My VW baja - potential rotary project
 

I just picked this up a couple weeks ago. Knowing me, I can't leave well enough alone. I'm planning on doing a rotary in it. Naturally aspirated of course. It'll be a 4 port 13B with no porting for maximum low RPM torque and reliability. If I need more top end in the future, a port job would be no problem. I've got almost everything I need except for the adaptor plate, flywheel etc (probably from KEP) and the cooling tubes. I just have to do a little more research into minimal porting configurations before I build it.

Paul Yaw said something about opening exhaust ports late and keeping them small for torque which peaks at around 4k RPM. That'd be perfect for a baja since VW trannies were designed for not much above 4500. I have a set of late opening late closing rotor housings from some J-spec engine. The ports are sorta big compared to US-spec from the same era (thermal reactors), but it's ok since US-spec is known to be small and restrictive. I figure the cross sectional area should be right on the money requiring no porting. Coupled with stock intake ports on the side plates, it should have great low end and driveability on a Hitachi. Think 1st gen sized intake ports. :) (they were stock on all 12As and 13Bs from '76-'83) I'll smooth out the casting flash and 90° edges inside, of course. Then finish it off with a textured surface to reduce fuel wetting-out during quick stabs of the throttle.

I may even commit rotary retardation and use a beehive for simplicity. The water cooling would need to be adequate, of course, and it obviously will since I'm building it. ;) A radiator up front is the only way to go. The cooling tubes will increase total fluid capacity a little. A drilled thermostat will help with thermal shock (thanks ZenJoe for the idea). I can't think of anything else. Oh yeah, an FC waterpump if I can find one for a little weight reduction.

I think the above is a good introduction. Here are some pics of the car. Let me know whether you think a carbed 13B will have a good home here.

https://www.rx7club.com/forum/attach...d=203276&stc=1

https://www.rx7club.com/forum/attach...d=203277&stc=1

I found the Paul Yaw article. http://www.yawpower.com/febtech.html

It looks like the only thing I won't take advantage of is a long primary header. No room. I want to keep this baja small and simple. It'll be a far cry from the overbuilt behemoth found on my web page. http://www.geocities.com/cd23c/cars.html#rebaja (it's geocities so if the pics don't show up, wait a couple hours) I may still do the two tone engine paint scheme. How about burgandy and silver? Burgandy side plates and silver rotor housings, front cover etc? If can find that shade in a rattle can, then sure, why not.

I hope your next post is after you take it off some sweet jumps ;)

Great looking Bug you picked up. Takes me back a few days.

Thanks guys. I don't really trust the ACVW enough to want to pound on it, so no jumps for now. ;) The blinkers and other lights were never hooked up so I've got to do some electrical before I drive this thing much. I think I'll hang on to the ACVW because it's a complete running engine. Maybe I'll find a home in my garage for it. I'm running out of space though.

Here's a question for the porting guys. First let me explain the situation. The R5 intermediate plate that came with the doner engine had really small short ports. Think FC on the inside and really short on the outside. Now I know this will work with the original rotor housings, intake manifold, carb and exhaust ports as a unit, but I also have access to a Y casting intermediate plate from a 12A with tall ports on the outside and normal 12A sized stock ports on the inside. Keep in mind that the original front and rear plates' ports were identical in size and shape to a 12A or 13B from that era; only the intermediate plate had tiny ports. The carb had tiny fuel jets (90/140 - that's small!) and huge air bleeds (90/160) and the thermostat was a 190°F unit. This all tells me that this engine was intended for very low RPM and rather warm operation. I believe the spark plugs were also B6ET where 6 = an extremely hot plug which would resist fouling under sedentary driving conditions, like in a luxury car. Oh, and it had an auto rear counterweight putting me that much ahead in installing it in the baja. It probably came out of a Luce or something. :)

Ok, now that you've gotten a bit of brackground on this potential doner engine, and we know the intended driving style in a baja will differ a fair amount from the original intended driving style of a typical luxury car, which intermediate plate should I use? The choices are the tiny ported stocker or a nitrided tall port Y plate from a 1st gen 12A.

Since I can easily change jets and air bleeds in the Hitachi, and have had nice results so far with this carb on a streetported 13B with a tall ported intermediate plate (the low end torque was surprising), I think I could get away with a tall ported intermediate plate in the baja as well.

