1982 IMSA Endurance Racer Build- The Shrike
 

Hello all!

I'm starting this thread to chronicle the build of my race car. For those of you who didn't see my new guy post (which I'll link at the end of this paragraph) I bought a Pro-7 racer in June 2020 and I've steadily been getting it back in race ready condition. The short-term goal is to get the thing on track and get seat time so I can become a better racing driver, the long-term is to build the car into a period-correct, SVRA Group 10 IMSA racer specced out for endurance racing (think 24 HRS of Daytona) that would make Racing Beat, Kent Racing and Allan Moffat proud! Sadly that's a ways away.
new guy post: https://www.rx7club.com/introduce-yo...-mozu-1149727/

Currently the engine has oil pressure problems, and I believe I've narrowed the cause down to a bad front cover o-ring. The gauge behavior pointed me to look at that, as the oil pressure is fine while the engine is idling while cold, but drops off massively as the engine revs and as it warms up. Here's the thread where I tru to figure that out: https://www.rx7club.com/general-rota...osing-1149741/

I've ordered all the parts I believe I'll need from Mazdatrix. It cost an absolute fortune, but they had the parts all in one place so I decided to in this case the cost was worth the convenience. I plan on having the engine out of the car this weekend and we'll see how quickly I can get it back in the car! I'm going to be swapping out the stock 12a oil pump for the 17mm 13b pump, putting in the Racing Beat street oil pressure regulator and oil baffle and getting the front cover o-ring fixed and the cover sealed back up on the engine.

I'm absolutely terrified of messing up the thrust bearing stack though... can anyone give me advice on handling that part? How do I rebuild the stack?

P.S. Every good project needs a name, so I've chosen to call my racer Mozu, the Japanese word for shrike. Shrikes are mean little birds who have a penchant for impaling their prey on sticks and the like before eating it. Something about a stabtistic little bird impaling large prey made me think of the small but mighty RX7 racer I want to build! It may be childish but at least its FUN!! XD

Since you're removing the engine, keep the front of the engine facing upwards when it's on the stand. I think that's also the easiest position to remove/install the oil pump.

Here's an assembly video, at about the 45:00 mark shows how the thrust bearings are installed.

I was going to say buy a rebuild video but forgot about youTube :). It isn't hard if you have a dial indicator and a magnetic base,

Since you are not tearing the engine completely apart the thrust stack on the front of your engine is probably fine but check it before you take take off the oil pump sprocket. If it checks out, just keep track of the parts and the order they were installed so you can reassemble it the same way.

Looking forward to your build. I have researched that SVRA class but I think my car has too much done to it to be legal.

no need to be scared, just measure it before you call it done
https://cimg5.ibsrv.net/gimg/www.rx7...cea6e59819.png

Pro7 cars are a great starting point for a hot rod!

Thanks fo the video link! Keeping it vertical is the most important thing I've read on every thread I could find on the subject. I've also read that standing the engine on its flywheel to load the E-shaft, in a similar way to depressing the clutch, is a good idea. I'm heading up to Mazdatrix to pick up my parts today and I hope to get working soon!

I'm sorry I missed you posts, y'all they didn't load on my carppy work wifi while on break! :/
I bought the Mazdatrix video and I'm definitely gonna watch a ton of YouTube videos to help me figure it all out! SVRA is the organization I'd really like to race with for the period nature of the cars. It seems fun to race these things against what they would have raced against back then, but a super modified FB does seem like great fun too! I love you yellow racer! that thing looks awesome!

That diagram is GREAT! Thanks so much for posting it here; it'll be a huge help! Pro-7 cars seemed like a great starting point for me. They're so close to stock it'll really allow me to get great seat time and hone my skills as a driver, but they're also such a great canvas to build a gnarly racer in as my skills (and wallet!) get better and more accustomed to racing. :D

Well today didn't go exactly as planned! I managed to get the engine out of the car, but I didn't get to accomplish much more than that. All I was really able to do was install my Racing Beat street oil pressure regulator and shim the front ORP to match. I could NOT by any means remove the E-shaft pulley! The FSM says its only on there with up to 87lbft but I simply could not get it to budge. I tried using my generic flywheel stopper tool, the kind that resembles a crowbar with a hook, and it simply wasn't enough. I guess I'm stymied until I can get that stopper tool and get the pulley off! Does anyone have any advice on that? Am I missing something??

I won't deny, I'm bummed I didn't get more done than I did. It was quite disheartening to get hung up so badly, but hell that's just how any car project can be!!
https://cimg5.ibsrv.net/gimg/www.rx7...5d1d4c47ad.jpg
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I would recommend one of the flywheel stoppers made for the rotary engine. Mazdatrix sells them and they are reasonably inexpensive.

As for the eccentric shaft bolt. Ingersoll Rand makes torque multiplier sockets called Power Pockets. You'll want to hit up Amazon or eBay and search:

Ingersoll Rand S64M19L-PS1 19mm Power Socket

They work wonders for removing the eccentric shaft bolt. It does look like you're making excellent progress! Ad you took the engine out and set it on the flywheel. Much less risk of something going wrong during install.

You might need to use MAP gas on the front bolt if they used lock-tight.

With the engine on the ground I usually bolt a long steel angle to the flywheel as a stopper.
I've been able undo the front bolt and rear nut with a 3/4" drive socket and a 3 foot pipe over the breaker bar. Leverage more often has worked for me over an electric or air impact wrench.

