89-91 13B BP swap, have ?'s...
08-29-02, 12:11 PM
#1
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89-91 13B BP swap, have ?'s...
My friend just bought an 85 GSL a couple days ago. I don't know much about 1st Gens. I've searched around for some info and have gathered this...
The 13B will need to have the 12A front plate on it. So, could we just use all the 12A side housings and use the 13B rotor housings? With the 89-91 NA rotors, we'd use the counterweights from the same motor along w/ the e-shaft, correct?
It's going to be a BP'd motor (not into the water jacket) and run carbs. Which intake/s will fit those housings? I'm just guessing that if we used the 12A housings, an 85 12A intake will work, but we'd need to use a 13B compatible header...
What would be the better tranny to use also? I've looked into the swaps, some say put in a T2 tranny, GSL-SE tranny, keep the 12A one... which is better? The T2 tranny has to high of a 5th gear, what other options are there? I've heard something of swapping in Miata gears into a RX7 (year? model?) case.
The 13B will need to have the 12A front plate on it. So, could we just use all the 12A side housings and use the 13B rotor housings? With the 89-91 NA rotors, we'd use the counterweights from the same motor along w/ the e-shaft, correct?
It's going to be a BP'd motor (not into the water jacket) and run carbs. Which intake/s will fit those housings? I'm just guessing that if we used the 12A housings, an 85 12A intake will work, but we'd need to use a 13B compatible header...
What would be the better tranny to use also? I've looked into the swaps, some say put in a T2 tranny, GSL-SE tranny, keep the 12A one... which is better? The T2 tranny has to high of a 5th gear, what other options are there? I've heard something of swapping in Miata gears into a RX7 (year? model?) case.
08-29-02, 12:32 PM
#2
Old [Sch|F]ool
You can't mix '86-up housings with '85-down housings. You'd need to use GSL-SE rotor housings.
Whether or not you can use later rotors in an early engine, I can't say. Some people do it, other people say they tried and had interference.
For intake, you can use anything designed for a "4 port 13B", or specifically a "74-78 13B". The '74-78 13Bs used the same side housings as '74-78 12As, which are interchangeable up to '85.
GSL-SE is the same tranny as a 12A trans. I'd use the T2 tranny. Yes 5th gear is tall but so what? Who uses 5th gear?
You COULD do a Miata gear swap but it won't be any stronger than a GSL-SE/12A trans.
Whether or not you can use later rotors in an early engine, I can't say. Some people do it, other people say they tried and had interference.
For intake, you can use anything designed for a "4 port 13B", or specifically a "74-78 13B". The '74-78 13Bs used the same side housings as '74-78 12As, which are interchangeable up to '85.
GSL-SE is the same tranny as a 12A trans. I'd use the T2 tranny. Yes 5th gear is tall but so what? Who uses 5th gear?
You COULD do a Miata gear swap but it won't be any stronger than a GSL-SE/12A trans.
08-29-02, 12:50 PM
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Ok, just so I'm tracking on your info...
I'd have to get GSL-SE rotor housings to use with the 12A side housings.
Any 74-78 4-port 13B intake will work.
T2 Tranny is the best option.
I'd have to get GSL-SE rotor housings to use with the 12A side housings.
Any 74-78 4-port 13B intake will work.
T2 Tranny is the best option.
08-29-02, 12:56 PM
#4
Old [Sch|F]ool
Right.
Now you *could* use a N/A trans... it'll bolt up and it'll "work" but it won't take as much abuse.
whichever tranny you use, you just need to have the correct flywheel and clutch. I'll assume that you're going to be going with a lightweight flywheel... you get the rear counterweight that matches the rotors you are using and then get a lightweight flywheel that matches your trans (N/A flywheel for N/A trans, Turbo flywheel for Turbo trans)
Now you *could* use a N/A trans... it'll bolt up and it'll "work" but it won't take as much abuse.
whichever tranny you use, you just need to have the correct flywheel and clutch. I'll assume that you're going to be going with a lightweight flywheel... you get the rear counterweight that matches the rotors you are using and then get a lightweight flywheel that matches your trans (N/A flywheel for N/A trans, Turbo flywheel for Turbo trans)
08-29-02, 12:59 PM
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I couldn't find any argument really for or against a lightened flywheel. I know it reduces rotational mass, but it also makes the car loose "oomph" (for lack of a better word) on take off. It'll be street car, but my idea of streetable is pretty loose.