So do you guys think the tall ports, which are mismatched to the intake manifold, are helpfull in reducing reversion? Is that why Mazda did this? You know, Mazda stopped using short intermediate ports at some point. The '74-'75 3B engines found in REPUs had short ports. The '76 Cosmo had tall ports with a reversed runner manifold. My bro's '78 RX-4 wagon had tall ports with a short port normal runner manifold (that's the streetport with the surprising low end I mentioned above). And all '79-'85 1st gen 12As had tall ports with short port manifolds.

So some time between '74 and '78, Mazda switched to tall ports. The carb that came with the doner engine has features of a '76 Hitachi and different features from other years. It is certainly compatible with tall ports. Only the secondaries felt weak, but I only upped the jets to 145. It currently has 100/145 jets and 60/90 air bleeds allowing much higher RPM use than before. Those jets and bleeds are probably perfect for stock ports. :)

Maybe I'm thinking about this too much, but it seems to me that a port mismatch is a good thing, and I should use it to my advantage on the baja. Thoughts?

After debating with myself at length over the last couple days, I've arrived at a conclusion. I now know which parts I should pick put of my pile to build a nice 13B for this baja. :D

I'm going with the tall ported Y intermediate plate because it weigh less and the port mismatch from the manifold to the engine should reduce reversion. The engine will be unported for now with only the casting flash and harsh 90° edges smoothed, leaving a rough texture in the runners. The tall geared bug tranny will remain for now. Then when I can source a 3 or 5 rib bus tranny, I'll port the engine out to '74 spec. The shorter gearing will take care of any reduced low RPM torque as a result of the porting, and the extra strength will handle the engine's increased mid to high RPM power. Everybody wins. :)

Great Project, I Like Anything That Has A Rotary In It.

Now where should the radiator go?

That does look like one hell of a great project.

better get a well built trans to take the extra hp. are you going to run solid mounts or a berg interimate mount for the trans there is also a after market interimate housing to run a bug nose cone with the bus trans

Its a blast to do the rotary conversion, we did several back in the 80's and 90's.....

Friend of mine had a 12A in his. It was way cool.

Radiator was up front mounted similarly to how you see a V-mount rad on a 3rd gen. I think he might have had some louvers low on the hood to bring more air to the rad as his was a lowered street car.

I think he might have also used some kind of old 911 transaxle rather than the VW trans. Good luck.

broke7, I don't know. I think it has a beefed tranny mount. I'll try to get a picture when it stops raining.

Kathy, what type of oil coolers did you use?

Thanks everyone else.

It looks like it could be made beefier with a bellhousing strap.
https://www.rx7club.com/forum/attach...d=204642&stc=1

At least it has a front tranny strap. Will that be enough?
https://www.rx7club.com/forum/attach...d=204643&stc=1

I think the 13B is longer than a bug engine. Do you think there will be enough room for the engine pullies and a small exhaust system? I could always extend the push bar rearward if necessary.
https://www.rx7club.com/forum/attach...d=204645&stc=1

I'd like to put a radiator inside the nose. Maybe relocate the license plate to the front bar and cut out a nice rectangle for air.
https://www.rx7club.com/forum/attach...d=204644&stc=1

I had a sand rail about 20 years ago that I put a hot GTI engine in. I ended up using the stock engine mount at the end of the engine just to help the tranny a bit. I'd get a HD side plate for the trans axle("Rino" side plates I think they are called). I used to rev the water pumper to about 7500rpm but it only had about 140HP, it probably had the same amount of torque as the 13B though. Th tranny worked fine being stock except the side plate. Sounds like a fun buggy in the works.

I don't know much about the side plate issues of VW trannies. I was hoping to possibly trade the 1600 and tranny for a good bus box. Preferably 5 rib.

It also looks like the radiator can't fit inside nose. That is, the tall rads from '83-'85 1st gens like I was going to use. I'm not sure about the short radiators.

I'm also noticing my thoughts drifting over to my 20B and how much fun it would be in the baja. As impractical as that sounds, lots of people install heavy torque monsters in their bajas. Why can't I? Money, for one thing.

I can almost afford a 13B because it won't require any mods to the car other than a radiator up front. Speaking of which, it might be a good idea to ditch the bugeye front because there is simply not enough room for a radiator up there.

If I fabbed some headlight holders and a way to keep the hood closed, I could replace the bugeye nose with just headlights and a radiator. It would look odd, but function exceptionaly well. With cooling like that, I could get away with a 20B. :)

Of course it would need a real oil cooler. Not the beehive I was going to use with the 13B. How do I cool it? With a row of small computer fans? The shape of Mazda air oil coolers are perfect for mounting low under radiators, but not for most other locations. Maybe two stacked oil coolers with a 10" fan might work.

