# 1975 Mazda Rotary Pickup Build Thread



## chuyler1 (Apr 10, 2006)

Hi everyone, long time member here getting back into audio. I'm in the process of a rebuild for my "REPU" and I figured you might want to follow the progress. The next few posts will be a little catching up, and in a month or so you'll start seeing some audio gear go in. Until then, enjoy the process...

First off, the truck...





































Before taking things apart, I got a quick dyno run to see where it stands. It has a few modifications from stock such as a 2.5" exhaust and racing beat header. I'll be installing a ton of performance parts over the next few months.










Although I love the exterior color, the carpet is a bit much so I'm replacing it with new black carpet and swapping the bench seat for buckets. I'll be installing a few more speakers (since it just has one in the dash), amps, probably a MiniDSP, and upgrading the motor to fuel injection, and replacing the entire wiring harness along the way.

And now for some tear down...


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## chuyler1 (Apr 10, 2006)

Some test fitting of bucket seats from a Miata, with a bonus surprise hidden inside. Not sure what frequencies I need to run the "thumper" but be assured I will hook them up and squeeze whatever I can out of them. I have new upholstery to install on the seats too, so they won't be brown.


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## chuyler1 (Apr 10, 2006)

Wiring harness kit from American Auto Wire has almost everything I need to throw out the old wiring.










Previously, the entire truck was powered with this lovely fuse box sitting in the engine bay of the truck where it could easily get wet. 










This gives you an idea of the condition of the harness. This was the old emissions box (right) and 50 amp master fuse (left). The thickest wire was about 14 gauge, maybe 12, hard to tell.


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## hot9dog (Mar 23, 2013)

Oh HELL YES!!! you sir have a beautiful example of an amazing truck..... very cool! I'm an old school rotary freak- I'm watching this build.


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## chuyler1 (Apr 10, 2006)

Pulling out the rest of the interior


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## chuyler1 (Apr 10, 2006)

Fabricating a new firewall panel. The old one smelled like 40 years of incomplete combustion and mold.


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## hot9dog (Mar 23, 2013)

That dash is in amazing condition! Damn.... clean example


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## chuyler1 (Apr 10, 2006)

New bulkhead connector. Did I mention I'm doing a wire tuck? All the engine harness wiring will come through this connector in the center right above the motor. All the wiring for the front of the truck is going to be routed through the right quarter panel.


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## chuyler1 (Apr 10, 2006)

hot9dog said:


> That dash is in amazing condition! Damn.... clean example


Yes, the previous owner had a number of trucks and chose the best of everything when putting this one together. I've had the truck 5 years and have done a little restoration of things here and there. When I got the truck the dash was complete but nothing was connected. I had to go through everything and rewire a bunch of stuff...and now I'm doing it again LOL!


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## chuyler1 (Apr 10, 2006)

And now for something you audio gurus will recognize. Full layer of RaamMat completed last night. I've also got the holes drilled and tapped for the bucket seats but two of them are inaccessible from underneath due to the exhaust shield...so I have some work to do before I can mount the seats.


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## chuyler1 (Apr 10, 2006)

Worked on trimming the carpet tonight. I think I'll cover the new firewall board in carpet too.

I also spent some time pulling the wiring harness for the rear of the truck but I got stuck at the fuel pump. Since I have a new pump and filter going in I will have to have a few friends come over and pop the bed off the truck so we can access everything.











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## chuyler1 (Apr 10, 2006)

Some work on the wiring harness this week. 

Ignition switch and steering column all terminated.










Tail light module for a trailer will serve as relay for brakes and turn signals. Easy to replace if it fails because I added quick release terminals. This particular model has a separate 12v power supply so I won't have high current running through steering column switch.










Additional bank of relays for low/high wipers and low/high headlights. This along with the trailer module should tuck up under the gauge cluster out of sight.










Took me a while to translate the OEM wiper relay box into a dual SPDT format I could understand. 










The OEM harness had full power for headlights going through the steering column so I'm going to intercept those feeds and power the lights from a higher gauge cable. 










I also added some RAAMatt BXT to the transmission hump and rear of the cab. I ordered the wrong carpet so finishing it off didn't happen. 






















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## I'm not new (Feb 14, 2015)

Awesome little truck. Looking forward to this build.
Everything looks great so far.


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## zapcoaudio (Sep 26, 2015)

classic import


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## thehatedguy (May 4, 2007)

Love it, but let's move this thread to the right place.


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## JayinMI (Oct 18, 2008)

thehatedguy said:


> Love it, but let's move this thread to the right place.


The audio is coming later. lol

Chuyler, I can't see the pics of the truck. I just see a "-" in each of those. The rest work fine.

Jay


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## JayinMI (Oct 18, 2008)

Found a video of it on YouTube, and a build thread on Mazdas247. Nice.


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## thehatedguy (May 4, 2007)

It's still a build and not a General Audio topic, which was where this was originally at.


