Awesome '74 engine (13B)
06-06-07, 05:26 PM
#26
Eats, Sleeps, Dreams Rotary
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Hey Jeff I just finished mine up. Heres the 83 intermediats w/ the 74 rotors, front and rear irons and 85 gsl-se housings. I guess from the outside there isnt that much of a difference. Frankenstein 4port 13b.lol
06-06-07, 05:32 PM
#27
what a ******* coincidence. I picked up the motor for my 73 RX-3 last Saturday. Almost the same **** but it has GSL-Se internals and old 13-B side plates. Didnt like the color so I stripped it down and painted it black plates and ford blue housings like the one in my 84 FB. Now I have 2 black eyes. . 
06-06-07, 06:33 PM
#31
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Hold up, I'm only a step or two behind you guys 
Scarey how great minds think alike. I just finished my teardown over the weekend, and while there was just a touch more chrome flaked off at the edge of the front housing than is maybe ideal, I'm going to go ahead because A) It's my first build and B) I'm broke!
One thing I've got is since I'm using a Weber 48, "primary/secondary" means very little, so I sourced out a center plate with ports very close to the front and rears... no sense in closing off the flow on one side when it just comes in the other was my thinking...
Picked up a little porting kit designed for small engines from Summit, should be perfect for cleaning up the corners of the housings. I'm just operating at about 1/3 speed compared to you guys!
Scarey how great minds think alike. I just finished my teardown over the weekend, and while there was just a touch more chrome flaked off at the edge of the front housing than is maybe ideal, I'm going to go ahead because A) It's my first build and B) I'm broke!
One thing I've got is since I'm using a Weber 48, "primary/secondary" means very little, so I sourced out a center plate with ports very close to the front and rears... no sense in closing off the flow on one side when it just comes in the other was my thinking...
Picked up a little porting kit designed for small engines from Summit, should be perfect for cleaning up the corners of the housings. I'm just operating at about 1/3 speed compared to you guys!
06-06-07, 08:44 PM
#32
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Jeff ,maybe I missed it, but why didnt you just use a 1st gen water pump? Will it not fit? Also the little pipe sticking out just below the oil cooler pedestal. whats it for or do we just cap that off.
gearhead-42, post some pics!
gearhead-42, post some pics!
06-06-07, 09:36 PM
#33
my newly painted motor. We will see what happens. If its below my standards, this stretport will be apart in no time. Comes with my favorite carb (48IDA of course), lightened flywheel and FB tranny with miata internals. the extra 12-A is my son's spare motor.
06-06-07, 10:01 PM
#34
I love all these pictures of 4 port 13Bs. 
Latin270, I could use a 1st gen waterpump, but all mine are old and leaking. The one previously on this engine went onto a friend's 4 port 13B because his bearing was bad. As luck would have it, I had that T2 housing laying around. All it needed was grinding on the back side to fit. I also had an FC impeller part which was going onto a different project, but it;s ok to use on this one. Also if and when I do a supecharger, they require you to use a 2nd gen waterpump becaue the idler pulley uses the three threaded holes on the front of the waterpump. Also the waterpump pullies only come in the FC 8 bolt pattern. That's fine because I also have one FC fan laying around.
What's even cooler is an aluminum GMB aftermarket 1st gen waterpump impeller I'd kept from the very first engine I tore down in '01, feels like the seal is still good in it. It was burried in a box out of site for the last several years. I haven't dug the cast iron housing out yet. Then it dawned on me. I have one more T2 housing laying around. Why couldn't I install the aluminum impeller on the aluminum housing? Serious weight savings!
Wait a minute there. Whoa Nelly! Forget about using a clutch fan with this. Mazda used cast iron because it's strong and can handle the weight of the clutch fan. I doubt having both parts in aluminum would last long without leaks. That's ok because the next project will use an electric fan, and any weight savings, especially at the extreme end of the engine, is a plus.
Oh, you were asking about the heater core fitting? On one 13B 4 port I installed in my MG Midget, I swapped it for a short bolt (plug) from Racing Beat since that car's heater core was ditched long ago. As for my '74 engine, I'm keeping it as is. No reason to change it for a longer one or block it off.
