pope_face

I apologize in advance if some of this stuff doesn't make sense to other people... I'm too lazy to rewrite this for this forum, so I'm just copy/pasting it from my other forum to keep you folks in the loop...


Here's the deal: Take one 1970 Datsun 521, add a Wankel rotary from an '85 RX-7 and four-speed auto transmission, and redo the interior to end up with a 521 RST (Rotary Sport Truck).

The Truck:


1970 Datsun 521 (North American Market)


The Drivetrain:

(No pics yet, will add them as soon as I pick up the engine)

Engine: 1985 Mazda Rotary 12A

Transmission: 1986 Mazda RX-7 Four-Speed Auto

Final Drive Ratio: 4.88:1 (Stock Datsun 521 w/ J13)


The Interior:

Nardi wood steering wheel on Momo hub
Old-style Recaro racing seat
Wood dash w/ plain round gauges (Styled after 70's British cars)
Dash air vents
Stock switches
Four-speaker audio system w/ sub and hidden headunit.

The Exterior:

Flat black paint w/ red & white scallops
Red stockers w/ stock chrome hubcaps
Custom grille
Eurolite 5.75" round H4 single-headlight conversion in stock low-beam position
Mercedes or Bosch fog lamps in stock high-beam position
Bosch or Hella bumper mount driving lamps
Bumper mounted motorcycle turn signals
Rear roll pan w/ integrated taillights


Interior sneak peek:



I know, it's kinda dirty inside, but that's what I've got so far. Nothing's changed on the outside yet (as I can't get damn rusty screws out). The Recaro will stay if I can shorten the steering column and get a quick-release hub. If not, I'll use a '69 Datsun 510 seat like on the passenger's side.

Questions, comments, concerns?

Viking War Hammer

iTrader: (8)

i like the paint job

Jeff20B

iTrader: (13)

It looks like you've made progress even if you haven't .

pope_face

Viking: Thanks, it was the first reason I wanted to buy it. (Other than the fact it was a Datsun)

Haha, thanks Jeff... I suppose it is moving forward a bit from the last time I've posted here. At least I've got most of the interior/exterior stuff figured out.

I forgot to mention that I'm considering either a moonroof or ragtop... I've got the material to put in a ragtop, so I just need to figure out how to do it, or find a cheap moonroof kit on craigslist or something. I'm also on the hunt for a used four-point harness.

I've gotta say, I love this truck, but the size makes it a hell of a lot harder to work with... everything I do has to get test-fitted and modified about four times before it fits well enough for me to commit.

But, so far I've got most of the interior stripped... the dash and steering wheel have been removed, the seats aren't bolted in yet, and most of the wiring is off to the side until I start playing with it. Some of the wiring has been Mickey Moused, so after I get the engine swapped in and running I'm going to start working my way through everything. I've got a spare wiring harness and a couple manuals, so I can check where everything goes. I'll have to redo the wiring for all the lights anyway in order to run the single-headlamp system and fogs. The Recaro came with a pair of sliders, although the idiot that had it before me decided to weld the sliders together so they weren't parallel... I'm going to have to grind off the welds and line everything up before I can bolt the seat in. But, all in due time.

teddyrx2

iTrader: (33)

nice project..where are you with this?

datsun1200

Yeeeeeaaaaaaaaa a datsun......

vwfred63

gotta luv those old datsun trucks

teddyrx2

iTrader: (33)

any word from this guy?

pope_face

Here's a word from this guy: I'm baaaack...

Wow, five years since I've "started" this. Maybe I should've waited to make it "exactly" five years. To be honest, I haven't really done anything in that time. But, I've finally got the time, space, and inclination to finally finish this off. However, the engine's been sitting in my garage for that time, and I'm a little concerned about it's potential condition... I was reading through the 1st Gen FAQ earlier, and found out that a busted apex seal will destroy the housing. I think the engine was filled with fluids before I got it to prevent it from rusting, but I'm not certain, so I have no idea what condition the seals (or surfaces in the housing) are in.

So having said all that... Should I be tearing into the engine to check the condition of the seals/gaskets/all that, and make sure that there's no rust or pitting in the housing? The engine hasn't been installed yet, so I'd rather address any potential issues now, rather than getting it installed and finding out I've got a problem.