That seems like the path I'll have to take. Those sockets are damn expensive! But they just may give me the edge I need to get the nut loose. I hoped I could get away with not needing to buy the stopper but my generic on isn't cutting it. :(

Is there any kind of Locktite on the front pulley? Is that something that's done by some builders when they reassemble the engines? That thing is ON THERE!

I definitely tried the leverage route! My old man is 6'5" and beefy all around, good viking stock, and I had him try to break it loose while I held the flywheel with a 5 foot piece of DOM tube left over from a roll cage build. It didn't budge!

I've been chatting with Daniel from Garagelife here in SoCal for tips and tricks and expert advice on how to get this done. I may just bite the bullet and have him tackle the little bit of work that is left just to have it done, considering the socket and stopper is gonna come out to at least another $100. He can also double check the work I've already put in to ensure that I've done it properly. Either way I work Sun-Fri so I'll have to wait until next weekend to get working on it anyway!

You may want to reach out to Carl here on this site. He is in the SD area, a long time SCCA and endurance racer, probably has raced against that car many times, and is a nice guy. He once delivered free wheels to me at Laguna Seca! I bet he or his crew of fellow Rx7 racers have resources that could help you out.

If you really start towards an IMSA GTU replica you should reach out to Mitch Schwartzburg who is in SoCal and has been building one of those for a while now. Brandon Droese from Santa Barbara is a young fast E Production racer who happens to have taken over the Mariah fiberglass business and can hook you up with the fiberglass. Rotary Engineering SB.

The front e-shaft bolt does not hold the pulley on. With that said, many rebuilders do use locktite on the front bolt. A flywheel lock and an impact wrench with the air tuned up to 100lbs has worked for me.

Alright you guys the work has been tackled! After talking a bunch with Daniel from Garagelife I brought the motor up to him because I needed some help. I showed up shortly after opening on a midweek day so I could watch and learn how to remove and replace the o-ring properly. Long story short we busted the front cover off and my suspicions were confirmed: the o-ring had totally blown! While we had the engine apart we also replaced the stock 12A oil pump with the 13B pump and replaced oil pickup tube. Luckily I hadn't oil starved the engine or trashed the bearings running the engine with such low pressure while trying to diagnose it. The tear down, inspection and rebuild took a couple hours. The work coupled with the 5 hours or so of driving had me back home with little daylight left, But I managed to get the engine back in the car anyway. Reinstalling the engine proved to be an absolute BITCH! First-off, the engine hoist I was borrowing was far too short to work the engine from the front of the car; I had to go over the passenger side fender. Secondly, I didn't take the intake manifold off of the engine (I wanted to disassemble as little as possible) so the whole engine constantly wanted to rotate down toward the passenger side! I managed to get the transmission input shaft into the (new Racing Beat 4-puck sprung) clutch disc and pilot bushing, but because the engine was uncooperative in all 3 dimensions I couldn't get the surfaces to mate. I ended up muscling it into alignment and sliding the trans bolts into the engine and slowly began to walk it back to the trans. It was a hassle but it worked! I buttoned it all up, filled it up with all necessary fluids and fired it up... SUCCESS! The Racing Beat regulator worked great and the O-ring caused pressure issues are gone! Then engine keeps a steady 80 PSI from idle all the way to my 7200 RPM shift light! It was a minor ordeal and took 2 weeks longer than I wanted but that job is finally complete!

Next we'll be on to wiring the car and messing with some interior parts!
https://cimg6.ibsrv.net/gimg/www.rx7...62939515d9.jpg
Loaded up and ready to go!
https://cimg8.ibsrv.net/gimg/www.rx7...a200e3dce0.jpg
There's the culprit...
https://cimg0.ibsrv.net/gimg/www.rx7...7aa633432d.jpg

I should definitely reach out to them all! Pardon my technological ineptitude but is there a way to search their names on the forums so I can reach out? I found Rotary Engineering with the help of Google and YIKES that's a pricey kit. Its totally worth it if I choose to go that route, I'll just have to save my spare change and earn it! I have dream of a p-ported engine and a widebody racer, but my skills aren't up to that yet anyway! If I don't go with the Kent Racing style GTU kit that Brandon sells I'll go with the Moffat Daytona 24 car. I really its blend of Group C and GTO bodywork. Either way that pretty far down the line... sadly. That all also has me wanting BBS mesh style wheels but finding them in 4x100 seems an impossible or expensive task! I may contact Diamond Racing Wheels about some 15x8s or 15x10s when the time comes.

Thats exactly the course of action we ended up taking. Once I was able to put that stop on it came right off!

I went to main "Search" on the forum, chose "Advanced" and put "Carl", it returned this gentleman...

https://www.rx7club.com/members/carl-22089/

Wonderful thanks! & thank you greatly for not flaming me like the FNG I am!

This video has been a long-time coming; here's the car running with the engine repaired! I apologize for being an awful videographer but hell, I tried! Can anyone who knows anything about racing rotaries comment on the idle? Is that just how high-rpm, performance oriented motors sound at idle? After talking to the builder we aren't sure its bridge ported after all. Currently it idles at 2000 rpm. Now that this is complete, its time for me to begin the next part of the build... REDOING THE ENTIRE WIRING!! I've never wired anything before so it's time to learn I guess...

Sounds like a bridge port to me. I had a street port that would lope like that if I played with the carb a little but mostly they just sort of drone louder than a stock port at idle. Interesting, I thought Pro 7 cars were stock port 12As? The ones I ran against in Colorado all had "stock" ports and were not as fast as me in a straight line.