Latin270, I could use a 1st gen waterpump, but all mine are old and leaking. The one previously on this engine went onto a friend's 4 port 13B because his bearing was bad. As luck would have it, I had that T2 housing laying around. All it needed was grinding on the back side to fit. I also had an FC impeller part which was going onto a different project, but it;s ok to use on this one. Also if and when I do a supecharger, they require you to use a 2nd gen waterpump becaue the idler pulley uses the three threaded holes on the front of the waterpump. Also the waterpump pullies only come in the FC 8 bolt pattern. That's fine because I also have one FC fan laying around.
What's even cooler is an aluminum GMB aftermarket 1st gen waterpump impeller I'd kept from the very first engine I tore down in '01, feels like the seal is still good in it. It was burried in a box out of site for the last several years. I haven't dug the cast iron housing out yet. Then it dawned on me. I have one more T2 housing laying around. Why couldn't I install the aluminum impeller on the aluminum housing? Serious weight savings!
Wait a minute there. Whoa Nelly! Forget about using a clutch fan with this. Mazda used cast iron because it's strong and can handle the weight of the clutch fan. I doubt having both parts in aluminum would last long without leaks. That's ok because the next project will use an electric fan, and any weight savings, especially at the extreme end of the engine, is a plus.
Oh, you were asking about the heater core fitting? On one 13B 4 port I installed in my MG Midget, I swapped it for a short bolt (plug) from Racing Beat since that car's heater core was ditched long ago. As for my '74 engine, I'm keeping it as is. No reason to change it for a longer one or block it off.
06-06-07, 11:53 PM
#35
u can add me to that list too. the intermediates and rotor housings r from '74, and the w/p, pump housing, and e-shaft from an '86 or '87. i was going for the cast, aluminum, cast, aluminum effect. the early fc pump housing allowed me to keep the '74 2 bolt top hose connection above the T-stat.
Last edited by rxtasy3; 06-07-07 at 12:06 AM.
06-07-07, 11:03 AM
#37
This 13B 4 port went into my MG Midget. It has Y side plates ported to '74 spec and '74 rotor housings. The rotating assembly is kind of a mismatch from '74-'78 but both rotors are C. Light steel flywheel and 215mm disc and pressure plate.
06-07-07, 11:08 AM
#38
Here is the RX-4 wagon with its first engine, which had '74 rotor housings.
http://i60.photobucket.com/albums/h1...6/DSCN9948.jpg
And the second engine with GSL-SE rotor housings and rotating assembly.
http://i60.photobucket.com/albums/h1...6/DSCN9948.jpg
And the second engine with GSL-SE rotor housings and rotating assembly.
06-07-07, 12:29 PM
#39
Well, you better add me too.
This is a Tall Port R5, with S5 rotating assembly. Plates lapped and re-nitrided. Street ported, oil moded, etc.
On another note: one comment of Jeff's that I must take exeption to is that softer apex seals are by their nature friendlier to rotor housings. I do not agree. Abrasive materials are often very soft...grinding wheels, for example. With the exception of self-lubricating carbon-aluminum, softer apex seals are almost always significantly more abrasive than the factory steel seals. This is true of all the aftermarket metallic seals we have ever tested. For example, Hurley seals, which are about the softest out there, are the MOST abrasive in our experience. Other brands are not much better. Just FYI.
This is a Tall Port R5, with S5 rotating assembly. Plates lapped and re-nitrided. Street ported, oil moded, etc.
On another note: one comment of Jeff's that I must take exeption to is that softer apex seals are by their nature friendlier to rotor housings. I do not agree. Abrasive materials are often very soft...grinding wheels, for example. With the exception of self-lubricating carbon-aluminum, softer apex seals are almost always significantly more abrasive than the factory steel seals. This is true of all the aftermarket metallic seals we have ever tested. For example, Hurley seals, which are about the softest out there, are the MOST abrasive in our experience. Other brands are not much better. Just FYI.
06-07-07, 04:55 PM
#41
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Who else?
1. Jeff20b
2. WackyRacer
3. Latin270
4. Midwest 7's
5. rxtasy3
6. Blake
7. Gearhead-42
So obviously mine is is a few more pieces than most, but it's progressing...
Early FC water pump, -SE alternator, multi rib pulley kit, Weber 48 IDA, and they're "B" rotors...
The housings are ported for torque... I'll be widening slightly but not changing timing much.
My old center plate (right) vs the new one (Thanks RX3SP!)... both R5 castings btw...