Does the NA and the T2 tranny both have the same gearing, or are they different and which would be better?
I'm putting together a "shopping list" of parts right now... thanks for the feedback.
Does the NA and the T2 tranny both have the same gearing, or are they different and which would be better?
I'm putting together a "shopping list" of parts right now... thanks for the feedback.
08-29-02, 01:27 PM
#6
Originally posted by FastX7
Does the NA and the T2 tranny both have the same gearing, or are they different and which would be better?
Does the NA and the T2 tranny both have the same gearing, or are they different and which would be better?
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08-29-02, 01:57 PM
#8
You can find intake manifolds for 13b 4 ports all over, most commonly for a 2bbl downdraft like the weber ida/idf. europeanmotorworks.com had a few in their display counter a few weeks ago. You can also find adaptor plates to adapt 12a manifold to 13b but i'd rather not use those. more $, work, and bolts to strip out.
Did Racing Beat make a 13b 4port holley setup?
You can use the later lighter weight 89-91 N/A rotors, and e-shaft and counterweights. You need the whole rotating assembly in order to keep it in balance. Speaking of, if you're gonna rev it over 8500rpms you really should have it rebalanced too. And clearanced. And $350 carbon apex seals/springs. And... (I just bought a 12a bridgeport for the racecar).
Any 1st gen trans can handle a street driven and tired 13b bridge. My friend has a 13b PP on his Rx3 road race car and he uses a 1st gen 12a trans, 3rd member and diff! And he has wide sticky tires. Remember, lots of power and wide sticky tires = snapped drivetrain. Lots of power and wheelspin = less friction and resistance and much less to no snappage. Slower due to less traction, but cheaper due to less drivetrain replacement and cheaper smaller tires. etc.. etc...
You should only use a Turbo ][ trans in a turbo application where you have lots of torque. My buddy's 12a bridgeport GT3 racecar had a 79--82 626 trans in it for 2.5 years no prob. Better gear ratios too! Dat's what I got now.
I used a 17lb RB light steel flywheel on my 12a streetport for years and it was bitchin! Lots of revvs, just had to slip the clutch a *tad more*. No big deal. I wouldhave gone to aluminum if I could do it over again.
Hope this helps@!
-bp-
Did Racing Beat make a 13b 4port holley setup?
You can use the later lighter weight 89-91 N/A rotors, and e-shaft and counterweights. You need the whole rotating assembly in order to keep it in balance. Speaking of, if you're gonna rev it over 8500rpms you really should have it rebalanced too. And clearanced. And $350 carbon apex seals/springs. And... (I just bought a 12a bridgeport for the racecar).
Any 1st gen trans can handle a street driven and tired 13b bridge. My friend has a 13b PP on his Rx3 road race car and he uses a 1st gen 12a trans, 3rd member and diff! And he has wide sticky tires. Remember, lots of power and wide sticky tires = snapped drivetrain. Lots of power and wheelspin = less friction and resistance and much less to no snappage. Slower due to less traction, but cheaper due to less drivetrain replacement and cheaper smaller tires. etc.. etc...
You should only use a Turbo ][ trans in a turbo application where you have lots of torque. My buddy's 12a bridgeport GT3 racecar had a 79--82 626 trans in it for 2.5 years no prob. Better gear ratios too! Dat's what I got now.
I used a 17lb RB light steel flywheel on my 12a streetport for years and it was bitchin! Lots of revvs, just had to slip the clutch a *tad more*. No big deal. I wouldhave gone to aluminum if I could do it over again.
Hope this helps@!