Based on the sound I was under the impression it was a bridge port as well, but I don't know for sure as I didn't ever stick my finger down the intake runners when I had the manifold off to check if it had been ported. Daniel at Garagelife said that you can get a lopey idle if you mess with the timing and/or the carb. I messed with the timing a little and heard no appreciable change, and the intake was on another Pro-7 12a that had stock ports and had no lope at idle at all. It would be weird if it was ported as I was told it was pro-7 motor and class rules don't allow porting, but perhaps I was misinformed. Either way it runs so I'm not complaining!!

Nate,

Did you buy the car from 7's only in Buttonwillow? I know they had it for quite a while prepping/maintaining it for Richard. Tom Dragoun should be able to tell you if the engine was bridge-ported or not. I know he had a couple of BP's sitting around in his shop for a long time. The other possible more likely scenario now that I think of it is that it has the "Dragoun" tuning of the carb. Tom, for some reason, tuned the carbs super-rich (lots of times black smoke coming out the exhaust while idling through the paddock) on the primary side. He liked 140's in the primary side and 130's in secondary. They basically run like crap until the accelerator pedal is matted. That also means if you are going through a corner at part throttle it will hesitate. Really annoying in my opinion, but seemed like a lot of people liked/lived with it. I ended up running 100-110 primary and 160-170 secondary with the stock port. Same HP, but smooth idle and throttle transition. Maybe didn't feel as powerful to people, because you didn't get the kick in the pants after it stumbled before finally taking off.

Carl

Hi Carl!
Yes Tom and 7's Only did maintain the car for Rick for the 7 or so seasons he raced it as far as I'm aware. I know that when the engine that came with the car was rebuilt at Mazdatrix they tuned the carb an dyno'd the engine. That dyno sheet shows the engine topping out HP wise at 120 HP at 7200 RPM. I'm not sure if after that Tom tuned or modified the carb in any way. The interesting thing is that engine, with that carb, idled with a smooth drone at 2000 RPM. That engine had worn seals when I purchased it so it did start and run if the car was pulled or pushed to a high enough speed, and I ran it a few times to feel how the car handled and drove. I got on the car with that engine pretty hard a few times on private property and got a decent feel for it in that guise. In comparison the engine currently in the car was also purchased from Tom, who had it just sitting in the shop by the door; somebody else had backed out of a previous sale so I was able to get it. He told me it'd come out of a Pro-7 car that had been rolled so I assumed it was stock port like the worn engine. The same carb put on the mystery motor idles as the video shows: with a lot of lope and some brap, also at 2000 RPM. The butt-dyno also seems to register a little more pick up when I get on the gas pedal. Perhaps Tom was wrong about the engine's origin? I guess I won't know for sure until I need to have the intake manifold off next.

It is probably worth determining whether or not it is a bridge-port. Tom tried to sell me a 12a a couple of years ago that was sitting by the shop door too! He said it was bridgeported from/for one of the 3rd gen GT2 cars he was running for a while. If it is a bridgeport and you are using a stock (but stripped) Nikki, you are giving up a lot of HP. I recently rebuilt my 12A with a mild street port. With a stock Nikki I got 135HP and with a primary-venturi-bored Nikki have 150HP. Same day, same dyno. I assume the difference would be more dramatic with a bridgeport.

If you haven't pulled it apart already, it is very easy to pull off the carb air horn so that you can check the jetting (have to also pull off the side access plugs). At least you could put that question to bed quickly.

If you don't want to pull the intake (which as I am sure you have noticed is really simple) you could get a wi-fi boroscope for $30 that you can view with your phone or computer. You should be able to stick it down through the intake after removing the carb.

As an engineer-in-training and mechanic that is all no doubt obvious. Old guys like me always just say it anyway, frequently to the chagrin of their kids ;-)

Good luck

Carl

It is definitely something I should determine at some point. If it is indeed ported in any way the carb is robbing it of power without a doubt! I was hoping to get a weber IDA set up for the this particular engine anyways so sooner rather than later that issue may be rectified. My goal for having the 2 engines is to have one set up in a (comparatively) mild state of tune, basically as a Pro-7 motor, and to have the other as hot as I can run without hurting the reliability too much. I would love to build a peripheral ported 12A at some point, but if one of the engines already happens to be bridge ported I'd settle for that!

I should look further into that endoscope check; it seems like a quick way to determine for sure. In all honesty, the questions about it sidle were asked to see if anyone noticed anything glaringly wrong I may not be aware of with my lack of rotary knowledge. Since it all seems that it may be ok I may not do anything else to the motor in the short term. I'm actively saving to have the other engine rebuilt in a few months' time and as soon as it is, it's going back in the car. I don't need more than a stock port motor to learn how to drive well! At that point I can really tear into and properly build myself a ported racing engine. I love the idea of having different engines set up for different classes because they're so easy to pull and swap in a stripped out racing set-up. At this point I can have my engine out in less than an hour!

Most younglings may balk or roll their eyes at hearing that again, but I'm always appreciative of the advice! Forgetting things is all too easy it seems.

