dbragg

iTrader: (7)

i have a 76' 13b with 2000 miles on a mazda rebuild. i was planning on selling it and purchasing a streetported 12 or 13b near me, depending on how much cash i could come up with. im wanting to get rid of the 76 13b due to its lower power i suspect are due to its low compression. after thinking, wouldnt this be a good engine to use if i just got a set of higher compression rotors installed(GSLSE,89-91, or rx8 if possible)? or if i wanted to go for boost ive always heard the 4 port 13b is the best way to go, so i could use the low compression rotors and boost it pretty high? just need some help guess so i can make up my mind in what to do.

SS124A

rotor weight is often more important than compression ratio in a rotary.

An S5/S6 turbo engine set-up with proper exhaust, and induction would blow you mind.

remember flame front id also key.

BTW, the GSL-SE rotors are the same.
all 76-85 13B rotors use the same comp ratio, and rotor weight,.

another point is to consider the 12A.. which peaks at a compression of 9.2:1.... much lower than the 9.7 of the S5 N/A

market this engine to someone doing a REPU resto..

build an engine using R5 outer and a y5 intermedate housings... and GSL-SE rotor housings... or go 12A... in which case let me know, I have a Mazda Part number for you.,

Midwest 7's

iTrader: (4)

why dont you get yourself some S5 rotors and rebuild the 76?

Jeff20B

iTrader: (13)

I'd recommend keeping the engine. I'm going to do a rebuild on a '78 RX-4 engine, which is identical to a '76 engine internally, as far as I know. Keep it.

nick1

does it need a rebuild?

dbragg

iTrader: (7)

to clear up any confusion, in my original post where i state "due to its low compression" i dont mean the engine is bad, i am referring to the compression the engine has stock.

nikc1-
no it definately doesnt need a rebuild at all. its just been rebuilt by mazda. i was just thinking about tearing it down and using S5 n/a rotors, getting it pinned, maybe better apex seals, getting some port work done, and anything else i might decide or am informed i should do.

ss124a-
i know this is probably a dumb question, but what is r5 and y5? why GSLSE rotor housing? everything ive read always says the 2nd gen 4 port housing are the way to go. i had a list telling all about pretty much every rotory car mazda made. it said the engine was in the REPU and the RX4. on the list it said the compression on the 76 was i think 9.2:1 and it only had 110 hp and 120 tq. for the GSLSE i remember it saying the compression was 9.4:1 and it had 135ho and i think 133 tq. i assumed the higher numbers would be due to its 6port and its higher compression. the list also stated that the 84 12a compression was i believe 9.4:1. maybe this list was just full of bad info, i dotn know. but thats what i have been basing a lot of stuff off of. i want the engine to be strong, but i cant decide if i want to go 12a or 13b. i will probably do 13b since i have one with around 2000 miles on it and i cant seem to sale it for anything else. im not even sure what apex seals this engine has, i would have to guess 3mm, but im not sure. i think my best route would be to take it to a shop along with some S5 rotors, and maybe some stronger apex seals. since the engine will be taken apart will it need a rebuild kit to use while rebuilding it or would the stuff on it now be ok? also is there anything else you think i might need to do, or any other information i might should have? thanks.

i have just searched and i have found the list i was referring to, here is a link to it:

http://www.monito.com/wankel/engines.html

SS124A

you have some bad numbers.,

the way I see it you have a few options.

keep it the way it is.

tear it down, port the **** out of it, and re-assemble using an S5 rotating assembly.

sell it,
then build an engine from scratch.

All 74-85 Mazda Rotaries... 12A(B) and 13B used the 3mm seals.

PM me if you like I can give you my number and I can go further in depth on this.
it would take alot of typing to have a full-on Mazda interchange post...

although we should start one as an FAQ sorta deal... if there isn't one already.,

dbragg

iTrader: (7)

well i think you have helped me decide what i will do. i will first try to sale the engine, and if i cant i will buy the internals from an S5 and then get it ported and pinned. all i will need from the S5 is the rotors and eccentric shaft right? but like i asked previously, will i need a rebuild kit for all the seals and stuff? i dont want the guy at the shop telling me ill need to bring one and me buying it if in fact i wont need to.

SS124A

what shop are you talking about?

why not consider going 12A while you are at it? what will you be using for induction? what will the exhaust comprise of?

has anyone gotten the newest issue of RX-tuner?


If you go 13B...Optimally you will obtain a full rotating assembly from an S5 auto.... I do not consider the e-shaft part of the rotating assembly. "pretty much" all 13B e-shafts are interchangable... (anyone who flames me on that is an idiot who doesn't understand I am over-simplifying this conversation)

you are opening up a huge can of worms here with many many options.


lets first determine what you plan to use the car for... then we can go from there.