-bp-
08-29-02, 02:04 PM
#9
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-bp-
That was some really informative reading. How did your buddy get a 626 tranny onto the 12A? That'd be something that I would consider. I was just looking at the gearing listing that DIRECTFREAK posted and if I had to use anything (from a 7) it'd be the 79-83 12A tranny, had the best ratios available. I'm also considering putting in a 4.444 rear-end (85?) or a 4.3 if possible.
That was some really informative reading. How did your buddy get a 626 tranny onto the 12A? That'd be something that I would consider. I was just looking at the gearing listing that DIRECTFREAK posted and if I had to use anything (from a 7) it'd be the 79-83 12A tranny, had the best ratios available. I'm also considering putting in a 4.444 rear-end (85?) or a 4.3 if possible.
08-29-02, 02:48 PM
#10
Old [Sch|F]ool
Go for the lightweight flywheel! If you feel like you "loose oomph" then you need to learn to drive using the throttle and engine power instead of letting the engine's inertia do the work.
The point of going for more power is quicker acceleration, yes? So you should concentrate on making the rotating assembly lighter so the engine can accelerate itself easier so more power is used to accelerate the car instead of the engine. (And now you know why I get high on '83-up 12A's...
)
The 626 trans has the closest ratios. Next-best is the Miata trans. The internals are the "same" as N/A RX-7 internals. I'd prefer to use pre-'83 gearing if using an all RX-7 trans because the teeth are coarser (stronger).
If you're interested in drag racing you may not like the non-RX-7 transmissions. 1st gear is a lot taller in the Miata/626 trannies. A long time ago I calculated that you'd need 4.444 (or was it 4.778?) gears just to have the same 1st gear as an RX-7 trans with 3.909! Of course then you wouldn't have that awful 2-3 shift RPM drop like with the RX-7 trans...
The point of going for more power is quicker acceleration, yes? So you should concentrate on making the rotating assembly lighter so the engine can accelerate itself easier so more power is used to accelerate the car instead of the engine. (And now you know why I get high on '83-up 12A's...
)The 626 trans has the closest ratios. Next-best is the Miata trans. The internals are the "same" as N/A RX-7 internals. I'd prefer to use pre-'83 gearing if using an all RX-7 trans because the teeth are coarser (stronger).
If you're interested in drag racing you may not like the non-RX-7 transmissions. 1st gear is a lot taller in the Miata/626 trannies. A long time ago I calculated that you'd need 4.444 (or was it 4.778?) gears just to have the same 1st gear as an RX-7 trans with 3.909! Of course then you wouldn't have that awful 2-3 shift RPM drop like with the RX-7 trans...
Last edited by peejay; 08-29-02 at 02:51 PM.
08-29-02, 02:57 PM
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I was looking at the pre-83 trans, and that's what I'm going to shoot for. So, you think an aluminum flywheel would be best for drag racing? Just have to slip out the clutch a little more and get used to it. I was just saying what I've heard or know about lightweight flywheels, I've never drove/owned one. With the flywheel, if I have an 89-91 rotating assembly, will I need a flywheel and clutch for a 89-91 car?
08-29-02, 03:06 PM
#12
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If you're using the lightweight flywheel, you'd probably want to get some deeper gearing and/or a "loose" clutch, to make launching a lot less tricky.
08-29-02, 03:14 PM
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89-91 9.7:1 CR Rotors
89-91 E-Shaft
84-85 GSL-SE Rotor Housings
84-85 12A Side Housings
87-91 T2 Tranny (and starter)
87-91 Flywheel and Clutch
84-85 13B Intake System
79-85 13B Exhaust System
4.3 gearing (is that possible w/ the GSL rear-end?)
Assuming I'll need a custom driveshaft
Haven't decided on DLIDFIS or MSD DFIS...
That's what I have so far, am I missing anything or is anything incorrect?
89-91 E-Shaft
84-85 GSL-SE Rotor Housings
84-85 12A Side Housings
87-91 T2 Tranny (and starter)
87-91 Flywheel and Clutch
84-85 13B Intake System
79-85 13B Exhaust System
4.3 gearing (is that possible w/ the GSL rear-end?)
