4-Rotor FB Build (side ports!!)
 

12A kit from Jeff Bruce after it arrived.
https://www.rx7club.com/forum/attach...1&d=1208196459

Famous Jeff Bruce (Precision Engineering) shaft. Top notch machine work here. If you lack the means/know-how to machine something like this yourself, get it from them.
https://www.rx7club.com/attachment.p...1&d=1324577597
Looks like 4260 on the front CW. But we told him 4269 grams rotor weight... Or maybe 4260 is the standard weight offset when spin balancing a 12A with 83-85 rotors... It must translate over to a 4 rotor the same then? See here. http://www.who-sells-it.com/cy/mazda.../page-148.html
And you can kinda see the marks left over from the V-blocks they used. I'm not worried about it - it means it's been dynamically balanced.

Test fitting everything. Had to open up the front slot a little, and hog out the front CW hole. It warped during welding.
https://www.rx7club.com/attachment.p...1&d=1325183589

Up Up, Down Down, Left Right Left Right, B A, Select Start. :D
https://www.rx7club.com/attachment.p...1&d=1325183596

Turns out that first rotor we weighed was too rusty to use, so I needed to come up with another that's close enough to get started...

Weighing, drilling, weighing, drilling, weigh- ah, there we go.
https://www.rx7club.com/attachment.p...1&d=1325183589

it still has an oil slinger
https://www.rx7club.com/attachment.p...1&d=1325183589

bye bye. #1 and #4 get removed.
https://www.rx7club.com/attachment.p...1&d=1325183589

Finally done!
https://www.rx7club.com/attachment.p...1&d=1325183589

That's a My Weigh 7001DX Multi-Purpose Digital Scale accurate to 1 gram which is all you need, really. I've got a ten gram tolerance. Close enough to 4269, too. :D

Side ports, baby!

This isn't a mockup. These are good housings that just need a cleanup and porting.
https://www.rx7club.com/attachment.p...1&d=1325185093

Multi-hole bearings. Good idea here?
https://www.rx7club.com/attachment.p...1&d=1325185093

Actual good 12A housings in this day and age. Incredible.
https://www.rx7club.com/attachment.p...1&d=1325185093

Jeff Bruce modded intermediate plates
https://www.rx7club.com/attachment.p...1&d=1325185093

three oil return slots (I think John Hujben needs to make his bigger).
https://www.rx7club.com/attachment.p...1&d=1325185093

three really big oil return slots
https://www.rx7club.com/attachment.p...1&d=1325185100

Final installment for today (unless I think of anything else).

Jeff Bruce tapped stat gear.
https://www.rx7club.com/attachment.p...1&d=1325185949

The long tube it comes with. BSP threads on both sides. I've got the tap, but no fittings. So to feed oil, I'll probably use This T adaptor and drill the 1/4" NPT plug for 1/8" BSP.
https://www.rx7club.com/attachment.p...1&d=1325185949

Then plumb it off of the oil filter pedestal. Like this.
https://www.rx7club.com/forum/attach...1&d=1208716482

According to Jeff Bruce, the mod isn't entirely necessary, but a good idea. Glad we had it done.

The other pictures in thumbnail form are from Scoot's PP engine. Enjoy.

AWESOME. how much did the shaft set you back if you dont mind me asking?

You better finish this build!! :D

rotarycrazy, this will be the build thread. All extraneous info can be found here, but you'll have to dig for it. ;) https://www.rx7club.com/1st-generation-specific-1979-1985-18/ghetto-4-rotor-build-638177/

twinkletoes, I just started! Oh, I see what you meant. It didn't get finished before not from a lack of funding or time, it was because going peripheral was a bad idea from the start. The exhaust we had in mind wouldn't work. The weber carbs- yes, we were going to go carbed! Having researched this subject way too much, going EFI is really the best way to run p-ports. But the owner isn't down with electronics so it's carbs or nothing. That's an extra 1400 to 2k right there. And the time required to learn and tune one let alone two is... hurting my brain. We've had enough challenges with PercentSevenC's DCOE to make me not like them. And he's going EFI on his next motor so there you go.

Everyone goes p-port because they HAVE TO. 86+ intermediate plates have tiny ports. No good for secondaries. Or if going semi-pp, requires a really horrible intake manifold, and you can still only use the primaries. lol Some have done it, but you still have the large PPs that make weird turbulence and mess with the idle even while closed. But you still require a big loud exhaust for the PPs to breath making them athsmatic on the street when you have to choke them down. Add a cutout? No thanks.

One tune. One quiet exhaust configuraton. Done. Happy driver. Invisible to cops. Yay! :D

Side ports-only is uncharted territory. I don't know of anyone who's ever done it. Will it be smooth as a V12? Smoother? They say the 20B is like a V12...