On a question relating to electronics and wiring, has anyone tried any of the aftermarket wiring kits that are out there? I've heard good things about Painless brand kits and components, but their stuff is pricey. Anyone have an other set-ups they like using? My car has been completely gutted of all factory electronics and its running literally nothing more in regards to electronics than is required to run the car. It doesn't appear to even have a fuse box in its current guise! Considering I'm wanting to run endurance's races that include nighttime running I figured I'd just begin learning to rewire it all now; it seems as good a time as any to start.

i did a car with the painless kit once, and it was anything but. every car in the world is switched on the negative side, so power goes into whatever thing, and then the switch is on the ground side. the painless has the switches on the positive side, so its totally incompatible with any stock parts more complex than a lightbulb. the car i did is an endurance racing miata, and i had to switch the painless kit to switching on the ground side and then integrate the stock Mazda ECU, it works, but it was a TON of work, and i'm not sure that there was any real benefit.

Tanks for highlighting the switching issue! Luckily in this case, the OEM wiring is all but gone from my car, so I'd be starting try wiring from scratch anyway. If I choose to use Painless parts I'll be sure to buy everything I need from them so as not to mock anything up

Alright y'all, after quite a bit of internet research I think I've decided on these parts from Painless Performance to rewire my entire car:
https://www.painlessperformance.com/wc/10102
https://www.painlessperformance.com/wc/30129
https://www.painlessperformance.com/wc/30131
Anyone have any opinion of my choices? Keep in mind the car doesn't have any of the original wiring left, and is just wired to be able to run a sprint race. so I'm going to redo the whole thing from scratch. Also, my desire for so many extra circuits is my plan to enter the car in endurance races and I'd like the extra circuits to run the coolshirt system and the radio and all the other stuff that may prove useful. Lastly, due to differing states' definitions or road-legality the flasher relays in that wiring harness may, completely theoretically, one day serve a purpose! ;)

Those are nice kits and seem very sorted and well made. If I was building a street car or hot-rod would definitely go with something like that. For a racer on a budget, including endurance racing, not sure it is money well spent. When I wired my car from scratch, the biggest cost items were the switches(Console/Kill) and 0 gauge wire I used for locating the battery shotgun. These ticket items are not included. These kits includes options for a lot but must of it is unnecessary for a carbureted racecar.

I have three RX7 racecars, and none of them have rad fans and didn't bother with a relay for the fuel pump. You do need proper rated wire, switch and fuse for those. You can probably buy what you actually need for under $100 vs. the $400 after tax and freight. I would save the $300 for something else. Seems like most of what you actually need is on the car now and you just need a few more circuits. You will need the same tools, knowledge and expertise to install regardless of where you source your materials.

My $0.02. Projects are fun but you have a running racecar. Buy what you need to get it on the track asap. That's the whole point of owning these things. Don't worry about postponing some of your build plans, cuz racecars are never done. BTW, endurance racing requires a team, lots of spares, and can put a whole season of wear&tear on the car in one weekend. I would recommend talking to Carl about how to do it right.

I'm definitely appreciative of you $.02! Why don't you have fans on any of your racers? The reason I want an electric radiator fan is that Daniel at Garagelife suggested to me that one of the best ways to improve the longevity of a racing rotary engine is to allow it the chance to cool down some after a race, especially an endurance race, to prevent the internals from becoming heat soaked; he advises treating it similar to a turbo engine and letting the engine run at idle with the fan on and fluids circulating after using it hard. Does your (or anyone else's) opinion on that differ? I'm always open to input from y'all who have experience running these things.

Perhaps I'm just a little paranoid, but I was wanting nice relays to make the electrical systems a little safer. I've seen couple fires in project cars from dodgy wiring and I'd like to avoid that at all costs! I understand that the wiring harness I linked above may be overkill, but I like that, in theory, it's made to be quite simple to adapt to one's custom application. Perhaps a smaller, less expensive version of the same idea would be better. That $300 could be used on a weber manifold for my 12A!

Carl and I have sent many messages back and forth talking about endurance racing already! I'll undoubtedly be pestering him again with questions but he's given me a ton of advice already. In regards to prepping the car for endurance racing: I already have a team of drivers in mind! My dad, my best friend Logan, (both avid track day participants) Logans's dad (the owner of Kundensport in Oxnard, CA and an avid 911 racer) will round out my team, leaving me the weakest driving link! The fact that you can count 2 amateur, 1 apprentice and 1 professional mechanic among the 4 of us has me thinking we'll be pretty solid once we can find a rhythm and be a half-decent endurance racing outfit. That being said I don't have any drivetrain spares currently, though once I have enough money saved to get my original engine rebuilt I'll have a spare motor. I'd like to source a spare transmission before I start trying to seriously enter any endurance races. Much further down the line I'd like to change both the transmission and rear end to something with greater support and availability, perhaps a Tremec and a Ford 9" or 8.8" but that's quite an expensive proposition so for now its nothing more than a pipe-dream!

The car runs and drives now so I'm going to hopefully get it to a test-and-tune day and start enjoying it sometime soon! But lights for endurance running is the next goal for the car itself.

This I where I should wait patiently for someone like mustanghammer to jump in. I don’t claim to be as knowledgeable as many of the others guys that advise on these posts, but what the heck. Lot of comments there so will break it down:

one of the best ways to improve the longevity of a racing rotary engine is to allow it the chance to cool down some after a race, Best way to maintain longevity is to not let it overheat in the first place
especially an endurance race, If your cooling system is working you should see similar temps in a 30 min race as a 3 hr race
to prevent the internals from becoming heat soaked;the motor is the heat generator, other than the header and brake discs, it is already that hottest thing in there. Other lower temp nearby objects will be absorbing that heat he advises treating it similar to a turbo engine and letting the engine run at idle with the fan on and fluids circulating after using it hard.An electric fan will never be as efficient as the air exchange that comes from driving, that is what cool down laps are for
Does your (or anyone else's) opinion on that differ? Oh for sure. And He’s not wrong, I just have not found a rad fan necesssary, at least not on a non boosted motor. I do not let me engine idle away in pre or post grid and I don not take long slow drives around the paddock.