Assuming I'll need a custom driveshaft
Haven't decided on DLIDFIS or MSD DFIS...
That's what I have so far, am I missing anything or is anything incorrect?
08-29-02, 03:21 PM
#14
Old [Sch|F]ool
I don't think they make a 4.3 for the rear in the GSL.
Some Miatas (and a few rare pickup trucks...) had 4.444:1 gears. Kia Sportages in the US have 4.778 gears and the front gears are the same as ours. (NZ SPortages had something like 4.675 or something but again it's the standard "short nose" Mazda 7" diff that 1st-gens have)
Get confirmation that '89-91 rotors will work in a pre-85 rotor housing. If you can use them, you will need '89-up counterweights.
The E-shaft... you can use any '92-earlier 13B E-shaft. If you use an '85-earlier one you don't have to worry about the thermal pellet dealy. Because they're so expensive, it's probably best to just use whatever you get.
As for ignition... why even bother deciding? You've already got a big cash outlay detailed, might as well spend the $350 and get a pair of MSD 6ALs. No point in scrimping a little money when you're already spending several thousand!
Some Miatas (and a few rare pickup trucks...) had 4.444:1 gears. Kia Sportages in the US have 4.778 gears and the front gears are the same as ours. (NZ SPortages had something like 4.675 or something but again it's the standard "short nose" Mazda 7" diff that 1st-gens have)
Get confirmation that '89-91 rotors will work in a pre-85 rotor housing. If you can use them, you will need '89-up counterweights.
The E-shaft... you can use any '92-earlier 13B E-shaft. If you use an '85-earlier one you don't have to worry about the thermal pellet dealy. Because they're so expensive, it's probably best to just use whatever you get.
As for ignition... why even bother deciding? You've already got a big cash outlay detailed, might as well spend the $350 and get a pair of MSD 6ALs. No point in scrimping a little money when you're already spending several thousand!
08-29-02, 03:32 PM
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Great thread...
You need to get the rear counterweight for the 89-91 rotating assembly and a flywheel and clutch to suit your gearbox choice... ie. n/a or T2.
Originally posted by FastX7
With the flywheel, if I have an 89-91 rotating assembly, will I need a flywheel and clutch for a 89-91 car?
With the flywheel, if I have an 89-91 rotating assembly, will I need a flywheel and clutch for a 89-91 car?
08-29-02, 03:57 PM
#16
626 instructions are on the bottom. I have one of these trans too and the gearing is real nice. The gears are physically approx 1mm thinner than 1st gens so be careful, but they can take a full road race slicked 12a bp for 2.5+ years!
https://www.rx7club.com/forum/showth...&highlight=626
4.444 is a good set of gears. 87-88 mazda pickup 4wd front diff has that r&p if you can find one in the boneyard to pluck. 4.3 and other 2nd gen r&p's have a long pinion that won't work with 1st gen. suzuki sportage front diff has 5.12!
Use a sprung center clutch disk on the street, especially with the 626 box (less shockloading on that delicate trans).
89-91 rotors will work with pre 85 rotor housings. Been there, seen that. Much cheaper rotor housings, but not the 'latest design'.
I think blake posted a thread on the forum on putting a T][ trans into 1st gen. Required custom aluminum spacers and driveshaft.
You;ll need to mess with the gsl-se 6-port intake manifold to fit a 12a 4 port.
-bp-
https://www.rx7club.com/forum/showth...&highlight=626
4.444 is a good set of gears. 87-88 mazda pickup 4wd front diff has that r&p if you can find one in the boneyard to pluck. 4.3 and other 2nd gen r&p's have a long pinion that won't work with 1st gen. suzuki sportage front diff has 5.12!
Use a sprung center clutch disk on the street, especially with the 626 box (less shockloading on that delicate trans).
89-91 rotors will work with pre 85 rotor housings. Been there, seen that. Much cheaper rotor housings, but not the 'latest design'.
I think blake posted a thread on the forum on putting a T][ trans into 1st gen. Required custom aluminum spacers and driveshaft.
You;ll need to mess with the gsl-se 6-port intake manifold to fit a 12a 4 port.