And it's not about HP and torque. If I wanted power I'd build a ported FD with a large single and lots of boost. If I wanted torque I'd go 20B with a really large single and not port it. But it's not about HP and torque. Everyone does the same stuff over and over. Boring! Why do you think so many finished projects go up for sale after they've been built? They lose the fun factor or something? You never get your money back. And don't get me started on the V8 swapped 7s. If they were so awesome, why sell them? The fuel consumption is about the same as a rotary, so why not drive it daily? See where I'm going? You modded a car so much it lost something. Sometimes stock is better. Or maybe near stock (I hate 30 pound flywheels!).

All the little subtle things like a too-light flywheel, heavy grabby clutch, loud exhaust, bumpy ride, constant watchful eye on temp gauges (for you FD guys!). It's all enough to make you want to drive that comfortable quiet gas sipping Tercel more often. But those are not driver's cars. You hate yourself twice; once for driving the boring-mobile and again for wishing you hadn't modded your 7 so much.

Ok we know the orginal RX-7, the SA22C, was an excellent driving car. Complete with its (ghastly) 30 pound flywheel. So how do you think they got up past 100k miles in stock form? As gutless as they were, and all that? Because a team of engineers came up with the right compromises to make them work for most prople. And I've got to admit a stock 7 is pretty nice. The Nikki works well enough. The brakes and tranny are decent. And sooooo much better driving than any econobox.

Then I've read about people's most regretted mod & DirectFreak's over-built car etc. I'll learn from those mistakes.

So that's why I'm going side port. It's not really what you asked, but I'm sure someone would have.

jesus Jeff.... and i still am hard pressed to even get a 3 rotor client!

karack, this is the over-driven oil pump sprocket.
https://www.rx7club.com/attachment.p...1&d=1323896582
Just a quick and dirty to see if the pictures in my head would work in reality. So far, yes. Kinda based on granny's info to drive it 1:1. They had to mod two stock chains because no one had the odd spacing Mazda used. But I test fitted an FC chain and it looks like it will work. I set it on an already assembled engine to sort of check. Looks good. I'll need to stack a mockup and test the length for real. I wasn't about to remove the sprocket from the pump in the picture... I also can use an old school chain tensioner if needed (if I use an R5 front plate, that is).

Lightened RB race pressure plate.
https://www.rx7club.com/attachment.p...1&d=1323896582
It was old, I didn't have anything to loose. I might not need it. It depends on how much torque this thing is making.

Let's see... stock 12A is like 101HP at 6k and 100TQ at 4k. Is that right? So you add those up and you get 200 foot pounds. Not bad. But torque doesn't simply add. It actually multiplies. So we'd be closer to 250 torque.

Please correct me if I'm wrong!

2 webers could easily run 2k, once you buy all the jets and venturis and air filters and stuff. and getting both carbs to do the same thing will be a headache too!

if i were arghx i'd post the engine smoothness graph (there actually is one), the 4 rotor might sound like a v8, but its smoother....

Interesting, I've read your old topic front to back a few times, nice to read your moving on.
Are those tallport 12a intermediate housings hard to get?

And about the oil slots near the modified stationairy gears, could you do me a favor and measure the length and width of the slots at the side where the stationairy gear teeth are? Like so:

https://lh6.googleusercontent.com/-9...Dimensions.jpg

I'd like the compare the flow area so I know if I really need to machine my slots larger.
To be honest I'm sortoff jealous. You've got the e-shaft and all that sorted, and I like the side ports. You can always go semi pp if output power is a bit dissapointing.

Speaking of two carbs, I haven't posted my intake idea yet. I'll use two Nikkis. Stock FB manifolds. The middle intermediate plate will be the secondaries so the manifolds will need to be modded. Since I can't weld aluminum I'll have to take the engine and a couple manifolds to someone who can.

Or better yet get the engine running on primaries only. Then DRIVE it to someone who can weld aluminum. I'd just need to block all four secondary ports to get it running. Easy enough with a couple of spare manifolds you don't care about. Fill the unused runners with putty and block the middle intermediate ports with a steel plate held on by a couple of bolts threaded below the ACV port. 8mm x 1.25 to keep it the same as stock. Maybe one small 6mm x 1.00 above. The secondary fuel jets in the carb can be swapped with some filled with solder then thrown away. I've got lots of 160s and 92s.

Sure John, give me a minute...

W varies due to the curve but edges are 2.9mm and middle is 3.5mm

L is 17.6mm

I'm kinda jealous of you and tegheim. You guys have actual machines to play with. All I have is a drill press. That's how I manually machined down the teeth of an FC oil drive sprocket and cut off an FB pump sprocket. Even the welds are nasty. But at least it's sorta heat treated for strength like the stock drive sprockets are. Stock pump sprockets aren't treated and tend to wear in high RPM engines. Since this will be over-driven, it may wear quickly as well.