And finally the new center compared to my rear plate; REALLLLLY close...
If you refer to this thread you can see some of the motors' history...
1. Jeff20b
2. WackyRacer
3. Latin270
4. Midwest 7's
5. rxtasy3
6. Blake
7. Gearhead-42
So obviously mine is is a few more pieces than most, but it's progressing...
Early FC water pump, -SE alternator, multi rib pulley kit, Weber 48 IDA, and they're "B" rotors...
The housings are ported for torque... I'll be widening slightly but not changing timing much.
My old center plate (right) vs the new one (Thanks RX3SP!)... both R5 castings btw...
And finally the new center compared to my rear plate; REALLLLLY close...
If you refer to this thread you can see some of the motors' history...
06-08-07, 01:24 AM
#43
Interesting info, Blake. Nice looking engine too. It makes sense that the harder they are, the less abrasive they are. In comparing the oil seals from a nitrided engine to a non nitrided engine, the ones from the nitrided engines are always worn less. The hard nitrided surface is less abrasive.
My next 13B 4 port will get dark red side plates and silver aluminum housings. I think they'll match the project car pretty well.
Gearhead-42, you might want to reconsider going any wider on your exhaust ports. Keep them at their current width and height. In other words, at their current "cross section". Scroll down near the bottom where it says Low RPM Operation. http://www.yawpower.com/febtech.html
I especially love this paragraph:
1. Later exhaust port opening. Since we have more time to exhaust the chamber, the total exhaust duration can be lessend. The result of this will be that we can hold pressure in the chamber for a greater period of time. This will increase the amount of time that torque will be applied to the eccentric shaft.
Also pay attention to 2. Smaller cross sectional areas.
I have a set of identical housings to yours, since they came from the exact same engines, and I'm keeping my exhaust ports entirely stock. The only change I'm making to change actual flow numbers is the swapping in of a Y intermediate plate and the intake manifold. Of course all the other changes like a high volume oil pump etc will be made as well.
The original front and rear plates went into an engine for a friend already, along with a set of more appropriate rotor housings for his application (REPU). That's fine though because they're not nitrided and I swapped in a Y intermediate plate and ported them all to '74 spec. A similar engine I did for his truck (nitrided R5 ported to '74 spec) turned out exceptionally well.
I had to come up with a complete set of side plates and another rotating assembly for these special rotor housings, and I ended up with two C rotors from a water damaged nitrided R5. The rotating assembly was fine, but only one rotor housing and the rear plate were useable. The rotor housing went into my white REPU and the rear plate is sitting on my shelf.
My next 13B 4 port will get dark red side plates and silver aluminum housings. I think they'll match the project car pretty well.
Gearhead-42, you might want to reconsider going any wider on your exhaust ports. Keep them at their current width and height. In other words, at their current "cross section". Scroll down near the bottom where it says Low RPM Operation. http://www.yawpower.com/febtech.html
I especially love this paragraph:
1. Later exhaust port opening. Since we have more time to exhaust the chamber, the total exhaust duration can be lessend. The result of this will be that we can hold pressure in the chamber for a greater period of time. This will increase the amount of time that torque will be applied to the eccentric shaft.
Also pay attention to 2. Smaller cross sectional areas.
I have a set of identical housings to yours, since they came from the exact same engines,
and I'm keeping my exhaust ports entirely stock. The only change I'm making to change actual flow numbers is the swapping in of a Y intermediate plate and the intake manifold. Of course all the other changes like a high volume oil pump etc will be made as well. The original front and rear plates went into an engine for a friend already, along with a set of more appropriate rotor housings for his application (REPU). That's fine though because they're not nitrided and I swapped in a Y intermediate plate and ported them all to '74 spec. A similar engine I did for his truck (nitrided R5 ported to '74 spec) turned out exceptionally well.
I had to come up with a complete set of side plates and another rotating assembly for these special rotor housings, and I ended up with two C rotors from a water damaged nitrided R5. The rotating assembly was fine, but only one rotor housing and the rear plate were useable. The rotor housing went into my white REPU and the rear plate is sitting on my shelf.
06-08-07, 01:44 AM
#44
Gearhead-42, would you be interested in starting a new thread detailing the build of your engine? I will start a new one detailing the build of mine. Since both will be based on those rotor housings with the interesting port location, maybe we could both post in it as joint contributors or something?