-bp-
08-29-02, 04:29 PM
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The budget is approx. $5000, at first. That's just to get the main stuff, it will be an ever-going project between us probably. I'd like to eventrually run it in the All-Motor class, put it up for rotaries.
Would a 5.12 in the rear-end be to much? I'll probably just end up trying them both out and seeing what happens.
I haven't done alot of research on the ignition... does the MSD 6AL have a two-step in it? I'm not sure how to wire that setup in, is it like the MSD DFIS?
I'll probably stick with the T2 tranny to have something a bit more beffier, I don't hvae the money for a dogbox now, but that's what it'll become down the road. I believe I read some or all of the read you're referring to about the spacers and driveshaft for a T2 tranny into a 1st Gen.
I'll probably just call Mazdatrix with my question for the intake when I'm ready to order it.
Thanks for all the help guys, this is a great informative thread. I've always toyed around with this idea... but now is my first chance to make it happen.
Would a 5.12 in the rear-end be to much? I'll probably just end up trying them both out and seeing what happens.
I haven't done alot of research on the ignition... does the MSD 6AL have a two-step in it? I'm not sure how to wire that setup in, is it like the MSD DFIS?
I'll probably stick with the T2 tranny to have something a bit more beffier, I don't hvae the money for a dogbox now, but that's what it'll become down the road. I believe I read some or all of the read you're referring to about the spacers and driveshaft for a T2 tranny into a 1st Gen.
I'll probably just call Mazdatrix with my question for the intake when I'm ready to order it.
Thanks for all the help guys, this is a great informative thread. I've always toyed around with this idea... but now is my first chance to make it happen.
08-29-02, 04:49 PM
#18
Old [Sch|F]ool
Originally posted by DriveFast7 and edited for clarity
87-88 mazda pickup 4wd front diff has that r&p if you can find one in the boneyard to pluck. 4.3 and other 2nd gen r&p's have a long pinion that won't work with 1st gen. suzuki sportage front diff has 5.12!
You;ll need to mess with the gsl-se 6-port intake manifold to fit a 12a 4 port.
87-88 mazda pickup 4wd front diff has that r&p if you can find one in the boneyard to pluck. 4.3 and other 2nd gen r&p's have a long pinion that won't work with 1st gen. suzuki sportage front diff has 5.12!
You;ll need to mess with the gsl-se 6-port intake manifold to fit a 12a 4 port.
The Kia Sportage (NOT Suzuki) has 4.778 in the US, 4.625 (not 4.675 as I thought before) in NZ. No production 5.12 gears.
Why bother messing with a GSL-SE intake? You can find IDA, DCOE, or Holley intakes for 13B 4-port no problem. Or you can use a factory one from a '74-78 13B if you're sick enough
08-29-02, 04:51 PM
#19
Old [Sch|F]ool
Originally posted by FastX7
Would a 5.12 in the rear-end be to much? I'll probably just end up trying them both out and seeing what happens.
I haven't done alot of research on the ignition... does the MSD 6AL have a two-step in it? I'm not sure how to wire that setup in, is it like the MSD DFIS?
Would a 5.12 in the rear-end be to much? I'll probably just end up trying them both out and seeing what happens.
I haven't done alot of research on the ignition... does the MSD 6AL have a two-step in it? I'm not sure how to wire that setup in, is it like the MSD DFIS?
The 6AL does not have a two-step, but it can be added. It's just wired in normally. Not sure what "MSD DFIS" is.
08-29-02, 05:37 PM
#21
Old [Sch|F]ool
Yes, you could. In fact you can now get via Mazdatrix a manifold to fit an IDA Weber to a Turbo ('86-92) 4-port engine.
http://www.mazdatrix.com/r-idamanifolds.htm
You can see the flange difference between 18105 (for "Turbo" style 4-ports) and 18103 (for "74-78" style 4-ports).
http://www.mazdatrix.com/r-idamanifolds.htm
You can see the flange difference between 18105 (for "Turbo" style 4-ports) and 18103 (for "74-78" style 4-ports).