I also want to clean up the rat's nest, install a mechanical linkage for the carb secondaries, and maybe do a mild port/polish (just to clean up the ports a little and match them up to the manifolds), so the engine will be on a bench while I address that. I just wasn't sure if opening it up was a good idea, and I don't know how easy it is to mess something up in these engines.

I'm also considering getting into the transmission to check the condition and clean it up, but I'll leave that until the engine is sorted out. I wouldn't mind converting it to a semi-auto, if I could... I'm sure there's info somewhere on what lines need to be blocked off to prevent the transmission from shifting on its own.

Anyway, I appreciate any input. Hopefully I'll be sticking around longer this time... I actually want to get this done and get the truck on the road.

pope_face

Well I had a chance to go out to the garage and get a good look at the engine today, and I'm pretty pleased with what I saw. I took a look down the carb, and it looks reasonably clean. There's a few bits of dust/dirt, but I'll give it a good clean before I install the engine.

I cranked the engine by hand a couple times, and it moves without much trouble... I pulled the spark plugs to check them and prevent compression while cranking the engine, and they looked decent. They were black on the end, which isn't good, but they were oily, which indicates the engine had been filled with fluid before it sat. As I cranked it, I started getting some oil spraying out from the spark plug holes, and formed little puddles in the spark plug holes. The oil looked good though... Clean and clear, with no debris or anything in it. When I turned the engine around to get a look at the intake, I found a little puddle of oil under the exhaust, and it was leaking out of the exhaust manifold.

I put the plugs back in and removed the intake, and the runners look good. The ports into the engine look decent too... A little darker in a couple spots, but no signs of rust or anything. I cranked it over again, and started getting oil coming out of the intake ports. I also wanted to see what the compression sounded like. I got a bit concerned at first, because I heard a "POOF-pfft-pfft" as I was cranking it (by hand). However, that repeated twice for every revolution of the crankshaft. I did a quick lookup once I got home, and apparently the rotors turn at 1/3 the speed of the crankshaft, and each face goes through a compression cycle per revolution, so I'm thinking that the "POOF's" were the compressed air escaping through the exhaust, and the "pfft-pfft" were either the intakes or some leakage.

Anyway, I took a whole lot of pictures, and a video of me cranking the engine by hand (you can kind of hear the "POOF-pfft-pfft" in it), so I can post them up if anyone's interested. So far, it looks like the engine may be OK to just go into the truck, although I'd love to get a look at the condition of the rotors and housings before it goes in. Ideally, I'd like to check them without having to pull the housings apart, but I may need to get a fiber-optic camera and insert it through the spark plug holes to achieve that (unless someone has any other suggestions).

invinciblejets

Post up the video/pics....ohhhh and buy a manual gear box

pope_face

I'll get the pics up eventually... I just realized the other day that the easiest way to get a look inside the housings was to pull the exhaust manifold and look through the exhaust port. Unfortunately, I didn't do that the first time around, so I'm waiting until I have a chance to get some pictures of the rotor (and the inside of the housing, if my camera fits) before I post the rest of them up.

I was hoping to get some work done last night or this morning, but no such luck. Ended up running out of time. I finally picked up an engine stand (so I can stop dragging the engine across the floor), but I don't have the right bolts to mount the engine to it. Unfortunately, I won't have time to get the right bolts and do some work until next weekend.

As for the transmission: As much as I'd love a stick shift, I can't drive one. If I could, I probably wouldn't be bothering with an engine swap right now... The truck has a working engine and transmission, but there's no autos available for that engine, so a swap is my only choice.

Anyway, I'm gonna spend some time poring over the FSM to figure out what I should pull from the engine, and what should be kept (mostly from the rat's nest). So far, I've figured this out:

- Keep the leading/trailing vacuum advance solenoids... I'm keeping the stock distributor for the time being, and I assume these control the timing of the ignition based on RPM.

- Ditch the switching solenoid and relief solenoid. I've already pulled the air pump, as I'm not planning on running cats, and as far as I know these two solenoids only relate to the air pump.

- Ditch the shutter solenoid, although I'm not 100% sure on what it does. It seems to have something to do with the emissions and choke control, but I'll be running a manual choke anyway (I don't know if these cars ever came with an automatic choke).

