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Rotary Rebuild: 12a plates in 13b?


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Almost finished my entire build and then my motor froze over the winter. No one to blame but myself.  But this train doesn't stop.

 

-OK if you understand the title of this thread then you know rotaries... So here's my dilemma.  I tore down the motor and everything looks great except the center (intermediate) plate (iron).  The center plate gave way to the ice expansion and broke the center portion between both machined sides.  I can't find a GSL-SE center plate for sale anywhere in the lower 48 and I'm starting to lose patience! 

 

-The motor is a GSL-SE 13b, which means I can't use 86-91 13b parts. BUT I know 12a irons can be mated to the older 13b housings.  What I don't know is what are the differences between a SE 13b center plate and a 12a center plate? Would this be a simple solution or increase my headaches?  12a center plates are much more common if it's usable.

 

I know we have some knowledgeable rx7 people on here so I thought I'd post up.  Thanks all!  

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My understanding is everything is able to be mixed and matched. 
video gives some info. 

 

I would make call to someone like 

Mazdatrix who has been building rotary engines forever. Dave Lemon is one the original rotary wizards. He knows it all and a quick conversation could answer all your questions. 
https://www.mazdatrix.com

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Ah thanks for the video.  I did think of one thing though: a 12a iron won't have injector ports as 12as were all carb. I suppose I could just put larger injectors in the secondary ports, while doable that might be more changes than I care to make already.

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I have not had to buy any 13b parts in a while are plates that hard to find at a reasonable cost?   Rotor housings were always the big money. Could just weld a couple injector fittings to the manifold. Just depends on what is best compromise 

Edited by TimS
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Sounds like you understand your dilemma… they changed which housings have the water seal O-rings from the GSL-SE to the later 13B engines, and the 12A center housings don’t have injector bosses. If you want to keep what you have your only choice is to find a GSL-SE center housing, and like you say that is likely to be difficult. How desperate are you? I am going to be liquidating all my rotary stuff as I swap to a different engine, and I have one, but it is in the engine in the car with a stuck apex seal. I would have to pull the engine, disassemble it and check the housings over. They are likely to be fine, and I could make you a deal on all 3 irons already ported, with the center inlet enlarged to fit an S5 intake. I could even include a stock S5 intake, and my msq file that made 210 at the wheels

 

Since you have the engine apart here is a big tip if you are still using the red Mazda water seals. Ditch them and get some of the Atkins brown square cut Viton seals, everyone knows that you will have problems if you overheat a rotary, but with these I have had water temps over 260 several times when we had problems and the drivers kept going, I just filled it back up with water and never had a hint of a leak.

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45 minutes ago, mhr650 said:

Sounds like you understand your dilemma… they changed which housings have the water seal O-rings from the GSL-SE to the later 13B engines, and the 12A center housings don’t have injector bosses. If you want to keep what you have your only choice is to find a GSL-SE center housing, and like you say that is likely to be difficult. How desperate are you? I am going to be liquidating all my rotary stuff as I swap to a different engine, and I have one, but it is in the engine in the car with a stuck apex seal. I would have to pull the engine, disassemble it and check the housings over. They are likely to be fine, and I could make you a deal on all 3 irons already ported, with the center inlet enlarged to fit an S5 intake. I could even include a stock S5 intake, and my msq file that made 210 at the wheels

 

Since you have the engine apart here is a big tip if you are still using the red Mazda water seals. Ditch them and get some of the Atkins brown square cut Viton seals, everyone knows that you will have problems if you overheat a rotary, but with these I have had water temps over 260 several times when we had problems and the drivers kept going, I just filled it back up with water and never had a hint of a leak.

 

I was hoping you would chime in mhr650.

 

It's not a matter of cost.  I literally CAN'T find one.  

 

How desperate am I?  Look I'm deep into a 6 year "commitment bias" rebuild of my rx7.  I have done everything every forum has told me to do. Second gen subframe, and brakes, Bilsteins, on and on and on, then ECUs became free so I built my own megasquirt, gutted and rewired entire car.  Then at some point convinced myself I needed aero, so now I built my own splitter/airdam and the nine lives wing. Then I decided I NEEDED 245 tires on 10" wide wheels and that required me to push all my fenders out...

 

And after all this... my motor, which I rebuilt and ported myself and ran great... froze because of stupid water.  I just want it to run and get out on track!  And the easiest way is to just do get another center iron and put it back together.

 

And all this before the revelation of the 3400 V6 swap!    /end rant

 

Thanks for the offer on the motor too.  I'll PM you about that.

 

 

 

 

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6 hours ago, Alex3000 said:

 

I was hoping you would chime in mhr650.

 

It's not a matter of cost.  I literally CAN'T find one.  

