I will be building up a engine when i put my car away for the winter.
I have a 82 gs.
Should I stick with the 12a or should I go for a 13b
there is a second gen NA at a junkyard near me.
thats a 6 port though

Whatever I get I plan on streetporting it with a weber carb and full RB exhaust.

If I get a 13b should i get the second gen one or should I look for a 6 port.

what about ignition, dont the secondgens have distributorless.

thanks for the info

 

If you are gonna go 13b, go with a 4 port turbo. If you are gonna go with just a 6 port, you are in for a shitload more work and money for no more HP than a 12A will give you...

The 2nd gen 13b's use a CAS , instead of distrubutor. But I beleive a 12A dizzy can be retro fitted

But seriously think about it, a shitload of work for probally around 200 hp. Besides Ive heard SP on 6 ports are useless

BTW: All NA's are 6 port

 

HP potential is the same. HP is determined by the port sizes as well as the intake/exhaust systems (that part kinda goes without saying ) Airflow = HP.

The larger 13B will make is power lower in the rev range. Or, put another way, you have wind the 12A higher up to make the same power. (For the same RPM the 13B makes more power)

BTW this is true for boingers too - HP is determined by how the ports flow and the cam size, the powerband then is dictated by how large the engine is.

 

OK i figured that Bigger engine=bigger power.

plus I heard a 2nd gen with a cork sport exhaust and it sounded deep as hell, really loud and really cool. at first it looked like a apexi but i looked closer and it was a cork. I figured it was a 13b sound.

maybe my long primary RB headers with a apexi wil sound that tight and deep.

 

exhaust noise should be about the same on a 13B and on a 12A port shape being equal...

I would recommend doing a 12A...there are many factors to consider.

1st you save $ by using your current engine.

2nd 12As can make a shitload of power it just depends on what you are aiming for.

3rd 12As come 4 ports from factory

4th to put in the 13B you will need to get some other parts and have some fun with the ignition.

5th when you spank the competition you can tell them that you have the smaller engine

If you want some more power I think you can use the 12a plates and mate them to the 13B housings to make a 4 port 13B. The question is how much money are willing to spend...

I have 3 12As...and I'm happy...no need for no stinking 13Bs....j/k

 

That only works on a pre-'86 engine.

 

NOT TRUE! keep in mind the rx-4 and the 74-77 REPU came NA 13b and with 4 ports. and there are quite a few of those motors around. and i would say that they are a very good motor to build up since the ports are already larger than the turbo ones and they also interchange with 12a plates. but seriously i would go 12a, i think they last longer and they are just cool. but we have to keep our info streight on this stuff. Also if you stick the same ports in a 13 b and then do them in a 12a there is usualy only like less than 20hp difference. the larger difference is in teh tourque. the 13b has more.

CJG

 

Wind the 12A up higher

Besides the '74-78 13B 4-ports don't forget the '81-up Japanese-market carby 6-port 12As

 

[QUOTE]Originally posted by mperformance
[B]exhaust noise should be about the same on a 13B and on a 12A port shape being equal...

Trust me on this one, 12a 's are louder. if you measured the dicibles they would be close but the 12a's are so much higher pitch there is just more volumer of noise there. I ran a street ported 13b off the header and then did a 12a stock off a header and the 12a decimated it as far a as shear noise volume. then i ran my 12a pp down a set of streight pipes and trust me that was LOUD you could here it from 3 mi. away. then i got a 40" long semi truck stack muffler on it and that has quited it down a bunch.

cjg

 

Ya i forgot about those. i have yet to actualy see one though. hheea it would be kinda cool to get one.

 

Actually it's more like a 20% difference. The more mods you do, the bigger the difference in real HP.

I support the 13B if you can get it

 

on mazdatri, they sell a 4port 13b as a bolt in package for a 82-85 non se.

I have decided I am going to do something like this.
not that i dont like the sound of a 12a but a 13b sounds soooo much better plus I can get more horsepower and more low end torque.

I got the 13 b from that 2nd genNA I am going to use the rotors and Eshaft from it.
I will use the side housings from my 12a
and I will find some 74-78 13 rotor housings.(these ones bolt up to the 12 side housings.

if anyone has done thi, please give me some tips

thanx

 

I knew that was coming after I posted it, I know early 13bs were 4 port. But Ive not even seen a car much less a old 13b in good enough shape to merit building a motor from it parts

 

Jbontke has one with 26,000 miles in his rx-4 wagon.

 

[QUOTE]Originally posted by Rotortuner

Quote:

Trust me on this one, 12a 's are louder. if you measured the dicibles they would be close but the 12a's are so much higher pitch there is just more volumer of noise there. I ran a street ported 13b off the header and then did a 12a stock off a header and the 12a decimated it as far a as shear noise volume. then i ran my 12a pp down a set of streight pipes and trust me that was LOUD you could here it from 3 mi. away. then i got a 40" long semi truck stack muffler on it and that has quited it down a bunch.

cjg

I totally agree with you. The 12a can screem much louder then a 13b. I have first had experince on this one. '83 GSL(12a), '85 GSL-SE(13b), '88 TII(13b turbo).
Now the question is when I put the 20b into my '85 GSL-SE and see what it sounds like.

 

I run one in my REPU, i street ported the secondarys on it and it runs well. the old rotors that were in them lasted forever and the paltes can be changed with any 12a ones and there are a million of those around. Every thing else is interchangable. the hard part is finding the AL housings when they go bad, but if you buy them new then they cost just as much as either of the other ones. so i think they are a great motor. 3mm stock seals in them and thats kinda cool.

CJG

 

Hey, I just posted a reply on another thread about the 12a 6port! There is a guy here in Dallas that runs one, it is pretty quick! The car is actually for sale. 4k!!! coil overs, 13x8s(panasports),tokico 5-ways, panhard bar.....lots of goodys and set up!

By the way, last summer I bought 2 brand new 75' 13b rotor housings, still sealed in the plastic, still in the Mazda box for 200 for the pair!!!! They are going in my bridge port.

 

where did you get them.

I can only get the rear one from mazdatrix.

 

The rotor housings are the same. (no difference between front or rear.)

 

I saw a JDM 6-port 12a on Ebay a couple of weeks ago. It sold for $570.

I plan on going with the 12a plates and the GSL-SE rotors and housings for my next engine.

To me, that sounds like the best bet. Parts are cheap and easy to find. And, there have been a lot of folks who have had some great results.

 

Technically the rotor housings ARE different, as relates to the air injection ports. Unless you're building a smog-friendly engine for your vintage RX-4, Cosmo, or REPU, it doesn't matter

 

if the housings are the same why does mazdatrix sell them seperatly?

 

when I build this thing I will write up a walk through on how to build them.

 

20 hp in a 2200 lb car will make a noticable difference.
Plus If I use the 89NA rotors out of the engine I got I will get a higher compression. 9.7 vs 9.3 to 1

The main reason I want to do this is the the more low end torque available with a 13b and the much much much better sound they put out. it isnt so lawnmowerish sounding.