Perhaps I'm just a little paranoid, but I was wanting nice relays to make the electrical systems a little safer. They definitely can serve that purpose. Relays are just switches. As a car is a 12v system only, they are mainly used to remove the higher amp circuits from the general public’s finger tips. This is a good idea. As race cars are operated differently than a mini van, you need to judge what makes the most sense. Relays, although fundamentally very reliable, add another component in a circuit that can fail. I’m a big proponent of the KISS principle.
I've seen couple fires in project cars from dodgy wiring and I'd like to avoid that at all costs! Relays wont save you from dodgy wiring
I understand that the wiring harness I linked above may be overkill, but I like that, in theory, it's made to be quite simple to adapt to one's custom application. it will definitely work and it really is a nice kit. But our electrical systems are sooo simple and minimal.
Perhaps a smaller, less expensive version of the same idea would be better. That $300 could be used on a weber manifold for my 12a. You’re getting warmer. But how about instead of a Weber intake, use it for a new harness belts. Don’t need a Weber to get on the track, but you will need current belts.

Carl and I have sent many messages back and forth talking about endurance racing already! I'll undoubtedly be pestering him again with questions but he's given me a ton of advice already. In regards to prepping the car for endurance racing: I already have a team of drivers in mind! My dad, my best friend Logan, (both avid track day participants) Logans's dad (the owner of Kundensport in Oxnard, CA and an avid 911 racer) will round out my team, leaving me the weakest driving link! The fact that you can count 2 amateur, 1 apprentice and 1 professional mechanic among the 4 of us has me thinking we'll be pretty solid once we can find a rhythm and be a half-decent endurance racing outfit. That is awesome. I wish I had that much help!
That being said I don't have any drivetrain spares currently, though once I have enough money saved to get my original engine rebuilt I'll have a spare motor. I'd like to source a spare transmission before I start trying to seriously enter any endurance races. You will need a lot of spares. I generated most of my stockpile from buying rollers for cheap or free, then pilfer and chop to pieces. Better yet, paddock next to Carl’s team!
Much further down the line I'd like to change both the transmission and rear end to something with greater support and availability, perhaps a Tremec and a Ford 9" or 8.8" but that's quite an expensive proposition so for now its nothing more than a pipe-dream! There’s the creep again. If your focus is running lucky dog, Lemons, or ChumpCar, your will probably want to change platforms before doing those mods. If you’re planning on building an IMSA GTU replica(like in the title of the post) I would say keep it Mazda. I do like your youthful exuberance tho.

The car runs and drives now so I'm going to hopefully get it to a test-and-tune day and start enjoying it sometime soon! But lights for endurance running is the next goal for the car itself. other than low amp LEDs, you will need relays for those.

you let it cool on the in-lap, airflow > fan. most of the cars i've built have had a fan, but it doesn't get used much, occasionally you're running it in the paddock or something

relay vs not, use a relay when you need it, to take load off of other things (the stock fuel pump runs through the ignition switch), but don't over do it. not only adds weight, but complexity.

i've done some 25 hour races and some 1-3 hour races, the 3 hours you just need someone to put gas in it, and someone else to hold the fire extinguisher (its in the rules), anything more than gas and you're in the pits too long, so no spares needed.
for the 25 you need to restore the car from the ground up, and then bring enough to do it again, if all goes well you don't need much except tires

i know how to do it wrong! (list is all true, endurance racing is hard, but its awesome)

0. make sure you have a couple of master mechanics on the team, and make sure you don't let them touch the car! use the engineer instead, best if he works on something unrelated, like submarines
1. for drivers consistency is best, we had one (Mario) who got hit by a Corvette, in turn 9, in the right rear of the car, at 2am two years running. that isn't consistency, that is amazing
2. Start building the car a couple weeks before the race
3. make sure the fuel system is full of leaves
4. hose clamps are optional, geysers of water every 2 hours are neat
5. spend more on food than the car, best thing ever is when someone hands you food at like 3am, even better when there is a warm tent and a chef. we have seriously considered getting rid of the car (they are expensive, and dirty), and just BBQing
6. use a Honda! sure its reliable on the street....

this is our first 25 hour car, believe it or not the duct tape is holding it together and it ran its fastest lap like that....
https://cimg7.ibsrv.net/gimg/www.rx7...4724e84185.jpg

An electric fan is the way to go because they don't rob HP like a mechanical fan does (there is an Engine Masters video that covers this - very eye opening) and also because they can be ran when the car is stationary with the engine off. I turn mine on once the car gets started and don't turn it off until I come back in the paddock and park. That said they won't really help with heat soak unless water is being circulated in the engine so not really buying that running it after the engine is shut down has allot of value. However, I am pretty sure I have run the fan for a few minutes after a race so there is that.

To Kurt's point, the best way to keep a Rotary cool is to never let it get too hot. To do this you need a big radiator - mine is 26x19 (but you can fit a 28x19 easily) and I like the dual pass design because it forces the water to slow down and move across the core twice.