I'll also be swapping the carb over to mechanical secondaries... Not for power necessarily, but to make it more reliable. Besides, mechanical linkage > vacuum controlled in my books. The Nikki is way too bulky anyway... I wonder if I could get some motorcycle carbs to work. That might be a fun project for the future... Custom intake manifold with separate runners for each housing, with two motorcycle carbs per intake (one primary, one secondary). I was going to do ITB's if I'd ended up building a 4-banger instead of a rotary, so this seems like the closest rotary version of that.

There is no A/C, so that solenoid is going as well, which leaves me with only two solenoids from the original rat's nest. Hopefully that'll keep the engine running smoothly, without too much loss in power/mileage.

pope_face

Alright, so I should be studying for an exam, but I'm thinking about the engine, so I thought I'd take a break and share my thoughts. I don't know if anyone will have any suggestions, but it's nice to get things down on "paper".

So, I'm not one to leave good enough alone, and I'm considering some sidedraft carbs for the engine. I mentioned ITB's above, but I realized I wasn't being exactly accurate... I don't intend on doing EFI, but I do like the idea of independent carbs per cylinder. However, since this isn't a 4-banger, I really only need two carbs to achieve that.

Now, I did a bit of research, and apparently the stock Nikki puts through about 300-320 CFM. So, technically, I would need two carbs that can handle that. However, I also read that the Nikki is set up as a 4 barrel because the engine only needs a given amount of flow at low RPM, but a lot more at high RPM. Thus, the primaries and secondaries. If you have only one barrel per rotor, you can either have good performance at a low RPM (with a small carb), or good performance at high RPM (with a larger carb).

I'll skip all my logic (I'm sure it's pretty straightforward), but in order to have good driveability across a wide range of engine RPMs, I'll essentially need primaries and secondaries for each rotor. I also read that two of the intakes pull in less fuel than the other two (I assume it's the tall, skinny ones in the center), which means that they don't need the same jetting as the other two ports.

So, I figure my options are:

- Two, two-barrel sidedraft carbs (like Webers or Dellortos), one for each rotor;
- Three, single-barrel carbs (one each for the front and rear intakes, and one split between the two middle intakes)
- Four, single-barrel carbs (one for each intake port)
- Four, single barrel carbs (one as a primary, and one as a secondary, for each rotor)

A pair of Webers or Dellortos would be the easiest to set up, but probably the most expensive, and it's been done. The three single-barrel carbs would probably work, and I could either run the front and rear as primaries, and the middle one (feeding the middle intakes) as a secondary, or run all three simultaneously.

The four carb solution would be similar: Either run primaries and secondaries, or run all four simultaneously. I'd also have to sort out whether I want four carbs of the same size, or if I want two larger ones and two smaller ones.

In any event, this is more of a thought exercise than anything else... I'm not planning on doing this until the car's already running with the stock Nikki, but I need to do some custom exhaust work anyway, so I may as well consider an upgraded intake. Plus, it gives me a chance to work on some welding and fabrication.

Jeff20B

iTrader: (13)

You're not gonna do four single barrel carbs. Nobody does that. Not even three and rarely two.

The stock Nikki is actually the easiest to set up. It just requires you to take the extra bulk off that's not needed. Also pull the shutter valve from the manifold and cut a channel to match the other side. I've done a few and they're really easy.

https://www.rx7club.com/attachments/...mani-nikki-jpg

https://www.rx7club.com/attachments/...-mani-mani-jpg

The thread: https://www.rx7club.com/1st-generati...i-mani-637323/

Just one update. I recently swapped this carb back to stock 92 primary jets because the 95s were not needed and ran kinda rich.

Like I said, easiest to set up and runs like a champ to this day.

pope_face

Jeff: I appreciate the input. The Nikki will definitely stay for the time being. I want to get the engine installed and running properly before I start messing about. I appreciate the link to the thread... I've got that picture that tells you what to keep and what to ditch to convert the Nikki to mechanical secondaries (I can't remember who made it though), so I'll be following that. I've already pulled the air pump, but I'll make sure to notch the carb side of the intake as well.

Do you happen to have a picture of the other side of the air pump block of plate? Is it just a flat plate, or does it have machined grooves in it? The reason I ask is that it seems quite thick to be just a flat plate, and I wasn't sure if any of the ports needed to be connected together. Either way, I'll probably be making my own, so I figured I'd ask.

As for the multiple carbs: I know it's not done, which is why I'm considering it...