Don't worry about how long it will take to build yours or whatever. I'm not under any time constaints with this next engine. I was with the '74 engine. I've only posted pictures when it's convenient. I'd like this next engine expose to be thorough and I know lots of people are interested. Even another forum full of people are interested. I told them I'd detail the project if enough people were interested. Since then I've realised that if you post it, they will come. Same here I suppose. Gotta keep it interesting, of course. Interested?
Don't worry about how long it will take to build yours or whatever. I'm not under any time constaints with this next engine. I was with the '74 engine. I've only posted pictures when it's convenient. I'd like this next engine expose to be thorough and I know lots of people are interested. Even another forum full of people are interested. I told them I'd detail the project if enough people were interested. Since then I've realised that if you post it, they will come. Same here I suppose. Gotta keep it interesting, of course. Interested?
06-08-07, 05:28 AM
#45
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Gearhead-42, would you be interested in starting a new thread detailing the build of your engine? I will start a new one detailing the build of mine. Since both will be based on those rotor housings with the interesting port location, maybe we could both post in it as joint contributors or something?
That could be really interesting for folks... see how two people with the same basic starting point approach rebuilding for their own purposes...
I'm game!
Dan
Oh, and I read that article you linked... great stuff! I keep thinking in cam analogues... High lift, short duration intake (big ports, but not very long) and a short duration, low(er) lift exhaust, a bit retarded. Sounds like a towing package!
06-08-07, 10:24 AM
#46
Heh, you gotta start somewhere. I never had to deal with cams before so I'm basically rotary-only terminology at this point. Not a bad starting point.
Would you like to start a thread or should I? I think we should both contribute to it. I already have a thread about the project car itself. It'd be great to link the engine build thread to it.
Yeah, let's start a thread called a tale of two motors. Should I do the honors? Yeah, why not? Ok I'll start it... and here's a link. https://www.rx7club.com/forum/showth...32#post7022832
Would you like to start a thread or should I? I think we should both contribute to it. I already have a thread about the project car itself. It'd be great to link the engine build thread to it.
Yeah, let's start a thread called a tale of two motors.
Should I do the honors? Yeah, why not? Ok I'll start it... and here's a link. https://www.rx7club.com/forum/showth...32#post7022832
06-09-07, 11:17 AM
#47
Lookee what I picked up yesterday.
Edelbrock 600. I think I'll try it on this engine after 500 miles of break in time. Nah, let's make it an even 600 miles lol.
Got done painting the water pump parts. Just gotta test fit the pullies to make sure the sheaves line up.
The tranny crossmember thing after slotting the holes to fit a 5 speed. Next I need to slot the holes on the rubber tranny mount and grind a little notch to fit the tranny in its new position.
Edelbrock 600. I think I'll try it on this engine after 500 miles of break in time. Nah, let's make it an even 600 miles lol.
Got done painting the water pump parts. Just gotta test fit the pullies to make sure the sheaves line up.
The tranny crossmember thing after slotting the holes to fit a 5 speed. Next I need to slot the holes on the rubber tranny mount and grind a little notch to fit the tranny in its new position.
06-09-07, 04:25 PM
#48
Eats, Sleeps, Dreams Rotary
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Yes! I think you enjoy the Edelbrock. I have the 500cfm on my 12a. I hope it will work well the the 13b but I wont know until I put it on and fire her up. Looking good Jeff!
06-10-07, 01:36 AM
#49
Did you start a thread detailing the build of your 13B? I remember the initial thread when you first got it. We determined it was a '74-'75 engine (kinda like mine!). Is the build detailed in that thread as well? Did you even start on it yet?
Yeah it'll be interesting to test this Edelbrock out on the 13B with only '74 spec ports. Since they were smoothed and shaped better than factory ports, the flow numbers ought to be noticebly higher. Perhaps high enough for the 600.