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## JayinMI (Oct 18, 2008)

Ah, I found it in the Builds section, thought you were saying it needed to be moved _from_ this section.

Jay


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## chuyler1 (Apr 10, 2006)

Sorry, I started from Tapatalk and didn't realize there was a separate section. No worries, I'm sure people will find it.


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## carlr (Feb 27, 2011)

Subd.


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## claydo (Oct 1, 2012)

A rotary pickup.....sounds like fun! I'm not up on my Japanese classics, I didn't even know they made these....lol. Had a buddy with a first gen rx7 back in the day, wasn't fast or anything, but that motor made it sooooo much fun to drive, it just felt so different....smooth, effortless, and rev happy.


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## JayinMI (Oct 18, 2008)

Back in 77 or 78 when my dad bought his first Mazda GLC, the 1st gen RX7 was just starting to show up on our shores and was extremely hard to get. They were selling way above sticker. A customer at the dealer ordered 3 of them, so he got something of a "bulk discount," and sold 2 of them to other people. He made enough money to pay for his outright, lol.

Jay


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## chuyler1 (Apr 10, 2006)

I've moved on to collecting all the wires for the gauge cluster. I don't have a replacement cluster harness so I may bypass all the circuit board wiring and connect directly to the lights and gauges. Before I do that, I need to understand how it all works. However, while bench testing each of the pins I came across something odd. There is something on the circuit board inline with the oil level sensor. It is preventing the light from turning on. I don't know if it is a failed diode or capacitor. 











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## chuyler1 (Apr 10, 2006)

More carpet came in today so I took a break from wiring to trim and install the rear cab carpeting. Lots of cutting and gluing. I hope the Super77 holds it in place. 











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## chuyler1 (Apr 10, 2006)

Found a box that is a perfect fit for the fuse panel. 











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## chuyler1 (Apr 10, 2006)

Mini audio equipment for a mini truck. 8 channel digital signal processor and 8 channels of class-D 50 watt power. 











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## jamesjones (Mar 8, 2007)

Cool. What are you looking at running with them?


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## chuyler1 (Apr 10, 2006)

Miata seats have head rest speakers and thumpers, so that's 3 or 4 channels depending on how I wire things. Planning for components up front, something shallow, and probably a 6 or 8" sub in the center console. Going to take a while for me to get that far.


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## chuyler1 (Apr 10, 2006)

Spent some time on the seats this rainy afternoon. First shot is the old leather, second is the new Katzkin Leather kit.


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## I'm not new (Feb 14, 2015)

Stumbled on this article just now: 1975 Mazda Rotary Engine Pickup 

Thought you might enjoy it.


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## chuyler1 (Apr 10, 2006)

Yeah I came across that a while back. Despite all the publicity, I didn't get many calls, so I decided to use it as my next project instead. And for the record I have never gotten as bad as 10 mpg so I have no idea what the EPA was doing to get that rating. With a 2,200 lb camper in tow I still got 12 mpg but with no load I could get as high as 17. All bets are off with the new build but I'm thinking mileage may improve a bit with the EFI but when i port the motor it will probably drop.


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## I'm not new (Feb 14, 2015)

LOL, I glanced over it for details and didn't put 2 and 2 together( that it was your truck ).
Haha


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## KrautNotRice (Nov 2, 2015)

This is really awesome!
Sub'd for more oldschool goodness.
Btw I got that Next 5 channel amp from you, it's going into my '84 BMW, I'm mid-build right now.


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## chuyler1 (Apr 10, 2006)

Sweet! I still have the 10" sub that goes with it if you're interested


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## KrautNotRice (Nov 2, 2015)

chuyler1 said:


> Sweet! I still have the 10" sub that goes with it if you're interested


Thanks, I decided I'm doing an IB / trunk baffle install in my 80's BMW sedan so I went with a single 15" sub.


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## funkalicious (Oct 8, 2007)

Having owned an RX-2, RX-3, RX-4 and RX-7 I can attest to their very rev happy nature. Please include the engine build!


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## chuyler1 (Apr 10, 2006)

Been a slow process with other projects going on.

I've got the side mount alternator kit in, and pulleys installed for a wider belt that won't slip as much at high revs. Also note the new electric fan.










The fuse box is in and everything connected except the wires that need to go to the back of the truck. I have to remove the bed to run those.










The rest of the chassis harness is done, including new relays for wipers and headlights.



















All the gauges are hardwired, bypassing the circuit board that had some faulty connections. 










A long way to go in the engine bay. I need a fabricator to mock up the intake manifold since the company I was trying to order from in Australia never came through for me. They gave me the run around for 9 months and I gave up on them.


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## JayinMI (Oct 18, 2008)

Please put a fan shroud on that. It amazes me the number of people who think they don't need one. We just had a supercharged LS-swapped C2500 in the other day and it would overheat like crazy, then the alternator didn't want to work right.