08-29-02, 05:51 PM
#22
5.12 on the street would be a little too short.
Suzuki Samauri Grand Vitara has the 5.12, sorry! The teeth are thinner but I have never heard of a road racer snapping one. Has anyone else? Drag racing is another story and if you abuse your drivetrain like that you deserve to be under the car with a wrench.
Take a look at this webpage. The Suzuki Samuri Grand Vitara 4wd uses 4.875 and 5.12 gears. Probablly on the front axel like the Kia Sportage and the 87-88 Mazda B2000 trucks do. Since these are the same axel ratios as the MazdaComp sells, do you think, perchance, they are the same size ring and pinion as the first gen Rx-7? Might be an alternate source for such gears.
Page 17.
http://www.greenhouse.gov.au/fuelguide/fcg99_00.pdf
?5.83 anyone?
http://www.vintagesuzuki.com/main_ca...icktracker.htm
-bp-
Suzuki Samauri Grand Vitara has the 5.12, sorry! The teeth are thinner but I have never heard of a road racer snapping one. Has anyone else? Drag racing is another story and if you abuse your drivetrain like that you deserve to be under the car with a wrench.
Take a look at this webpage. The Suzuki Samuri Grand Vitara 4wd uses 4.875 and 5.12 gears. Probablly on the front axel like the Kia Sportage and the 87-88 Mazda B2000 trucks do. Since these are the same axel ratios as the MazdaComp sells, do you think, perchance, they are the same size ring and pinion as the first gen Rx-7? Might be an alternate source for such gears.
Page 17.
http://www.greenhouse.gov.au/fuelguide/fcg99_00.pdf
?5.83 anyone?
http://www.vintagesuzuki.com/main_ca...icktracker.htm
-bp-
08-29-02, 06:12 PM
#23
Old [Sch|F]ool
I don't know if Suzuki buys the stuff from Mazda.
Kia's Sportage is pretty much 100% Mazda, just like their original Sephia was a rebadged Protege and the Ford Festiva/Aspire was a Kia-built Mazda 121.
I don't think Suzuki also uses Mazda stuff, given that Suzuki is partially owned by GM.
There's only so many numbers of teeth you can have... for example 4.10 is a Mazda ratio as well as a ratio for practically every diff ever built in the US... same for 3.91.
Kia's Sportage is pretty much 100% Mazda, just like their original Sephia was a rebadged Protege and the Ford Festiva/Aspire was a Kia-built Mazda 121.
I don't think Suzuki also uses Mazda stuff, given that Suzuki is partially owned by GM.
There's only so many numbers of teeth you can have... for example 4.10 is a Mazda ratio as well as a ratio for practically every diff ever built in the US... same for 3.91.
08-30-02, 06:36 AM
#24
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The MSD DFIS is wiring up a Direct Fire Ignition System with a couple MSD boxes. I read it somewhere on here before, can't find the exact thread again.
I could use the 89-91 housings and just swap the front cover for the 12A one? Someone told me that 85 and earlier housings wouldn't match up with 86 and later housings. That's the reason I was using all 85 and earlier housings in the setup.
I think I'm just going to try and get a 4.3 diff, I was to go with more than 4.10, but it sounds like anything above 4.3 is to much.
I could use the 89-91 housings and just swap the front cover for the 12A one? Someone told me that 85 and earlier housings wouldn't match up with 86 and later housings. That's the reason I was using all 85 and earlier housings in the setup.
I think I'm just going to try and get a 4.3 diff, I was to go with more than 4.10, but it sounds like anything above 4.3 is to much.
08-30-02, 11:14 AM
#25
Old [Sch|F]ool
Originally posted by FastX7
The MSD DFIS is wiring up a Direct Fire Ignition System with a couple MSD boxes. I read it somewhere on here before, can't find the exact thread again.
The MSD DFIS is wiring up a Direct Fire Ignition System with a couple MSD boxes. I read it somewhere on here before, can't find the exact thread again.
You need one MSD box for the leading (it can drive two coils) and if you want one on the trailing you can do that but it would have to fire through the distributor.