Midwest 7's

iTrader: (4)

what is included in the full rotating assembly? does thet include all the bearings and **** on front or just the front and rear counterweights?

dbragg

iTrader: (7)

well its an SA with GSLSE suspension conversion, lowering springs, adjustable shock and struts, and upgraded sway bars(rear is 3-way adjustable). so it would definately be funt to drive. i dont want to make it a full race car though because the car is in such good condition, interior is perfect, so id hate to strip it out. im pretty much wanting to make a toy. something i can bring out every so often and just have fun with. take it to the road course every once in a while, drag way once or twice. just basically an all around toy. i dont want to go all out on the engine so that it would be a task to handle. i just want it to have some "*****" or whatever. basically speed wise id hope to run in the 14's in a 1/4. i plan on just using a carb for induction purposes. right now i have a holley 465 to go on it, but i want thinking about going side draft. maybe later on down the road upgrading to throttle body kits i saw a company makes for 7s somewhere on the net. i havent got a single rx tuner, but i plan on subscribing either tonight, or next week. i have no problem with going 12a, i just thought itd be easier to get the power and all with a 13b

SS124A

I consider a full rotating assembly to be an either factory matched, or machine matched set of front and rear counterweights (and/or flywheel) and the rotor pair or trio

when it comes to e-shafts there are a few little things I look for when matching journals to bearings.... so i could go through 5 or 6 e-shafts when selecting one for a specific build.

SS124A

sorry, just saw another reply... so I'll post another.

I would personally go with an extend ported 12A. with a big weber.


something like a 48 DCO, or 48IDA.

these can be made to be very streetable.. and on track they are amazing,

I have the same set-up.... while on track at IRP during Rev there were like 2 cars (an A-spec tuned FD, and a TII with an Engine by AIM) during my session that could keep up in a straight line..( I was having hardcore suspension issues so corner was a different issue... )


I suggest you give Shane or Clinton a call at AIM Tuning. this is were my engine, and that other TII engine was from.... their number is 317-381-0898

I asked about the RX-tuner because they have finally advertised in there.

If you go this route I can tell you exactly what carb setting and jetting to use.

I can e-mail you a video of my car an an autoX so you can hear it on "track"

Midwest 7's

iTrader: (4)

how do you match the front and rear counterweights? the rotors have either a,b,c,d, or e on them and they need to be idealy the same or within one or two right?

dbragg

iTrader: (7)

email me that video at aws140@hotmail.com

when you say extend ported what do you mean?

i would definately go 12a, but that means i have to sale the 13b to help fund it. but everyone who is interested wants to trade me a 12a with 60k or 80k straight up. that just doesnt seem fair to me since mine only have 2k

SS124A

e-mail sent..

Don't trade them straight up... that is retarded....

if you can get a 84/85 12A auto for a PARTIAL trade with some cash, then that would be ok..

you would be in essence using that 12A as a core.

dbragg

iTrader: (7)

i was told by the guy at that shop i talk to that the auto would be the way to go, why? he said something about a weight or balance

dbragg

iTrader: (7)

i didnt get the video.

Hades12

Me, I would just Give the 13b a nice Street port and button it back up.

Buddy of mine that got me into 7's had an 81 with a 76 cosmo 13B Mukuni 44 and the thing would haul ***. The only car he ever really lost to was an SS camaro. His first speeding ticket was a 151 in a 55 in that car.

dbragg

iTrader: (7)

if that was all he had done to the car. that had to be one heck of a port job. SS cameros run low 14's-mid 13's depending on the driver

diabolical1

iTrader: (3)

his numbers seem fine according to Mazda ...

SS124A

Lets not argue over semantics... I'll try to find and post my sources... maybe i have the wrong info...

the important thing, as i have said before... rotor weight/balance and flame front can prove to be more important than CR.

E.G.

HEMI engines... they maintain a better flame front... therefore producing more power.... (all other things being equal)

BlastinSideways12A

Mazdatrix has all the rotor weight and compression numbers. Its not a good idea to mix pre-85 rotors with 86+ housings or vice versa. The shape of the housings are ever so slightly different. Don't worry as much about compression. IF you ever were to tear the engine down which I wouldn't do unless something unfortunate were to happen to it, I would use GSL-SE rotors since they are 9.4:1 and streetport the engine but for now I would just do all bolt-ons. You'd be VERY pleased with the results that you'd get just from bolt-ons to an older model rotary.

Use the engine as is, get Racing Beat Street Port exhaust, DLIDFIS ignition, Lightweight flywheel, and a Weber DCOE 48 carb. I have this setup on my 85 GSL (83 12A engine) except for the flywheel and I love it. A 13B should give you that little extra torque but still be very similar to my 12A setup. Don't tear apart that engine, especially since nothing is wrong with it.

BlastinSideways12A

BTW, that engine in a first gen RX7 with the setup I just stated will run low 15s with full interior if you tune the carb correctly. Maybe even 14s since you have limited slip and if you get good tires.

dbragg

iTrader: (7)

thanks blastinsideways12a, im glad to know that the S5 rotors may cause a problem. i think ill go ahead and get my hands on a set of GSLSE rotors just to have if i ever decide to do it. but for now i think im going to do what you are talking about. the engine has all emissions removed, a lightened flywheel already, and a holley 465. i have already planned on doing the ignition set up and i hoped to be able to get my hands on a webber or some other sort of sidedraft carb.