vj226966

As some as you guys may know my 12a crapped out on me a few months back and now the rebuild begins. I just landed a 1985 4 port 13b with a fresh rebuild with 3mm seals and such. It is street ported. I will be running a Racing Beat intake and Racing Beat header along with a Holley 650 carb. I have a few questions, will i have to change flywheel and clutch? I will be using my 79 5 speed tranny. Can i use my old starter? Most of all what kind of performance gain would i see from my stock 12a with a Holley 465 and Racing Beat intake with header?What carb jets should i use and what are you guys using that has a similar set up?

flight_of_pain

The 85 13b is 6-port, without seeing pics, I would guess you have -se rotating assy. and housings between 12a or old school 13b irons. Up to 1985 all rotor weights used the same flywheel weights, so you will need an -se flywheel/PP. It will bolt up to your 12a trans no problem, but will require slotting the motor mount ears.

You will like this motor, I guarantee it.

Isaac
(running a 4-port 13b, huge SP, modded nikki, race header)

vj226966

Thanks for the reply. I bought this motor of of this forum. I you look up 1st gen parts for sale you will see the post it says 1985 gsle part out or something like that. He has a vid of it. Check it out and let me know what you think.He said it was a 4 port so he may have used diffrent parts i guess. This man knows his Rotarys so i dont doubt him one bit. I am hoping it comes with the flywheel at least. If it does then does that still mean i need to change clutch and pressure plate?It comes with the front mount so that is not a issue.

Rx-7Doctor

iTrader: (13)

All I have to say is, "How many times do we have to go over the same stuff"?

Been covered a billion times so lets just clutter up the technical section with more of the same stuff! :-(

vj226966

If the archives and the search options would pull up what i am looking for i would not post. I did search. I typed in 13b in 1st Gen Rx7, 13b in 1979 rx7 and so on. You type in what i did and see what you come up with.

Rx-7Doctor

iTrader: (13)

How about 13b swap? Also flywheel? It's all there, you just need to know what words to use.

vj226966

I am sorry if i used the wrong words i was trying to be specific, not using such a broad search, sorry.

Rx-7Doctor

iTrader: (13)

Not a biggie. It's just that if we are going to improve and keep the section as informative and easier to use we have to put forth the effort to learn how to use what we have in place.

whistlepig87

iTrader: (2)

The doctor is right that if you look harder, the info is there, it is a bit scattered and most of the threads I find are not complete instructions like a step-by-step book. It will take time, when I had something I needed to find, I took notes and compiled my own handwritten list of parts, steps, further research, etc. I found it to be tedious, frustrating at times, and not always 100% correct info...So be careful what you believe, back up your notes with multiple sources. Do you think it is wise to begin an entire motor swap based on info from an online forum?

I want to do exactly what you are planning to do, but I am years away. I rebuilt a 12A to start, and I learned so very much by doing that, I am much more comfortable with modifying my car through my hands on experience.

Good luck!

vj226966

Thanks for the Good Luck wishes.I am not doing this swap on info from a forum, my car took a crap and i have been a member since i got my Sa, and i saw the motor on here. I was at firstjust going to rebuild my 12a. After seeing all of these RX7s with 13bs, GSLSE , and some other 7s with them i said heck ya.I have read alot of people with Turbos, not that many just with a carb. I would like to get input from as many as possible thats all. I did do the search of 13b swap, and found 1 point that i needed, out of i think 6 pages. I would just like to thank all that have helped me with my old 12a.

whistlepig87

iTrader: (2)

Great! I am jealous, I can't wait to do a 13b swap, but I am getting married and I would probably ruin that if I blew more money on my car right now...Women
I think you will not only be very happy with the engine, tracking down parts will be easier, given that rebuildable 12A housings are like precious gems now.

apremdas

Hi,
I had my 1982 12A engine swapped out for a 13B 6 Street Ported engine. I had someone else out west do the work so I'm not too up on the technical side but I do know that they shortened the drive shaft, adjusted the engine mounts, mated the engine to a 1984 transmission since the 12A original transmission would not fit directly. I had all this done about 20+years ago. Still running like a charm. I absolutely will never get rid of my RX7. The shop that did the work also experimented with (at the time) a setup involving 2 MSD 6AL Digital boxes with a 3 wire on the distributor. It's like having one digital box dedicated tothe primary and one box dedicated to the secondary. It's supposed to be more effecient in terms of burning - about 95+ % burn. I've got 4-11 rear pinion gears, 44mmPHH Mikuni Carb side draft and overall, the car sems quite impressive. The car was driven on the Calgary race track (oval track) and did 160MPH. It would have done more but because of the oval track it would run out of banking. The driver figured it would do about 10MPH or so more.
So overall, real happy with the 13B swap. Oh, a larger fuel pump (Carter) was also put in to accomodate the fuel requirement under race conditions.

Rx-7Doctor

iTrader: (13)

Sorry but I believe your shop didn't have a clue as to what they were doing.

#1- Their is no need to shorten the drive shaft.
#2- The transmissions bolt up with no modification.

160 MPH?


I don't think so.

flight_of_pain

He said Calgary, so perhaps KPH On a side note, I can max out the speedo in my FB, which is 145mph (+/- 10% is 130-160mph)

Isaac

vj226966

Thanks man. My wife hates my 7. I paid 2400.00 for it and only drove it for a couple of months and it died. So me spending money on it is a bad thing.In her eyes. LOL. I have a few maybe rebuildable 12a housings laying around. I just like the thought of some extra hp with the 13b. My 12a was a blast, but more is always better. Its never enough.

whistlepig87

iTrader: (2)

You would need 250hp and it geared right to make it plausible to hit 160mph... Power is related to velocity cubed when you only look at drag power. It takes about 150 hp just to overcome drag at that speed, assuming .3-.35 Cd that Mazda advertised that the car had. That doesn't count rolling resistance and internal resistances in the engine/drivetrain. I don't even know if you could get that out of an N/A 13b, but I don't see 100hp gain over stock with an exhaust and intake, or even a streetport, I think you'd need forced induction to help. Also, when you switch out a differential, won't that effect your speedo? He did have a 4.11 in there, so maybe the dial said 160....but reality told another story.

82FanTC

iTrader: (9)

4.11 gears would affect RPMs related to MPH but the spedometer would still be accurate. Tire/wheel size can have an effect on accuracy of the spedometer

PercentSevenC

No, it wouldn't. The speedo cable goes to the transmission, so rear-end gears will affect the reading.

jshiz

iTrader: (4)

I can max out my speedo with the 12a.... too bad it only goes up to 85...

vj226966

I almost maxed my speedo in my 79, i Got to 120ish it it shook me to bad, old car, its a 79, 30 some years old, scary. Funny thing it wanted to keep going. That lil 12a was strong.

PercentSevenC

I wrapped the speedo in my old rotary GLC back around to 0. Granted, the numbers only went to like 90 or something.

whistlepig87

iTrader: (2)

You guys are crazy....lol