converter and I can get it to pass smog in the RX-7. I will worry about improving the performance down the road.

This weekend I finally got to work on the project. I have located a buyer for the 12A, so I removed it and the transmission from the RX-7. I just need to double check what all need to keep for the conversion and its will be sold with no turning back on the project.

Next step, find a few minutes during the week to call Granny’s and get the conversion kit coming.

Sorry, took me a moment to figure out how to add photos.

Here is the car the way I found it.

I got the car home and gave it bath. Looks a little better.

Awesome!

I loved the YouTube video with the RX7 you spoke of.

Good gearing and mild modifications really wake the 5.0s up. Depending on your budget, the explorer intakes and cylinder heads work well. If you are on a really tight budget, I hear good things about getting the stock lower intake manifold welded and ported.

Can't wait to see how this one turns out

I wonder how many V8 RX7s that video inspired? It certainly inspired me to put a 5.0 in an FC. My first build also. Tons of fun. Good luck with the build.

A family affair getting the 12A pulled out. The neighbor, grandpa and wife all chipped in to help me roll the hoist up the drive way.

Probably one of the easiest engine I have ever had to remove from a car.

Does anyone know if the 5.0 & T5 will go into the Seven in one shot? Or will I be forced to do it one at a time?

I placed the order with Granny's. ETA 2 weeks. I will try and get the fuel tank out next.

I like this thread. I'm in for more.

Cool and welcome!

I have always, always wanted to do this.

Thanks for all the welcoming comments. I appreciate it.

I don't have too much to update. I sold the 12A, transmission and some other stuff today. I wish I could have received more than $350 for it all. I think if I lived in another state where smog restrictions were not so strict I may been able to fetch more. It was an easy hand off though.

Only real progress on the car was removing some unneeded electrical from the engine bay and reading up on the electrical mods and connections that will have to take place.

I am still trying to find a little more time to remove the fuel tank.

The 5.0 T-5 should all go in as one piece if you have the radiator, Ac condensor etc removed. Our 79 5.0 chumpcar was a ton a fun.

Good luck with the project!

Love the concept and the 5.0 is one of the cheapest hp additions.

I unfortunately have not made much progress the last few weeks. My excuse is the usually life story, no time or bad weather. Tomorrow I am planning to remove the fuel tank.

The only progress made is I have received some parts from Granny's. I placed an order a month ago and on Monday received a couple of packages.

What I have received, engine mounts, transmission mount, engine mount brackets, transmission cross member, master cylinder and slave cylinder.

Master cylinder & pull type slave cylinder. Engine mount bracket. Made of 1/4" steel, looks pretty nice. Transmission cross brace. Also made of 1/4" steel.

I have not received some of the larger components such as the radiator w/ brackets and the driveshaft. I have emailed Granny's asking for an ETA but no response as of yet. He did state in the beginning that all orders are built to order. So for now I am patiently waiting, but there is plenty for me to do if I can make the time.

I hope to be back with another update tomorrow.

Yay another first gen build!

This is cool, I'll be following along!

Good news, I was actually able to work on the car yesterday. I removed the fuel tank and pulled the sending unit out and took a look inside. While the fuel smells horrible, there was only some small amounts of sediment and crystal material in the tank. I did not see any rust or scaling, I was very happy to see that. I need to get a bucket and drain the remaining fuel (probably less than a gallon) and I am thinking I will clean the tank out with some denatured alcohol. I went a little further and dropped down the fuel pump to see what there is to work with in regards to where I can mount the new fuel pump. The stock fuel pump is located just in front of the rear axle, under the floor board on the driver side. The pump mounts to a steel plate, and the plate mounts to the car with 3 fasteners. I like this location, it seems to be protected pretty well, and it mounts lower than the lowest spot on the tank (the inlet fuel line does curve up and over the axle housing). The OE fuel pump is pretty small however. And I am not sure if this area is large enough to support the aftermarket fuel pump I will need to run for EFI. So I could use some help at this point. I do not have a great wealth of knowledge when it comes to fabricating or customizing fuel systems. I want to make sure it is safe obviously, and keep it as inexpensive but as reliable as possible. I need some help on a few things.

1) Recommendations on a fuel pump. I am running EFI that I believe spec fuel pressure is about 39-40psi. The 5.0 is probably about 200hp, but I would like a fuel system that could handle around 300hp for future upgrades.

2) Fuel filter? Run one before and one after the pump? Any suggestions?

3) Can the OE hard fuel line handle these requirements? The fuel line is either ¼” or 5/16” (I tried to measure and had a hard time determining the size). Greg you spoke of a ’79 Chump Car build. Did you guys run EFI or carbureted? And did you run your own fuel line from the back of the car to the front?

One note that I will mention. Granny’s recommended against EFI for my year due to the lack of baffles in the fuel tank. So I plan to keep the tank above ½ tank so as not to stall when I make an aggressive turns. This will also help with the front/rear weight ratio as well.

The fuel system is the part of the build that will be the largest hurdle for me I believe. Once I get past this I will have more confidence in getting the car running.

Thanks everyone.

Ours is carburated.

If you can find a gsl-se you can get return lines. Otherwise if you find another 12A donor you could just grab another set of supply lines and use them as for the return.

I would imagine pretty much any external efi pump should work. We had build a 5.0 miata a few years back and the stock miata pump was fine. I would run a filter before the pump. Sometimes another up in the engine bay can be useful for trouble shooting.