 

How desperate am I?  Look I'm deep into a 6 year "commitment bias" rebuild of my rx7.  I have done everything every forum has told me to do. Second gen subframe, and brakes, Bilsteins, on and on and on, then ECUs became free so I built my own megasquirt, gutted and rewired entire car.  Then at some point convinced myself I needed aero, so now I built my own splitter/airdam and the nine lives wing. Then I decided I NEEDED 245 tires on 10" wide wheels and that required me to push all my fenders out...

 

And after all this... my motor, which I rebuilt and ported myself and ran great... froze because of stupid water.  I just want it to run and get out on track!  And the easiest way is to just do get another center iron and put it back together.

 

And all this before the revelation of the 3400 V6 swap!    /end rant

 

Thanks for the offer on the motor too.  I'll PM you about that.

 

 

 

 

I thought mazdaspeed still sold brand new irons for the gsl se?  Not cheap, but cheaper than an engine...

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8 hours ago, wvumtnbkr said:

I thought mazdaspeed still sold brand new irons for the gsl se?  Not cheap, but cheaper than an engine...

 

Sorry, I said it's not a matter of cost, and I lied. Not dropping 800 bucks each on new plates :)

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13b parts (86 through 91) are still fairly easy to get.

 

Mazda still makes them (or did as of about a year ago when I last checked).

 

The 12a engine parts are NOT being made any longer.

 

13b GSL se parts were never easy to find.

 

The engine seems to be falling out of favor except for people who just want to have a rotary.

 

With the ecotec and other small light engines making more and easier power they just don't make a lot of sense anymore.

 

Too bad, cause I really like SOME of their charcteristics!

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6 hours ago, Alex3000 said:

 

Sorry, I said it's not a matter of cost, and I lied. Not dropping 800 bucks each on new plates :)

Why not just swap in a 13b from a 2nd gen?  You can use factory parts to bolt it in.

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2 hours ago, wvumtnbkr said:

13b parts (86 through 91) are still fairly easy to get.

 

Mazda still makes them (or did as of about a year ago when I last checked).

 

The 12a engine parts are NOT being made any longer.

 

13b GSL se parts were never easy to find.

 

The engine seems to be falling out of favor except for people who just want to have a rotary.

 

With the ecotec and other small light engines making more and easier power they just don't make a lot of sense anymore.

 

Too bad, cause I really like SOME of their charcteristics!

 

That is my plan, build a fresh engine with all my best stuff, up to and including ceramic apex seals. Spend some time on the dyno tuning and getting a big power number, then sell everything to a rotary fanatic who can use it for track days or autocross.

 

Then move on to a nice lightweight aluminum 4 cylinder engine.

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5 hours ago, wvumtnbkr said:

Why not just swap in a 13b from a 2nd gen?  You can use factory parts to bolt it in.

If this had happened 2-3 years ago I would have all the rx-8 eshafts and s5 rotors up the wazoo on this rebuild.  

 

My issue is right now I just need this thing to run and see if the whole car works. I'm done with projects. I just want to be at the track.

 

 

 

 

 

 

 

........*And I'm about 90% ready to cut my losses and throw down money on a turnkey e36.

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3 hours ago, mhr650 said:

 

That is my plan, build a fresh engine with all my best stuff, up to and including ceramic apex seals. Spend some time on the dyno tuning and getting a big power number, then sell everything to a rotary fanatic who can use it for track days or autocross.

 

Then move on to a nice lightweight aluminum 4 cylinder engine.

 

Good plan but you really don't need the ceramic apex seals for a normally aspirated rotary.  I realize it may get you few extra bucks on the sale but at a very steep initial cost.

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1 minute ago, Alex3000 said:

If this had happened 2-3 years ago I would have all the rx-8 eshafts and s5 rotors up the wazoo on this rebuild.  

 

My issue is right now I just need this thing to run and see if the whole car works. I'm done with projects. I just want to be at the track.

 

 

 

 

 

 

 

........*And I'm about 90% ready to cut my losses and throw down money on a turnkey e36.

 

I understand completely.  Had my own well documented engine woes.  I finally gave up the piece togethered engine project and found a reputable and reliable builder, thanks @Chris Huggins, and paid the money.  Eliminated one big issue straight away.  Sounds like you can build it so might be better in the long run to buy the piece that is available eventhough it may come with a steep cost initially.  In the end it will be a drop in the sea.  I do feel your pain.

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Related topic that those in this thread should know something about. How much is a FC subframe and steering swap costing in points nowadays? I plan to build my own crossmember but it would be interesting to know what the guys with FC swaps have seen.

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13 hours ago, TimS said:

 

I understand completely.  Had my own well documented engine woes.  I finally gave up the piece togethered engine project and found a reputable and reliable builder, thanks @Chris Huggins, and paid the money.  Eliminated one big issue straight away.  Sounds like you can build it so might be better in the long run to buy the piece that is available eventhough it may come with a steep cost initially.  In the end it will be a drop in the sea.  I do feel your pain.

 

You see, I'm getting to that age where I'm finding I just have to start paying for things and letting it go.  It's a difficult mental transition from "I can and will do everything and anything and everyone is a sucker!"  mentality.