Water cooling is only part of the equation because a Rotary engine relies on oil cooling to a great extent. Keep in mind that the rotors are full of oil when the engine is running. So It is the oil that absorbs allot of the combustion heat and not the water like in a conventional piston engine. This is also why a rotary engine will tend to get hotter that faster you run it because more engine speed means more combustion events over a given period of time. This can be exacerbated when a car is fitted with a close ratio transmission because it will keep an engine consistently at a high RPM so it stays in its power band. As a result of all of this, oil cooling is critical. It is why I have run 2 OE coolers plumped in parallel on my race car for a long time. The OE coolers are generally superior to anything in the aftermarket (until you spend big bucks) and having two doubles the effective surface area.

As to wiring, I built my own harness. It was a PITA and was the single most time consuming part of my build or at least it seemed like it was. A buddy of mine used a Painless wire kit for his RX7 race car and it seemed to work very well for him. At the time it was too rich for me so I knuckled dragged my own using allot of 14ga wire and trailer connectors. To me the main things that you need are fuses to protect each circuit, connectors that allow you to remove powered components without cutting a wire, wire colors that help you ID the various circuits in a hurry and really good grounds. On my car I welded bolts to the car for all of my grounds because a welded bolt doesn't corrode or get loose ever.

I knew I should have just waited for Mike and Scott to reply. My overall point is to not get too absorbed in the perfect build at first, but focus on spending your $$$ on what it takes to get it on the track. You are going to find lots of things that need attention once you start driving it and you may need to divert your time and money in that direction. Definitely get it out there with some track day/HPDE sessions before any real racing. The good news is that the car came from a very reputable shop so it should be fundamentally solid, but I am sure there are lot's of maintenance items to be addressed.

And Mario is the man! ;)

or maybe ever!

yes do! sorry for all the thread jacking, endurance racing is a lot of fun, but its also a great way to destroy a car quickly :)

Wow you guys are awesome!! That was definitely a crash course from some of the experts and I'm thankful for all the input on everything! To some up my understanding of what seems to be the big points:

1. Some of you like having an electric and and some don't. I was leaning towards a fan at the beginning and I really haven't been swayed against one so I think I'll pick up an extra shift and get myself one. Worst comes to worst I have plenty of buddies who could use it if I ever take it off; a trade for parts or some weekend help could always be arranged!

2. On the topic of wiring, pre-made kits are nice, but I should reevaluate just what I might need for running an endurance race and make the deciton if I need the complexity, cost and weight penalties to recall do what I want to do. In regards to relays they may be worth that penalty for some of the things that could use them, but certain things do need them. I'll definitely be sure to enjoy the car the way it is now doing much shorter duration outings. I don't yet have a license but I'm hoping to get the car to a track day by the end of April to get my first real time behind the wheel!

3. In regards to building and running an endurance car, spares is the name of the game! That being said spares for this generation of RX7 are getting hard to find, and are getting kind of pricey. It was damn near an impossibility for me to find a small bearing disc brake axle for my car after I discovered my right axle had been bent! I have family that runs 67-72 Trans-Am cars with SVRA and participates in events like the Monterey Motorsports Reunion and the Sonoma Historics, and a good chunk of those guys are running Ford 9" rears in their Camaros and just about anything else they can get it in just for ease of use and maintenance. I know its not strictly the most accurate of builds if parts such as that are used, but to get the experience of driving a period-style IMSA RX7 is the goal, and using easier components is fine with me so long as its still in the spirit of the build. That being said I wish I could keep it all Mazda! I know racing beat built a gnarly rear end for their GTU cars back in the early-80s. I'll burn that bridge when I get to it, but right now its pretty far off in the distance.

4. On endurance racing itself: It's fun but boy can it be an ordeal! I've always loved the idea of endurance racing as the cars have to be designed to do it all, go fast and go until the end! It also seems like a great way to get all those in my life who want to be involved in the racing involved in the racing. It's still the ultimate goal, but before I can get there I have to get racing much shorter, simpler, less demanding races first... and earn the money to build the car the way I want it for endurance races! Sadly no one would want to sponsor me so it's all coming out of my pocket! Oh and that Mario is awesome and that "endurance racing is a lot of fun, but its also a great way to destroy a car quickly! " It's not thread jacking to me when its the entire reason for the build!!

Thank you all so much for being so willing to share all your experience with me! I can't wait to really get this thing on track and get racing for real. Years of pining and hard work are finally paying off!

Speaking of getting the car on track, I'm hoping to take the hoopty to a test and tune day at Willow Springs some time in the next month or so. Do any of you salty old racers have any advice on any things I should change around or mess with when trying to test different suspension set ups? I believe Tom set it up when he was maintaining the car previously, and I'm going to carefully document how the car is set up now before I change anything. I'd like to know if any of y'all with experience can enlighten me to any characteristics or habits these cars have at the limit and what to do about it. I have no experience with cars on track so I have no idea what handling characteristics I'll like to begin with!

Yep the days of going to the local auto parts store and ordering reman-brake calipers for an FB (and even an FC) appear to be long gone. If you have to run stock brakes then it would be wise to start hording calipers when ever and where ever you find them. As long as the piston bores are scored they can be rebuilt.