I dig where this is going, can't wait to see it done.

Jay


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## chuyler1 (Apr 10, 2006)

Yeah, I know. This isn't going to be a crazy build, but I'm going to upgrade the radiator before the build is complete and I'll have a shroud made at that point. The OEM shroud isn't going to work.


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## chuyler1 (Apr 10, 2006)

Knocked off some more wiring this evening. 

1) main fuse with shunt for ammeter is in.
2) stereo amp is all hooked up except for speaker wires
3) gauge cluster is in
4) wiring harness for radio is done

Verified the following which was very exciting: Dash lights work with dimmer switch, I can hear low beam and high beam relays clicking on. Radio turns on and remembers presets. Ammeter works. 

Heater 3-way switch does not work. The wiring is pretty beat up. I'm going to have to open it up and clean the contacts. Not looking forward to that because it means disconnecting all the cables and remembering how it all goes back together.


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## oabeieo (Feb 22, 2015)

Nice old cool truck . 
Love it . Bet it's a joy finding parts for


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## chuyler1 (Apr 10, 2006)

Hah, yeah. Had the truck 4 years, only recently acquired the winch to mount a spare tire under the bed. Still trying to find the lug wrench I'd need to use it though.


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## LumbermanSVO (Nov 11, 2009)

I see I'm not the only one who thinks it's a reasonable idea to rewire the whole car, good on you!


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## chuyler1 (Apr 10, 2006)

It seemed like a reasonable idea at the time! I'm just glad the truck has a simple wiring system. If it had more modern components this would be a complete nightmare. Also, this is one of those things where the budget goes completely out the window. I'm constantly ordering more connectors.


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## LumbermanSVO (Nov 11, 2009)

I used an American Autowire Highway 22 system in mine and the price is pretty good for what you get, and the instructions are great. it's when you start adding on and upgrading that the price starts jumping up dramatically. I easily have $1500 in mine so far and I still have stuff to finish.


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## chuyler1 (Apr 10, 2006)

Yeah, the AAW kit was a good start, and I doubt I'd be any better off with a kit from another manufacturer. The wire quality is good and the labeling is fantastic for someone like me who has trouble seeing colors in the dark confines of under the dash. However the kit was missing some basics you'd expect for even a hot rod install (like reverse light wiring).


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## chuyler1 (Apr 10, 2006)

Heater fan switch and controls restored with new harness and cleaned up contacts and stretched springs inside to make sure it will work like new.


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## chuyler1 (Apr 10, 2006)

Center console is in, checking off more circuits...



















1) Radio is wired up and sending audio to the amplifier

2) Heater controls are wired up and functioning 

3) All dash lights work with the dimmer

4) 12v acc works

5) Parking brake light works

6) harness for trailer brake controller is ready to go

7) Exhaust Overheat light is wired, but haven't tested the sensor, not even sure i will install it. I might use the light to display something from ECU instead.


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## chuyler1 (Apr 10, 2006)

Wire tuck for the front end complete. I can check off turn signals, marker lights, head lights, high beams, horn, and electric fan. It's nice to see this old face again. 




























I'm also working on a panel to mount the ECU and O2 sensor module.


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## chuyler1 (Apr 10, 2006)

After months of waiting, I finally have an intake manifold. 





































Last night I started messing with the throttle linkage. Some assembly required.


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## KrautNotRice (Nov 2, 2015)

Very nice!


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## chuyler1 (Apr 10, 2006)

Making progress this week.

Rear lights and trailer hitch are all wires up now. Turn signals, hazards, brake lights, and reverse lights are all up and running. 

O2 sensor, reverse switch on transmission and starter are all plugged in. 










Coils are mounted and custom short spark plug wires connected.










I fabbed up a bracket to mount the vacuum line manifold to the back side of the throttle bodies using some angle aluminum from Home Depot.










Lui stopped by to help out with the engine wiring harness. 



















Meanwhile I snaked 8ga wire through the cabin to connect the alternator to the fuse box. 










We need to figure out what size injectors fit this fuel rail and procure a few more fittings, then we should see this truck up and running in a week or two.


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## sykostek (Apr 23, 2017)

Reading this for the first time. Lovely truck. Great work. Excited to hear that it runs.


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## chuyler1 (Apr 10, 2006)

Swapped out the old fuel pump fora walbro unit. I will revisit this later with proper fittings but that will require removing the bed to access the rest of the lines.


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## jode1967 (Nov 7, 2012)

will be a beautiful ride when you are done. loving the little things.
I am guessing some port work on the engine?
the daughter has a nice 83GSL


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## chuyler1 (Apr 10, 2006)

Street port will come later once we get it up and running.


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## chuyler1 (Apr 10, 2006)

Coolant ports blocked off, OMP blocked off (going to pre-mix), intake finally bolted in place, and vacuum lines sorted.


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## chuyler1 (Apr 10, 2006)

Working on the fuel system.


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