 

- Also, for context, I took my nice stock street car s2000 to summit point and on the last session of the weekend looked in my rearview to see a cloud of blue smoke behind me... So I need to figure that motor out.  Still pissed at myself for that.

 

- Oh yeah and I went from being a DINK to having twins.... So I went from working on cars all weekend and night to now I have to sneak to the garage for a few hours and even that gets me side eye.

 

1 hour ago, mhr650 said:

Related topic that those in this thread should know something about. How much is a FC subframe and steering swap costing in points nowadays? I plan to build my own crossmember but it would be interesting to know what the guys with FC swaps have seen.

 

While I very much wonder about this answer, my general feeling with all the crazy rx7 stuff rx7 teams is that its all a bit don't ask don't tell.  But maybe I have that wrong ;) 

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22 minutes ago, Alex3000 said:

You see, I'm getting to that age where I'm finding I just have to start paying for things and letting it go.  It's a difficult mental transition from "I can and will do everything and anything and everyone is a sucker!"  mentality.


This is definitely a difficult transition to make. I’m working on this subject myself. I finally decided I want to drive more wrench less. 

 

22 minutes ago, Alex3000 said:

Oh yeah and I went from being a DINK to having twins.... So I went from working on cars all weekend and night to now I have to sneak to the garage for a few hours and even that gets me side eye.

 

Thankfully my daughter is now 15 and doesn’t want me around, so the side eye is not as piercing as it once was. Good luck on that front. 

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15 hours ago, TimS said:

 

Good plan but you really don't need the ceramic apex seals for a normally aspirated rotary.  I realize it may get you few extra bucks on the sale but at a very steep initial cost.

 

If you race a car with 787 on the door, the ceramic apex seals fit, I believe that may have been the first time ceramic seals were used.

 

The highish price, I got a smoking deal, was paid 5 years ago so there I no good reason to let them continue to gather dust.

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2 hours ago, Alex3000 said:

 

While I very much wonder about this answer, my general feeling with all the crazy rx7 stuff rx7 teams is that its all a bit don't ask don't tell.  But maybe I have that wrong ;) 

I can tell you that WE do not operate that way!

 

My builds were both documented on this forum and I help any racer I can, even with setup stuff that was hard earned.

 

As far as the subframe swap....  We did that under the old rules.  We aren't sure exactly how it is going to be valued.

 

It was at 110 pts before.  Control arms (20 pts).  Spindles (20 pts).  Subframe (10 pts).  Swaybar (30 pts). Rack and pinion (30 pts)

 

The points values have all changed now.  I would still take points for control arms, swaybar, spindle, hubs, and subframe.  I think it would end up right around 80 pts.  Mainly due to swaybar being much cheaper, and rack could be considered free?  Maybe?

 

The way we did it, was to notch the frame rails so the subframe sits at the correct height.  Iirc, you need to cut them about 3/4" and then plate them so the subframe sits "up" inside the framerails.

 

Edit to say that this was done on an fb rx7 with fc subframe.  We were swapping in a 13b and it was just as much work to do it either way and this way got the better suspension, steering, and brakes.

 

Edit #2...  if you already have a GSL se engine in the car, the s4 or s5 13b will bolt right in place in your car if you use the GSL se mounts, oil pan, and front cover.   The only thing you need to figure out is that the lower intake manifold will not bolt to the s4 6 port engine.  You MAY be able to mix and match manifolds (for points) to join the parts together and use your GSL se engine stuff.

 

Or, if you are already MS, just use that and ask tech about which manifolds they want you to run.  It will depend if they consider an s4 13b a swap.  The line for 13b 1st gens says just that....  it's a bit confusing tbh.

Edited by wvumtnbkr
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2 hours ago, mhr650 said:

 

If you race a car with 787 on the door, the ceramic apex seals fit, I believe that may have been the first time ceramic seals were used.

 

The highish price, I got a smoking deal, was paid 5 years ago so there I no good reason to let them continue to gather dust.


I believe the ceramic apex seals were developed earlier than the 787. I think some of the early IMSA GTU and GTO cars were built with those apex seals. A great friend who built every rotary I have raced would tell me stories of rebuilding engines in his hotel room at Daytona. He had a Polaroid of a table with everything spread out. This would have been in the early 80s. Drummond, Downing, or Mandeville were probably using these when they were dominating GTU and GTO. 
 

If you have them already then I would use them for sure. Always a great selling tool as well if you plan to sell the engine at some point. 

Edited by TimS
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18 minutes ago, wvumtnbkr said:

I want that!

 

Me too.  That car was great fun.  Not super fast but really great fun.  Solid no rust RX2.  That pic is the in field of the Las Vegas roval.  Leading a corvette and an NSX or maybe getting lapped.  Friend of mine sent it to me a few days ago.  Not sure how or where he found the pic.

Edited by TimS
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