Tall Y plates are fairly easy to find if you do a lot of 12A stuff. Tall R5 plates are also available but be sure they're the later nitrided type.

I used GSL-SE intermediates for the motor mount studs. I wish they had tall ports but I'll work with them as much as I can. But if I ever go EFI, the bungs are already there. Just don't port them too big to keep velocity up for the injectors.

Seems like you've got around 165mm^2 of area at that point for oil to flow through and I've got 135mm^2, ah well, guess I'll make the holes a bit bigger. Thanks!

Woah, didn't notice the overdrive gear, you did that with a drill press? I'm actually impressed!

Thankyou! Yeah I think it's accurate to .1mm. But even so I'd like to use an already broken-in chain and a tensioner to take up the slack.

I adjusted chuck speed to max (3500 I think) to grind the hardened teeth. I held an old aluminum oxide grinding stone from a bench grinder. It threw sparks everywhere. :D Then to cut the bell section off the pump sprocket, I went the slowest speed like 200rpm and held a hack saw blade against it for a while. Higher speeds dulled the teeth. Lower speed kept everything cool.

One suggestion about your holes. Can you make them wider? Or oval? Going too big in diameter will obviously weaken the ring.

Im so jelous jeff. It looks awesome. Now ur gonna have to change ur name to jeff24a ^_^.

Great points and info Jeff! I can imagine the stress of tuning two carbs hahaha.

I've been thinking of taking my turbo car and making it a streetport/bridgeport 13b with a 48 IDA carb for simplicity and reliability. I love the boost, but I also dont love seeing my car sit in the garage. I'm planning to do another shot at the turbo and get it right with the tune this time, but going NA again has been lingering in the back of my head...

..and howd you know I daily drive a Tercel :D and that I love/hate it too :lol:

a three rotor NA would be the best compromise..

For some reason "Tercel" popped into my head as the example econo box to make fun of. I had no idea you drove one. Then again if you follow any of David Wilcock's stuff, it stands to reason I must have picked up on it as I was replying to your post. Twilight Zone music plays in the background.

Same thing happened as I was composing the post featuring the modded oil pump sprocket. Notice I directed it to Karack as he had mentioned something about doing a 1:1 sprocket on his 4 rotor. I had no idea he had slipped a post in some 14 minutes before I was done typing up my post. Now when you read through the thread, it looks like I typed that post up really fast or ninja edited it. ;)

It also meant I didn't need to type a PM to Karack informing of this new thread. Same with John Huijben. As I went to send him a PM, he was already here. :)

Hey Directfreak, thanks for your help back when I was looking for turbo stuff. Glad I decided to go NA on the 20B instead! I bet it'll be almost as nice as the 4 rotor.

Oh and before I forget, I'd like to send a strong thank you to Dan Atkins who let me paw through his rotors until I came up with some good candidates for lightening. Heavier than what I needed, but not too heavy. 4310 was the heaviest I attempted to lighten, followed by a 4292. Both turned out perfectly. I also got two sets of viton o-rings and apex seals. Now I'm just waiting on a set of apex springs..

I've got a mini update. I dry stacked the 4 rotor to test fit the Jeff Bruce long dowel pins. They fit nicely. Next I get to drill some flat steel to lock the housings and plates together so the engine can be stacked and rotated before the tension bolts are installed. Only necessary when using checkball oil squirters. Or if you're one of those hard core types who use the full flow squirters in a p-port, you can install them ahead of time and then stack from either direction.

*throws-head-back* AWWWWWWWWW-YEEEEAAAAAHHHHH!!!! I've always wanted to see a '24A'!!!!!!!

The mutually accepted name for a 4 rotor 12A is actually 23A because a 12A works out to under 600cc per rotor. Heck the 13B is only 654 per rotor. I'm embarassed that I can't recall what a 12A actually is in cc. But I do know the 3 rotor 12A is a 17A. The 2 rotor 12A is like 1130-40 something. It's early still... yawn.

1146cc! x2= 2292cc...

Thank you!

Now I've got a question about my multi hole stat bearings. Only the outer bearings are multi hole. The two in the intermediate plates are normal.

I think it should be ok because here is what Jeff Bruce says about his oil mods. It's #8.
"this mod is not a necessity only an upgrade for the oiling system."

Works for me. Sounds like multi hole outers and normal inners is a great choice. What do you guys think?

I have a question as well. With the new overdrive oil pump sprocket, we figured that at 7000 RPM on the 4-rotor, the oil pump will be spinning at the same speed as it would be at about 9500 RPM on a 12A. Do you think this will cause excessive wear on the oil pump? Will we run into cavitation issues?

Either way, we'll try it as is, monitoring oil pressure closely, but I think it would be a good idea to pull it off and inspect it after a while.