A little bit of progress has been made over the last few weeks. I removed the front sub frame and performed the modifications to it. The mods require two hole drilled to support the new engine brackets and reverse its direction when you re-install it. While I had it out I cleaned it the best I could with Simple Green, water and a tooth brush. After it dried I gave it coat of Rust-Oleum primer and paint. Compared to the rest the car it looks pretty good.

The sub frame re-installed with the new engine brackets in place.

The kid saw dad in the engine bay and thought it would be fun to hop in herself.

In addition to the sub-frame I have cleaned the fuel tank out, bought a new valve and grommet for the tank and removed the AC evaporator.

My current trouble spot is with installation of the lower radiator support. I can’t figure out where it is supposed to go. Granny’s instruction are below.

“Installing the Lower Radiator Bracket... The 1st gen RX-7's front chassis brackets changed slightly over the years. Early cars used a radiator/oil cooler assembly, where later cars used seperate oil cooler mounting tabs located down in the chassis just in back of the front sway bar. Depending on which style your car uses, installation is as follows...

'79-'80 SA Chassis...has rectangular sheetmetal "tabs" extending inward from the frame rails, located just in back of the front sway bar. Our lower rad bracket slides over these tabs. Some cars require slight trimming of the chassis tabs for a good fit.

'81-'85 FB Chassis...has oil cooler brackets extending upward from the chassis, with each bracket having a horizontal flat pad on top that has (2) holes. Our lower rad bracket for this chassis simply lowers onto/attaches to these pads, placing the lower part of the radiator mid-way between the RX-7's round front crossmember and it's front swaybar.”

Now my car is 1980 SA model. So behind the swaybar somewhere there is supposed to be a “sheet metal tab”

Here is picture of my engine bay looking forward. The sway bar is between the circular cross bar and the sub frame. I do not see these sheet metal tabs.

As a note, my oil cooler for the 12A was mounted as an assembly with the radiator (2 rubber mounts that bolted itself to the radiator)

There is only one place in the engine bay that the radiator support can even span the distance, and that is on a heavily reinforced sheet metal and steel bracket just in front of the sway bar. This area supports the radius arm and swaybar. It does not seem like a logical area to trim, nor does it have a flat area to mount it to. Here is a photo of the area I am referring to with the lower radiator bracket resting in top of it.

My wife calls me blind all the time, maybe one of you can spot what I am missing. My current thought is one of two things. I was sent the wrong bracket or my car is a weird production range and missing these sheet metal tabs. I have emailed Granny’s for some clarification a couple of weeks ago, but have had no response as of yet (it has been the holidays so I am being understanding of that). Any suggestions would be welcomed.

Is it possible they were removed at some point?

Would the bolt shown here fit through the support?

I got a response from Granny's yesterday. Like I had been thinking there were supposedly some vehicle that came with neither of the two listed mounting tab styles. He is sending me tabs I can use to mount the radiator support to the car. He says it will require some drilling. I'll let you know what turns out.

Looks good man! I will keep up with this one! I wanted to get a FB for my swap when I started thinking about it but ended up with the FC because of the rack and pinion as well as the IRS. But the FB is so light! Hope the parts from granny speed fit well, I had issues with there fitment in my car. But they are really good with customer service and if you give when a call with any questions during the swap they will be more then happy to help. Also racing beat are helpful for specific questions.

Skervey wrote: Looks good man! I will keep up with this one! I wanted to get a FB for my swap when I started thinking about it but ended up with the FC because of the rack and pinion as well as the IRS. But the FB is so light! Hope the parts from granny speed fit well, I had issues with there fitment in my car. But they are really good with customer service and if you give when a call with any questions during the swap they will be more then happy to help. Also racing beat are helpful for specific questions.

Thanks Skervey. I like the idea of rack and pinion steering as well. I have seen some people make modifications to add a steering rack from another car fit. I can't say I have put this on my list of things to do at this point. I guess I kind of like the idea of having my hands full with the challenge of the conventional steering.

A quick update on the project. Last weekend I was able to spend a day cleaning up a few odds and end on the car in preparation for the 5.0.

Yesterday I began the removal of the 5.0 from the Mustang.

Before I did that, I thought it would be a good idea to get compression reading from the engine. The PO stated it did smoked a little out the tailpipe on WOT. When I pulled the plugs 4 & 8 told the story of this, especially in #8. I could see a buildup of oil residue on the plug.

As I took the compression things were looking pretty good. Cylinders 1-7 were all at 115-120PSI (I don’t know the spec but they were nice and even), but then I came across cylinder 8. Cylinder 8 had half of the other cylinders, 55Psi. Ouch.

I moved forward with taking the engine out. The coolant drained did not look so green, but it was clean. I did not test the specific gravity to know if it was strait water or a lighter colored antifreeze. Tomorrow I will finish removing the engine. All that is left is the exhaust, mounts, fuel lines, drive shaft and shifter.

The condition of the engine is not what I was hoping for. My original plan was to go back later and rebuild the engine and install GT40 heads and intake form an explorer. With these compression reading I am now contemplating doing a stock rebuild before installing into the 7. The PO had trouble passing an emission test for high HC. The car idled and ran so good I figured a fresh O2 sensor and catalytic converters and I would be able to pass smog. The low compression on this cylinder is likely contributing to the high HC’s, and I am now questioning whether I can pass smog with the current condition of the engine. Rebuilding the engine now will defiantly delay progress of the build.

I am open ears if you have any thoughts on whether I should go with it or re-build it.