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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
Last edited by IMSAaspirations; 02-09-21 at 01:37 PM.
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?
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.
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! :/
Originally Posted by mustanghammer
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.
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!
Originally Posted by j9fd3s
no need to be scared, just measure it before you call it done
Pro7 cars are a great starting point for a hot rod!
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.
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!!
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.
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.
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.
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.
Originally Posted by KansasCityREPU
You might need to use MAP gas on the front bolt if they used lock-tight.
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!
Originally Posted by j_tso
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.
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.
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!
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! Loaded up and ready to go! There's the culprit...
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.
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.
Originally Posted by KansasCityREPU
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.
Thats exactly the course of action we ended up taking. Once I was able to put that stop on it came right off!
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.
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!!
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.
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 ;-)
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.
02-09-21, 01:34 PM
. It isn't hard if you have a dial indicator and a magnetic base,