This project could easily eat several thousands of dollar quickly. We're talking suspension mods to handle the extra weight, upgraded A-arms, beefed transaxle and better CVs, definitely an engine cage tied into a main cage throughout the whole car to support the engine weight and strengthen the rest of the car.

I'm thinking too much. I haven't even reached the limit of the current setup. Well, I have sorta, hence the whole reason I'm brainstorming a rotary swap, but you know what I mean.

I think I should add an MSD and try to improve the VW engine as much as I can for now. Then when I get the rotary adaptor I'll use the 13B with the bug tranny or maybe get a bus tranny at that time. Then see how much I like it. Then if there is still a desire to go bigger and better, and if the 20B is still available (and I've gotten better at tuning the MegaSquirt), and if I have a few thousand saved up to do all the supporting mods, I'll consider it.

Jeff, I have to say that I admire your ability to make a plan to try something and do it. You seem to be more willing to try things you don't fully understand and go at it whole heartedly than most people go after things they know whole heartedly. I have much admiration for that.

I really would love to see some pics of what you are thinking about doing to the front end of the Bug though. I think that would be quite an amazing project, and I also think that a 20B in a Bug would be fucking nuts. A 13B would be a great swap, and in all honesty I think that is the route you should take; however, that is just my thought on the matter.

Regardless of whether or not you keep it a Bug motor, swap a rotary, or whatever you decide to do though, good luck on it and I can't wait to read the continued development of the car.

Thanks for the kind words. This forum is as much a creative outlet for me as doing the projects themselves. Even moreso in some ways. It's also great for planning projects and showing off what I've done.

Since the weather turned rainy here, I find I'm spending more time on forums. The SC on the RX-4 was the last project I finished before the rain. Right now I'm in the middle of beefing up some wood shelves in my garage to hold more weight. I was hoping to get a couple engines off the floor. There is a lot of stuff to go through and get rid of. I'm not looking forward to it (that's why I'm spending so much time on the forum today :) ).

If I wasn't planning a 20B swap into a 1st gen, the baja would definitely get it. Here's the situation that I'm in. I'm actively planning a 4 rotor 23A (based on 12A parts) with my friend for his 1st gen. I was doing a 20B NA in my 1st gen. We'd have a couple multi-rotor 1st gens to play with. The only baja around here that would even come close to accepting a 20B in its current state is this one. http://www.geocities.com/cd23c/cars.html#rebaja

As you can see, it's got all the 'beefed up' parts like the 5 rib tranny, engine cage which ties into the cage inside the car, a fuel cell up front etc. When last it ran, it had a tendency to overheat. The radiator is under the rear wing and doesn't get enough airflow. If he mounted the rad in the front nose area it would be fine. Anyway this car is what mine would need to be similar to in order to house a 20B. All it takes is money and time. I have niether right now.

As you can probably tell from reading all of this, I would really like to put the 20B into something that will be fun. Do you think a 1st gen would ultimately turn out to be more fun? I know I probably could afford the time and expense it would take; likewise for the 13B in the baja. I however couldn't afford a 20B in the baja at this time. I also couldn't afford to do a 4 rotor in the 1st gen (my friend will end up spending close to 10k, but the car will perform closer to a 50k sports car we think).

I do happen to have a GSL-SE oil pan sitting here, which could easily go onto the 13B, which would then easily fit into the 1st gen, but it is not the sole reason to go 13B in the 1st gen. My friend's other 1st gen has a ported early style 13B with 5" SC, '86+ rotors, aluminum flywheel and the RB dual pipe exhaust system. It screams! My 13B has the heavy early rotors. Plus I'd have to port the side plates and rotor housings out really far. It won't perform as well as his no matter what I do, unless I got some '89+ rotors... Blah.

Since I'm just starting out on both projects, it seems the best approach is one of practicality. I don't want to spend the next year just getting these things to run. I want to do them now, or as soon as possible. When you're doing as many projects as I am, it starts to feel like a job instead of a hobby.

Not looking forward to those shelves...

In all honesty I think that FB with a 20B would be a lot more fun. I couldn't imagine a Beetle ever being able to handle as well as an FB no matter how much modifying it had done to it, and the suspension work it would take to be able to handle a 20B in an FB would make it that much harder for the VW to compete with it.