I figure the triple or quad carb is the best way of doing it... I was doing a bit more looking around, and I read that the two center ports (tall, skinny ones) are the primary ports, and the other two (on the front and rear plates) are the secondaries. If I run one (or two) smaller diameter carbs to the center plate with some long runners, then I should get some decent low-end torque. Then, larger diameter carbs with short runners for the other two intakes as secondaries.

But, this is just some thinking about what could be. Considering the entire project is just me pushing my boundaries, I'm keeping my options open. I'm already considering a true dual exhaust, although I think it'll be loud as hell...

Jeff20B

iTrader: (13)

Flat metal. 1/4" aluminum can work. Or 1/8" steel (or aluminum). Whatever. Actually you would not need it at all if you blocked the ACV port in the intermediate plate itself. This also keeps exhaust heat out of the manifold. You can also install some 20mm freeze plugs in the rotor housings. This keeps coolant heat out of the manifold. I call these steps the cool manifold mod. Totally worth it. I'll be doing exactly this on a 12A that's going into a cream colored 85 GS soon.

Just be sure to explore the small holes and see where they go if you don't end up getting or making an ACV block off plate. You can test them with compressed air. Either thread a screw in there or use some quicksteel or other hardening putty.

These types of mods are probably my favorite thing about the FB engines. Well, the 12As anyway. I don't care for the 6 port EFI stuff (but I love the old school 4 port carbed 13Bs!).

True dual? Again it isn't done often. It's better to study what the engine wants and recommended by others who've done the research; RB recommends 120 to 125 inches for a long primary before it collects but we don't have that kind of room. however we can half-wave it and go to 60 to 62.5 inches. You also want to collect to 2.5" while keeping the primaries a thickwall 2". You also want to add a presilencer to each primary. The rotary is an inherently loud design and the long primary just makes it louder. But I've succesfully built a quiet long primary for a couple of REPUs that collects at 61 inches and are very quiet. You car, being a 510? Will require nerves of steel and a cast iron stomach because I know about the small hole you have to push the pipe through in the rear suspension. So I'd recommend hogging the hole out as large as others have done, and indeed going with a long primary with two custom made presilencers, then keep it dual until the suspension hole. Then collect it down to 2 1/4 and on into a very agressive magnaflow - the biggest shell size you can get with an offset/offset in 2 1/4 that will fit under the rear apron(?) bumper. Or if 2.5" is an option, do that, but 2.5" will be louder. Just a word of caution about that.

pope_face

Jeff: I went through and read your entire thread about machining out the manifold to match it up to the side that's already machined. I was planning on doing that originally, but I noticed that you started talking about the carb spacer. You mentioned that you're running the stock spacer, without cutting it out to match the machining in the intake manifold. You also mentioned that machining out the spacer would likely cause an increase in HP in the upper RPM range at the expense of torque in the lower range.

So, having said that: Rather than machining out the one side of the intake manifold to match, would filling in the other side result in an increase in torque in the low range, at the expense of upper range HP? I assume that you'd essentially be creating four independent runners: One for each of the primaries and secondaries. The way you have it done, you've got essentially two runners, each fed by two barrels.

Just some food for thought... I don't think I need a whole lot of torque (I think my gearing will be pretty low anyway), but it might be curious to see what going the other way would do in terms of performance.

I will definitely be blocking off the coolant ports to the manifold though... Thanks for the tip. If I can find a sheet of phenolic material (or some other suitable spacer material), I'll look into actually separating the intake from the block. The increased runner length might help with the low end torque, and it'll insulate the manifold from the housings. I will definitely be sure to check the other holes too.

Thanks for the info on the block off plate too... I'll just make my own probably.

I agree about the carbed engines... It's a shame that Mazda has discontinued all the parts for our engines, but I'm sure someone will come up with a carb modification for the newer rotaries at some point...

Jeff20B

iTrader: (13)

That thread is also pretty old. I left the spacer stock. No reason to mod it other than to trim off the excess outer edge because it's big and in the way. Think about it: cooler manifold = no need for the phenolic heat effect shield anymore.

And fill in the ACV port in the engine. Nobody around here believes it's necessary to do. I think they're all a bit screwy. You see the coolant is there to keep the manifold COOL when exhaust heat is flowing during some running conditions the ACV experiences. And at all other times it pulses up into the manifold and carries carbon (and heat) with it. So you end up with a very hot manifold if you add freeze plugs but don't fill the ACV port. Just look inside your manifold and you'll see a bunch of carbon. How did it get there?