diabolical1

iTrader: (3)

onepointone~

the only difference between a 12A and 13B is the rotors on a 13B are 10mm wider. the engine is therefore 20mm longer than the 12A - that and generally about 30 horsepower, when you compare the two engine with identical mods. functionally, the 13B's are a bit torquier, but the 12A can be hot. there's a post on a 12A that was running 10 seconds - just look it up.

all the parts are the same. the only parts that are different from 12A's are the e-shaft, rotors and the parts that keep the engine balanced (the front counterweight and flywheel). however, keep in mind that i'm speaking only of 74-85 13B's, the 86+ engines are a totally different animal.

for your particular project, i still stick by my original advice of sticking with a 12A because it's cheaper to port a 12A and stick it into your car, than it is to get a 13B, then port it, then get it to work in your car. it's not a hard swap, but like i said, if all you want is the experience and satisfaction from doing the job yourself, you don't need to get a 13B.

i don't know what mods you have on your car already, and with a streetport, you will need to get exhaust and you would be recommended to upgrade your intake system (carb, fuel pump, etc.) ... so you will still have to spend some money, but if you get a 13B, then you'll be buying a motor, and possibly hardware to mount it ... and that's before you get the exhaust and intake.

i gave jeremy my shpeel on 13B's because he already has a motor and i think he has some experience with this stuff already.

82streetracer~

how BIG is "big" ... i know of a streetported 4-port that runs a Haltech EFI and it was pushing around 225 HP. the 6-ports with a Dell'Orto usually push around 180 when everything is running right, but if you add the usual 20% for streetporting, then that puts it around 216 HP.

i'm just curious about this, not trying to call you out or anything like that. but i figured that the drawback to having a 6-port was the slight upset in the intake flow as the rotor ran past 5/6 ports. i don't know for sure ... this was just something i sat and thought about one day.

680RWHP12A

i like 12a's better for several reasons....1 smaller= quicker rev's, 2 they have the same bearings as a 13b =longer bearing life, stronger engine, 3 parts are cheaper!= more $ to spend other places on car, 4 easier to tune; for instance...less chance for fuel lean out problems when dealing with carburators and thier little float bowls!!! 12a 's use less gas than 13b's i have noticed when tuning, 5 12a's are cheaper to buy overall and more pleantifull.... what more could you ask for? 13b does have more torque though... the engine type depends on your budget unfortunatly but you can make 12a's fast.. 10.40 @ 134 mph on drag radials , 12 a turbo blow through stock nikki carburator, 540 whp @ 19 psi stock engine internals except ROTARYSHACK race apex seals and race oil system.... low budget racing!!!!

mperformance

you got a well detailed recipe for that? I want to bake me some 540RWHp too...

Keaponlaffen

But then you'd have to change your name to onepointthree, which doesn't look as nice...

Jeff

Manntis

the carb is independant of whether the engine is 12A or 13B, and 'easier to tune' is relative. You can tune a carb for optimum atmospheric conditions, but then drive down to the coast or up a mountain and your careful tuning is out of whack. There are those who prefer fuel injection, myself iincluded.

rx7passion

why doesnt anybody just grab a 13bt motor and rebuild that for n/a compression instead of trying to find old 70s repu truck motors?? i have never understood this...

REVHED

Agreed... this is by far the best option escpecially with later model high comp. rotors.

onepointone

i would love to put a 13bt in my car

but i dont have the money.. i think im going to pick up another 12a, port it.. and whatever else.. and swap motors in my car.. thats the best thing i can think of, for the tight bugget i have.. 13b would be cool, but i dont have the money/time to do that.. and my dad doesnt want to help me deal with putting a different engine in, he favors 12a's anyways.. so looks like 12a it is.. plus i would love to run 10's someday like in that post buts thast aLONG way down the road

onepointone

well.. im bringing this thread back from the dead


im picking up a 6port 13b out of a gslse this sunday. i got to drive that car and it seems in good condition. ive done some research on porting the 6port 13b's and alot of people dont favor it. but when you look at the second gen forum, alot of people do it. whats so bad about it and what makes it such a bitch? i definately want power, im shooting for ~160 - 180 hp, if not more.

i got the motor for $150 not including the efi setup, so im going carb. im just basically interested in why the porting is such a pain, and how doable is it?

fatboy7

It has to do with available material to port. 6 ports already have a large amount of duration added, but the sleeves limit flow, and the system has an abrupt change in flow as the rotor sweeps leaving only the 6 ports open. Basically, the 6 ports have more torque/power stock, but have a lower limit to what can be had with porting.

onepointone

this maybe far fetched (new to the 6 port setup) but can i just leave them out and have all six ports going at the same time? or will that swallow gas like crazy? what about wiring them open? what other things can be done to them naturally aspirated to make them quicker, i dont really want ot mess with a turbo setup.

diabolical1

iTrader: (3)

you'll get 180 HP just leaving it stock port. if you definitely want more, you need to figure out what your desires are and if you'll get it.

i don't want to lie, but i believe Directfreak had said (in another thread) that he got about 215 HP (flywheel) from a streetport 6PI with the stock FI system in place. so you're looking at about 35 HP if you streetport, and count on a few more HP since you'll have the carbie setup.

my advice: just put the motor in, set it up and tune it. if you're still not satisfied, then streetport it.