I understand what you are saying about too many projects at once. I tried taking on two FB projects at the same time and ended up running short on cash for both (but that wasn't just the fault of parts and what have you, I had a lot of other things going on as well). I honestly think the 13B would be much more suitable for the Beetle than the FB, and that is mainly because I think the 20B would be too much motor for the car. More specifically, the handling would never be able to match the engine's performance unless you didn't have any porting or anything done to the motor and took the turbos off.

That however goes back to the FB's side where I think the FB would still make much more of a fun car. The Beetle can make ample amounts of power with the 13B, and if you are going to put a larger-than-two-rotor in a car, don't you think it should be a car made for the rotary in the first place?

I also can't wait to hear the finished product of the 23A. Something that has always intrigued me is building custom made more-than-two-rotor rotaries.

That is just my two cents on the matter though.

Yeah, you're right. For a street driven Beetle anyway. Even 12As do very well. Since mine will be for street and some offroad, a non ported 13B with exhaust ports which peak at low RPM (late opening, like a GSL-SE as far as I know) ought to do it justice.Yes and no. Of course I like a rotary in anything so I'm biased.

I can look at it from one perspective in as much as nobody out there has ever done a succesful rotary baja to the best of my knowledge, so why should I do one if it's not a tried and true swap? I guess because I have something to prove. While most baja people will either build air cooled VW engines or get any of the popular water cooled engines like ecotech, a V6 or some other 4 cylinder, the rotary baja simply doesn't exist. I've kept my eyes open. There are none. With one exception.

My friend's rotary baja has only been driven a couple miles since the conversion and wanted to overheat and had other problems. I guess it's not really an exception because it has not yet proven itself reliable. I think we'll get back to it after his 4 rotor is done.

He started off with perhaps not the best engine for the job. It's a '74 REPU based 3B 4 port 13B complete with short primary ports and small exhaust ports on the outside, with a streetport job on the inside. I have an identical engine from my REPU which I could try in my baja. The only difference is mine does not have a port job. Good candidate?

His engine still has the stock cast iron waterpump (added weight). He installed some VDO guage senders and there is the potenial for a leak at the water temp sender. I suggested a better location for it, but it's extremely difficult to work on the top of the engine with the radiator and misc stuff blocking access up there. The exhaust consists of the Racing Beat dual pipe system, minus the primaflow muffler, and a megaphone acting as a stinger with a supertrapp insert. The long primary exhaust does help with low end power but it was hideously loud without the supertrapp insert. With the insert it acts like a cork hurting power but at least people won't call the cops. The tranny has welded spiders (Lincoln Locker) making driving on the street a challange (it tends to go straight when you turn the wheel). The Holley carb doesn't have the low end grunt of a stock Hitachi. The streetports make low RPM driving a chore. All the added weight hurts performance. It has a full weld-in rollcage (weight, but necessary), 32" tires (weight, unsprung), two batteries (weight, one is mainly for lights), a 3" body lift kit (kinda cool, but I don't see a need for it), extended travel suspension components (cool, not sure how much it hurts performance due to its increased weight and size).

Comparing that overbuilt baja to mine, and my current plans for it, at first thought, they seem as though they'd be like night and day off road; his the superior car. Then again, I know bajas can get to places only the big lifted 4x4 guys dare to tread, but do it faster, even on a healthy bug engine. :) For one, the lightness helps. So less power required to move it. It doesn't sink in the mud as deeply. The engine over the driving tires gives great traction. My friend's baja will need a lot more power to overcome all the added weight while mine should happily chug along with less to go wrong.

Yeah, puting the 20B in my baja sounds like it would be a mistake. Now in my friend's baja, the 20B would be rather awesome because it could support it. He'll just have to get one (or maybe build a fake one out of 13B parts, but figure out how to do side ports if the usually required peripheral ports suck for offroad).

stay with the vw will be cheaper in the long run and in my opnion better in the woods the best part is it is so simple less parts to break mate a 3 rib trans to your 1600 or up to a 2000cc and it will drive like a different car much better off road due to lower gearing and is a heavier trans in the woods the bus trans is the only way to go much stronger than the car trans even modded. vw trans aren't cheap the close ratio box for my 68 cost over $1700 but thats for a 200 plus hp street legal drag car that should run mid 7's in the1/8 mile i also have a 84 rx with a 13b half bridge so i do like rotarys but would rather have a vw engine in the woods DON'T WELD YOUR SPIDER GEARS OR RUN A LOCKER ON A VW RUN REAR DISCS AND TURNING BREAKS MUCH BEETER OFF ROAD YOU CAN TURN THE CAR ON A DIME

While I agree with your pro VW views, and appreciate your input, I must make it clear that for me, switching to rotary will actually cost me less in the long run. A little more at first with the adaptor, but after that initial expense, a rotary will be far cheaper and pay for itself in short order.