Stock '74 exhaust ports a really small so I chose the ported set for this engine since I knew the lower geared rearend would make up for some of the loss of low end which might result. Also I planned to supercharge anyway so it made sense. The other engine which got the stock ported set went into the MG, and they had a little missing chrome, so no big loss. The side plates were a little less than perfect; one looking like it survived the death of an apex seal, what with little scratches here and there, and varying levels of step wear on all four surfaces. All used seals too. They'll be just fine to get the MG running as cheaply as possible, and the power loss is no big thing. The old REPU engine was gutless in the REPU but disturbingly powerful in the MG, just to give you an idea of what I'm working with here. Now with the correct intermediate plate for the Cosmo manifold, when those secondaries open, hold me. And I thought it was scary on just primaries. Same apex seals, one rotor and housing from the old REPU engine, so one side of the engine is technically already sort of broken in. It should have pretty good power on its first test drive.
I got a little done on the REPU engine. Having decided what I want to do with the other waterpump, and no longer needing access to the gasket and the iron impeller, I gooped them up with RTV and installed them along with the bolt for the alt braket. To get the angle of the bracket right, I installed an alternator so I could torque the bolt down with the rest of the bolts and nuts. It's a 16mm bolt. Weird. That's ok because I found a 15mm nut for the other waterpump bracket. Might as well grab a couple of 18mm and 13mm bolts and have VW and Fiat party while I'm at it.
Yeah it'll be interesting to test this Edelbrock out on the 13B with only '74 spec ports. Since they were smoothed and shaped better than factory ports, the flow numbers ought to be noticebly higher. Perhaps high enough for the 600.
Stock '74 exhaust ports a really small so I chose the ported set for this engine since I knew the lower geared rearend would make up for some of the loss of low end which might result. Also I planned to supercharge anyway so it made sense. The other engine which got the stock ported set went into the MG, and they had a little missing chrome, so no big loss. The side plates were a little less than perfect; one looking like it survived the death of an apex seal, what with little scratches here and there, and varying levels of step wear on all four surfaces. All used seals too. They'll be just fine to get the MG running as cheaply as possible, and the power loss is no big thing. The old REPU engine was gutless in the REPU but disturbingly powerful in the MG, just to give you an idea of what I'm working with here.
Now with the correct intermediate plate for the Cosmo manifold, when those secondaries open, hold me. And I thought it was scary on just primaries. Same apex seals, one rotor and housing from the old REPU engine, so one side of the engine is technically already sort of broken in. It should have pretty good power on its first test drive.I got a little done on the REPU engine. Having decided what I want to do with the other waterpump, and no longer needing access to the gasket and the iron impeller, I gooped them up with RTV and installed them along with the bolt for the alt braket. To get the angle of the bracket right, I installed an alternator so I could torque the bolt down with the rest of the bolts and nuts. It's a 16mm bolt. Weird. That's ok because I found a 15mm nut for the other waterpump bracket. Might as well grab a couple of 18mm and 13mm bolts and have VW and Fiat party while I'm at it.
06-10-07, 12:52 PM
#50
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Actually I didnt take pics and a detailed write up like I wanted when I broke down the engine because my hands where full of oil and my wife didnt want the camera all greasy. lol So my plan was to break the 74' down a bit at a time, take pics then go to the next step.
However as I took apart the old 74 13b w/ "low miles" I was a bit disapointed to find 1 housing in bad shape (flaking), the other is mint. I decided to then go the next step and just saw what was usable and what wasnt. After deciding to use the gsl-se housing and porting it out I felt the street ported 83 intermediate would be the best choice considering the size of the secondaries on the 74 plates.
So after painting then carefully putting her back together w/ new soft seals I took the above pics and the rest is my own little rotary history. I still need to put the oil pan and water pump on before I drop her in 2 weeks from now. My future motor will be based on the results of this one. I'm not a big fan of flowbench testing and all the science behind it. I'm simply a backyard mechanic and use the old trial and error method.
However as I took apart the old 74 13b w/ "low miles" I was a bit disapointed to find 1 housing in bad shape (flaking), the other is mint. I decided to then go the next step and just saw what was usable and what wasnt. After deciding to use the gsl-se housing and porting it out I felt the street ported 83 intermediate would be the best choice considering the size of the secondaries on the 74 plates.
So after painting then carefully putting her back together w/ new soft seals I took the above pics and the rest is my own little rotary history. I still need to put the oil pan and water pump on before I drop her in 2 weeks from now. My future motor will be based on the results of this one. I'm not a big fan of flowbench testing and all the science behind it. I'm simply a backyard mechanic and use the old trial and error method.
Last edited by Latin270; 06-10-07 at 12:59 PM.