If you can use after market brakes, the latest SCCA Production brake rule changes offer some salvation. In that class you are now allowed to fit larger rotors and after market calipers. Before this change, approved alternates had to be the same size as stock and had to use stock calipers. Charlie Clark at KC Raceware is working on an upgrade for his hub kits that will fit a 11.75" rotor and a common Willwood caliper. These will fit in a 15" wheel

Speaking of getting the car on track, I'm hoping to take the hoopty to a test and tune day at Willow Springs some time in the next month or so. Do any of you salty old racers have any advice on any things I should change around or mess with when trying to test different suspension set ups? I believe Tom set it up when he was maintaining the car previously, and I'm going to carefully document how the car is set up now before I change anything. I'd like to know if any of y'all with experience can enlighten me to any characteristics or habits these cars have at the limit and what to do about it. I have no experience with cars on track so I have no idea what handling characteristics I'll like to begin with!

The next Willow Springs test day is Friday April 30. The Lucky Dog enduro is the next two days. I will be there possibly for a little testing on Friday and then for racing on Sat and Sunday. Willow Springs is a very bumpy track. You want a very compliant suspension for the RX7. Otherwise you will feel like you are bouncing right off the track in T8 and T9 (plus a few others). Assuming the car was Pro7 legal when you got it, the front springs will be 275-350 lb/in and the rears will be 175 lb/in. Those should be good. I am running 350/200 (I cut the rears a bit to increase the rate). 400/225 is nearly unmanageable and certainly no fun for 90 minutes at a time. On smoother tracks I like the 400/225, but also don't bother changing it anymore. For camber you should be looking at about 2.5 deg. Anymore than that, and I (and others) have had issues with loss of braking effectiveness. I like just a small amount of toe-in, but that is probably more of a driver feel thing. I remember 15 or so years ago at Auto Club Speedway, when I had serious difficulties going in a straight line with 1/8-1/4" (can't remember the exact settings) of toe-out. Maybe related to loose steering box, but still.... Tom's suspension set-up is probably fine to start. I would not even bother changing anything (assuming it is somewhat close to above) until you have a bunch of time on track. You won't be able to tell any differences in the set-up until you can drive the car at a good pace around the track.

As far as a radiator, I do think it is useful to have a radiator for endurance racing. You can easily get stopped for red flag out on track or black flag at pit exit. Under those conditions it is better not to stop the car, as it is possible to heat soak the carb and not be able to start. You don't want that to happen while out somewhere on track and your team can't push start you ;-). You definitely do not need a fan under normal racing conditions. As Scott says, oil cooling is very important. I just use a stock 1st gen oil cooler, with the thermostat removed and the bypass plugged. That is giving me max oil temp of 200 deg. An "oversize" KOYO radiator made for the 1st gen works fine for me keeping the water at 190 degF. I do use a thermostat, so I can keep the oil temp up. Without it, winter/early spring days at Buttonwillow can make it difficult to reach 120 degF, which is not good for the engine either. I used to remove it and block the bypass in the hot season, but I got tired of swapping back and forth and trying to remember what was (or wasn't installed). With the aluminum radiator it stays cool under all conditions with the thermostat installed.

Endurance racing is also not so hard on the car as you would think as long as you stick with a reasonably stock engine. My last stockport 12A lasted 9 years with 11 endurance weekends (about 160 hours) and at least twice as many sprint weekends (probably another 60-70 hours). During that time I had the following other failures that typically ended up with me losing part of an endurance race day: clutch failure, loose diff bolts during last hour of 14 hour weekend, broken header 2 hours before the end of a 14 hour weekend (it was at Laguna Seca, so couldn't just keep going with the extra noise), radiator hose leak when a wire from air intake poked a hole, broken panhard bar after getting punted by an overzealous E36. That is really not a lot of work.

For a stock-ish 12A, a fancy tranny and rear end is a waste. In 20 years I have bent one axle shaft and had one transmission fail (I have replaced two other trannies that were still driveable but had scratchy 3-4 shifts, but they were junkyard trannies with unknown history) . For the transmission, miata center section works great. You just need an extra first gen core to use the bell and tail housings.

As far as lighting in your car I think you are getting way ahead of yourself, I just looked at the LDRL and Champcar 2021 schedules and there is only one event that extends into the night and that is in Washington or Oregon. No idea about Lemons tho. In any case, even for a normal year, there are at best 1 or two night races in California.

I agree with everything Kurt, Mike (j9fd3s?) and Scott have to say. All good advice. Get the car up and going and drive it. You can improve things as you go along. The base build by Tom should be good enough for you to have fun at LDRL and Champcar endurance events too. Just be sensible and make sure you have done your best to make sure everything is ready and bolted together right, at least several weeks before you go out. KISS system is the best.

Definitely get a cool shirt system for endurance racing in California. Also pay attention to driver comfort. You will find what works and doesn't as time goes on.

I am looking forward to meeting you at some point. Maybe at Willow Springs at end of April.

Cheers,

Carl

1. up to you, can't really hurt
2. you'll want a relay for the fuel pump and maybe the coils, you want as much voltage as you can get there, and it takes the load off the switch(es), but other than that there really isn't much in the car.
3. in 1979 Mazda showed up with 265hp/2050lbs cars and they were ok, but they got penalized up to 2250lbs (from memory) and then they started having axle troubles and switch to 9" Ford stuff, so its not Mazda, but it is period correct.
4. i'll put up a thread here in a shortly, but a friend of mine built a lemons car out of a GSL-SE, and we had it out this last weekend. the good part was that we got lots of track time, and they don't need a racing license, the bad part with 152 cars on track its more like the 405 than a track day... or driving the truck and trailer through San Francisco at rush hour or something

I was following up on Mike's (?) comments and realized that I had a couple of typos in my previous entry. Yes, you obviously need a radiator :-) An electric radiator FAN can also be helpful in endurance racing when you get stuck in a red or black flag situation. As Kurt commented a fan is not needed for sprint racing. I actually did not use one for several years while endurance racing either. I got pretty antsy a couple of times though with the driver sitting at black flag waiting to get released.