I can build the 13B described above for $350-$400. An ACVW with similar power and torque would come closer to $1675-$1800 or more depending on the mods. That automatically assumes the engine has been hopped with better than stock internal parts to handle the increased power, RPM etc. Then the reliability comes into question. What's more we're talking a 1776 or bigger up to 2000, like you said. That means I couldn't even reuse my case, heads or any other parts.

I've invested my time in rotaries. I know enough about VWs to know that the engines, while unique and different, aren't for me. There is plenty that can and WILL go wrong with them, not to mention the time spent in regular maintenance, which I don't feel any particular passion for. Sure there's less moving parts than in a water cooled inline 4 cylinder, but many times more than in a rotary. The valves need adjusting what, every 3000 miles? Points that need adjusting periodically and caps and rotors that need replacing every now and then are obviously regular maintenance items, but a rotary swap can eliminate all of it. Seriously, you can drive for many thousands of miles and not touch it other than oil changes. Not to mention the cost per HP. It costs a small fortune to make big power with VW engines. Then of course the reliability goes down; not a good idea for a woods baja, which this will be. In my opinion, the extra fuel consumption of a rotary is made up for by the almost zero maintenance required. Plus since I know rotaries in and out, I feel more confident treating one hard. I'd be affraid of breaking a VW engine. It's the mental edge I have with rotaries that I feel further qualifies this swap.

From the standpoint of cost+time+knowledge+future maintanence, the final sum adds up to a big win for the rotary and a dismal second place for the VW. And for the purists out there, it's a baja. It's already been hacked up. And everyone whom I've contacted so far about their rotary swaps has said it's been totally worth it. Yes, even one baja guy so far (thudknuckle). He totally loves it.

I finally got the manifold. One or the other. They're both great. :D

https://www.rx7club.com/forum/attach...d=230589&stc=1

The 13b will fit with lots of room in your baja bug, when I built mine about 20 years ago it was for the same reasons that you are building yours "cheap power" I ran my radiator mounted to the engine cage and adapted a metal fan that I found at the wreckers you have to twist the fan blades 180 to get the air to blow back through the radiator. I also ran the stock tranny against everyones advice the only problem with doing that is the gearing try 38 mph in 1st, 68 in 2nd and when I hit85 in 3rd the front end would start to float around baja bugs are not exactly aerodynamic. I built a very short header and went directly into a corvair turbo muffler, it would last about 3 months before it burnt out. I also used the kennedy adaptor plate and clutch and I used a chevy delco altenator in place of the stock one as it has an interal voltage regulator and maid the wiring a breeze.

Welcome to the forum!

I like your solutions. That's what these projects are all about. Well, there's the fun aspect too. :D

I'd love to get a 3 rib tranny, and probably will at some point, but if I don't, I know the 13B can handle the taller gears of the stock one since it has more torque than the 1600 everywhere in the RPM range, or that's what I've been lead to believe. It seems anything has more torque than the current 1600 though. It's tired. :)

Interesting that you adjusted the fan so it would push instead of pull and kept the radiator in the back. I'm still debating radiator placement. With the small bugeye front end, it doesn't leave me with many options for front mount, unless I ditch it and go for wide eye fenders or mount the headlights in pods kinda like street driven sand rails, but below the fenders etc.

I'd prefer the radiator in the back because it seems easier in the short run. I'd have to move the fuel cell up front to try to offset a little weight.

I have two old Rotary Engineering glasspacks from about 1991. Much of the glass material has burned out of one but I think a short header and them both inline would reduce most of the noise. If it's still too loud I could add a stinger with an insert if they're not too restrictive. Would the stinger interfere with the radiator? Probably.

What did you do about an oil cooler? I could use an air or beehive type. Air type, if I put the radiator in the back, and if the exhaust is quiet enough without a stinger; and beehive if I need to mount the radiator up front. Or a combination of things. I won't know until I get to that point.

I see you used a non stock internally regulated alt. Fortunately I have a stock '84-'85 internally regulated alt to throw on there. It's the kind with internal fan (a safety issue more than looks, but it does look nice). I'll also upgrade the ignition to DLIDFIS.

I think a KEP 1700 pressure plate would be enough. I believe the PO already installed one. It feels great with the 1600 but the bowden tube is a little too short and causes a chatter every now and then. It'll get dealt with when the tranny swap happens.