FCKing1995

iTrader: (3)

Sorry to ask such a question. It has been quite a few years since I have posted here, as I haven't had a running RX7 in a long time, but still have one of my loved FB's that I am finally trying to get back in street worthy condition. I bought it from a guy I know about 3 years ago with intent of swapping a 12A from another FB I had and have since scrapped and sold for scrap metal, and making it run. I ran into troubles and after putting in the engine, I left it to sit under a tarp for the last 3 years. Prior to me getting it, it had sat for 8 years in his garage without moving, so it hasn't seen the road in well over a decade. It's a shame really.

ANYWAY, to my question. In order to save my 12A Racing Beat full streetport exhaust system, I would like to maybe hack off the 12A flange and re-flange it with a 13B flange so I can drop in a 13B. How "off" are the spacings of port between 12A and 13B engines? Do you think the 12A header piping would be suitably large enough for a 13B. Difference isn't much in terms of air flow between a 12A and 13B.

This been done by anyone here before? Again, sorry for this noobish question. It's been a long time, and it will take me a little time to get back into the swing of things. I have forgotten a lot of knowledge I used to have.

rx71king

iTrader: (6)

cut your header flange in half and cut the front pipe and ad 10mm to it...

broke7

iTrader: (1)

It is a easy fix. I would just cut the 12a flange in half and use it. Just weld it up on the new engine and use it for the fixture

orion84gsl

iTrader: (5)

Dj55b did this for me last year. Enjoy.

https://www.rx7club.com/1st-generation-specific-1979-1985-18/how-modifiy-12a-header-fit-13b-engine-907195/

rx71king

iTrader: (6)

peejay way looks eazyer..

peejay

Well....

On the headers I modified, it was a good solid 3 or 4 hours of work with the rotary file to oblong the holes and open the ports out to fit the 13B engine. (Steel is freakin' difficult to work compared to iron or aluminum) Even then, I later discovered that I was off a little bit and there was some overhang on the front port.

I recently acquired a 12A "road race" Racing Beat header. Unlike my current headers, which are two feet of solid curves each, these ones have a small straight section before the end flange. I used a handheld bandsaw (best. tool. ever.) to cut the #2 tube off flush with the flange, then cut the bead of weld off of the tube, used a chisel to pop the rest of the tube out of the flange, bolted the mess to a 13B that I had lying around, and welded it back together. Total time, 1/2 hour.

So "easier" will all depend on what header you have, and the tools you have at your disposal. Mind you, if you don't have any of those tools, you can buy a new header for less than the tools cost. (But then again it's the flip side of the "all your problems look like nails" thing)

Of course, while I was working, I noted that the RB header's tubes are physically smaller than the exhaust ports, so it looks like I still have three or four hours' worth of grinding to do to the headers!

FCKing1995

iTrader: (3)

Thanks fellas. So the bolt pattern is the same, just flange spacing changed. That is good to know.

Eventually I want to get this car close to how my black FB used to be, which is simple. I have a Mikuni 44mm carb and 1 piece manifold standing by from my previous FB, also 12A, so I suppose I will either have to modify that too, or just get a 13B manifold. I want to keep the RB road race exhaust of course, then do away with everything under the hood unnecessary for the car to run. My black FB had very little left, but still ran well enough for daily driving. I always had an issue though, which I think was fuel pump related. At anything above half throttle, I would get tons of hesitation and bogging and a misfire, what clearly felt like a fuel issue. It was running on the stock pump and I always assumed it was in need of a good, new pump. I picked up and appropriate low pressure fuel pump, but never got around to installing it. As long as I can get this thing road worthy, I will be happy, and can start modifying from there. Needs a bit of work though. The brakes are fully rusted to the point of being seized. One of the rear sway bar mounts is snapped off, but I think I can go without the rear sway without issue, since I see many people running without them. Needs a bit of body work, a small dent in the rear right corner above the tail light, tough to pull out, as well as a smashed right tail light cover, missing front header panel between the headlights, a cracked windshield and some minor side trim issues. All cosmetic, of which I can deal with.

FCKing1995

iTrader: (3)

While I'm asking. What are the odds that after sitting for 3-4 years without running or being turned over, with open intake and exhaust ports, sitting outside under a tarp, that a 12A would still run? I would imagine seals are seized, and rust is forming on some of the internal surfaces. I'm going to try and make this 12A run first, just for the sake of trying. If I can make it run I may just stick with it for a while, but I doubt it will run like I want it to.

j9fd3s

iTrader: (3)

ymmv! the metering oil does put a thin coating of oil all over the inside of the engine, but not sure how long that would last.

best bet is to squirt lots of light oil in it, and spin it over gently, to get it all spread, and then see if its got compression