Also when talking about using a thermostat, I meant that the water (not oil) temp would not get over 120 degF when I was driving in cold conditions at Buttonwillow with no thermostat. If you decide not to use a thermostat you have to remember to install a plug in the bypass channel, otherwise you will bypass a bunch of water around the radiator and no doubt overheat because of that. I forget the size of the plug, but you have to tap the bypass for the plug. If you need the size at some point let me know and I can pull the plug out and measure it. I am thinking maybe 1/2"npt?

Anyway, hope to see you in a few weeks at the Willow Springs test day.

Cheers,

Carl

In my experience, the bypass hole will accept a 3/4 NPT tap without being drilled. Also if not using a thermostat, I would recommend using a restrictor with a .75" hole. Moroso sells them in various sizes. I think the Mazda T-stat is fail safe - meaning if it fail it stays open and blocks the bypass but I don't know this for sure. I never wanted to find out.....

Regarding racing in cold weather, our approach is to tape of the grill opening and not install a t-stat.

I run my E-fan all the time when I am on track. If I tried waiting until it was needed but I found that I got distracted and engine temps got high. With a bigger radiator and a vented hood now I will try running the car without it one in qualifying to see how it goes.

Sadly it just seems to be that time in these particular models' lives; they're old enough to be scarce but not old enough to have had a large after market rally behind them and make parts for them like Mustangs etc. I've made no commitments to any class yet, so the option does exist for me to chose a spec that does allow for aftermarket brakes of any sort. For the long-run that may be the best set-up for me and my ability to enjoy years of track use with the car!

in regards to there being ford 9" rears in period IMSA RX7s I remember reading an article about the Racing Beat GTU car n the early 80s that made specific mention of the rear end and rear suspension having been extensively modified. If I remember correctly it made mention of a gnarly 3-link with full floating axles or something like that. It sounded very much to me like the set up my uncle runs in his 1970 Z28 trans-am racing Camaro! That car is a legitimate, authentic period car, but I'm not aware if the 9" is from its original racing days or not. I'll have to ask him

Carl, my concerns about sitting for any reason while at a race are my exact desire for an electric fan. I'd hate t cause any kind of temperature related issues form something so silly and easily avoidable; and Scott I am of the same mindset as in regards to running with the fan on to prevent me from forgetting to use it! Sadly I have those kind of tendencies! In regards to the thermostat comments I have no idea whether or not my car has one in either cooling system come to think of it. I'm not sure if the water t-stat has been removed, or whether or not the oil t-stat is in as well. I'm inclined to nit bother checking until I run into the need to given that the little driving and running I've been able to do of the car hasn't lead to any kind of overheating issues. I actually haven't really touched my car these last couple weeks as I've just ben slammed busy! I'll take some pics of my aftermarket radiator and post them here in the next coming days and y'all can tell me what you think.

In regards to the test & tune on the 30th, I'd really like to go! I'll have to see how my plans work out and how busy I am. My biggest hassle is the need to borrow a truck and trailer to get it out there given that my old man will have the truck that day already! Perhaps I can rope my uncle or one of my coworkers into it! We'll just have to see how sit all pans out.

HA! It took me a little while but I found the article I was after describing Racing Beat's GTU car in much more detail!
https://www.racingbeat.com/gallery/C...20Jan%2081.pdf
I thought it could have been a Ford rear end, but apparently its a Halibrand set-up... NEAT! I wonder what front hubs they ran and what bolt pattern the wheels were. I hate the 4x110 pattern's lack of availability

and to follow up on Carls comments, we run a radiator too, and a thermostat. my friend tried without the thermostat (plugged the bypass), and it really didn't seem to make any difference.

the lemons car was getting hot this weekend, and we made a radiator/oil cooler duct out of cardboard and duct tape, and it did help, so that is something to think about. the lemons car ended up with an oil cooler behind the round bar up front, which is nice because its protected, but i think it needed more airflow.

Cool article. I remember seeing it in a C&D my Mom brought home from the school library. She used to bring all of the aged out car related periodicals home for me to read. Little did she know the monster she was creating....

The main take away is that after all of the development time the end product was fast but there wasn't must "Mazda" left in the Mazda. This is pretty much what happens in any class that allows for competitors to make modifications to a car to make it "competitive." Usually the rules makers try to hold the line but constant pressure by racers driving popular cars causes rule creep.

You can see examples of this in SCCA E Production where RX7s (and other spindle strut cars) have been allowed to fit alternate hubs because the OE rotor/hub assembly were prone to failure. The latest big change is to open up brakes so that you can fit anything you want as long as it fits in the specified wheel and uses no more than a 4 piston caliper. Before all of this, alternate transmissions were allowed (bring on the Jerico's) because those were a problem too. All of this stuff does make racing better and it does allow an old dog to be competitive but it adds cost and complexity to a race car.

So while you are deciding what to do you with your car, keep these things in mind. Of course this is coming from a guy who has a crew of one and just enough disposable income to be dangerous. I really miss my IT7 race car......and racing with other slow cars.....and tires that didn't take a second mortgage.