Dead 12A pics
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Super Newbie
Joined: Feb 2001
Posts: 4,398
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From: Birmingham, AL
Dead 12A pics
Last year about this time, rx7passion helped me pull the enigne out of my car so we could do some major oil leak repairs.
I was degreasing the engine, and unbeknownst to me, I got some water in the combustion chamber. (I'm an idiot)
Anyhow, the engine got hydrolocked because of that, and it "popped" free. This worried me. Naturally, the car wouldn't start. A compression check revealed 0 psi on the rear, 35 on the front. Not really a big deal to me, the engine never seemed to have the power it should have had anyway.
So I got a (damn good running, I must add
) 12A from Fire85GSLSE to get the car running, while I was deciding what to do next. I was going to pull the old engine apart and rebuild it. Here are some somewhat ok pictures of it.
Rear plate:
Center plate:
Front plate:
Rotors (note the stuck apex, corner, and side seals):
I was degreasing the engine, and unbeknownst to me, I got some water in the combustion chamber. (I'm an idiot)
Anyhow, the engine got hydrolocked because of that, and it "popped" free. This worried me. Naturally, the car wouldn't start. A compression check revealed 0 psi on the rear, 35 on the front. Not really a big deal to me, the engine never seemed to have the power it should have had anyway.
So I got a (damn good running, I must add
) 12A from Fire85GSLSE to get the car running, while I was deciding what to do next. I was going to pull the old engine apart and rebuild it. Here are some somewhat ok pictures of it. Rear plate:
Center plate:
Front plate:
Rotors (note the stuck apex, corner, and side seals):
Thread Starter
Super Newbie
Joined: Feb 2001
Posts: 4,398
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From: Birmingham, AL
more:
Rotors again:
I think I see the reason it never ran as well as it should have (massive chrome flaking on the rear rotor housing):
The front rotor housing wasn't that much better off:
What an NA FC is good for, storing parts (just kidding)
At first glance I thought I was going to get away with just porting it, cleaning it all and slapping it back together with new gaskets, then I saw the rotor housings
Rotors again:
I think I see the reason it never ran as well as it should have (massive chrome flaking on the rear rotor housing):
The front rotor housing wasn't that much better off:
What an NA FC is good for, storing parts (just kidding
)At first glance I thought I was going to get away with just porting it, cleaning it all and slapping it back together with new gaskets, then I saw the rotor housings
Joined: Mar 2001
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From: https://www2.mazda.com/en/100th/
i have a 12a just like that! we got a 12a core back that actually didn't have broken apex seals, so i took it apart hoping it blew a water seal or something, but it looks just like that one.
i think they peel because the engine runs a little hot for a long time.
mike
i think they peel because the engine runs a little hot for a long time.
mike
Old [Sch|F]ool
Joined: May 2001
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From: Cleveland, Ohio, USA
I think it's 'cos of higher revs.
My rotor housings were PERFECT in the Quasi-Evil Engine. 23k many high-revved miles later, the housing that wasn't demolished was showing some flaking along one outer edge and the chrome along the middle was very "rippled" looking. Essentially, both housings are junk.
My rotor housings were PERFECT in the Quasi-Evil Engine. 23k many high-revved miles later, the housing that wasn't demolished was showing some flaking along one outer edge and the chrome along the middle was very "rippled" looking. Essentially, both housings are junk.
Are you Nucking Futs?
Joined: May 2001
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From: Abilene, TEXAS
I have heard some people use the housings even with minor flaking. I do not know what the danger is in this but it is supposedly much cheaper. I do know that most commercial engine builders will not use a housing with even minor flaking. Any thoughts?
I'd use housings with minor flaking. I took a core 12A apart last year that had overheated and there is a little flaking. If they haven't been crushed they may be reusable. The parts that are dead though are all three side housings. The metal at the bottom is blued and can be scraped away with a box-cutter style razor blade. OUCH! I eventually got all the seals out of the rotors, but I think the whole thing is done-for. Did I mention the engine sat out in the rain for an extended period? It was full of water and very rusty but amazingly still turned a little by hand.
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Tennis, anyone
Joined: Jun 2001
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From: SoCal.
Hey felix, when you do porting on your 12a, do you use
a template, or do you just kinda " dress " the ports ??
Also when porting do you use a stone wheel, or a metal
rotory file bit(s). I've been getting ready to do the same
thing,... pull engine to repair oil leak(s) and re o-rings.
I'll be useing air tools and have been buying all kinds of
rotory file bits for both the dremmel and the air tool.
I'm still doing as much research as i can ( asking stupid
questions ) about porting, gaskets,templates,port shapes, I've had the 7 for almost 2 years now, and i
must admit " that **** still baffles me " and anything with
pistons is easy. I've done alot of porting (heads) on
ford V8's s.b. b.b. V6's 2600,2800,inline 6's 170,200, 240,250,300's and 4's 2000,2300's both alloy and cast iron. so i'm hip (sorta) can you throw some tips and,,
what to,,and what not to's at me ? about porting the rotory engine ?. I'm in no hurry,the 7 runs real good.
the miles are getting up there, so not to far off in the future it will need some help,but i would like to do the work before the engine fails, or apex seal goes. It's the
oem engine from 1982 with 140.000 miles... thanks man
a template, or do you just kinda " dress " the ports ??
Also when porting do you use a stone wheel, or a metal
rotory file bit(s). I've been getting ready to do the same
thing,... pull engine to repair oil leak(s) and re o-rings.
I'll be useing air tools and have been buying all kinds of
rotory file bits for both the dremmel and the air tool.
I'm still doing as much research as i can ( asking stupid
questions ) about porting, gaskets,templates,port shapes, I've had the 7 for almost 2 years now, and i
must admit " that **** still baffles me " and anything with
pistons is easy. I've done alot of porting (heads) on
ford V8's s.b. b.b. V6's 2600,2800,inline 6's 170,200, 240,250,300's and 4's 2000,2300's both alloy and cast iron. so i'm hip (sorta) can you throw some tips and,,
what to,,and what not to's at me ? about porting the rotory engine ?. I'm in no hurry,the 7 runs real good.
the miles are getting up there, so not to far off in the future it will need some help,but i would like to do the work before the engine fails, or apex seal goes. It's the
oem engine from 1982 with 140.000 miles... thanks man
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From: everywhere
Originally posted by Jeff20B
I'd use housings with minor flaking. I took a core 12A apart last year that had overheated and there is a little flaking. If they haven't been crushed they may be reusable. The parts that are dead though are all three side housings. The metal at the bottom is blued and can be scraped away with a box-cutter style razor blade. OUCH! I eventually got all the seals out of the rotors, but I think the whole thing is done-for. Did I mention the engine sat out in the rain for an extended period? It was full of water and very rusty but amazingly still turned a little by hand.
I'd use housings with minor flaking. I took a core 12A apart last year that had overheated and there is a little flaking. If they haven't been crushed they may be reusable. The parts that are dead though are all three side housings. The metal at the bottom is blued and can be scraped away with a box-cutter style razor blade. OUCH! I eventually got all the seals out of the rotors, but I think the whole thing is done-for. Did I mention the engine sat out in the rain for an extended period? It was full of water and very rusty but amazingly still turned a little by hand.
Joined: Mar 2001
Posts: 31,835
Likes: 3,232
From: https://www2.mazda.com/en/100th/
Originally posted by peejay
I think it's 'cos of higher revs.
My rotor housings were PERFECT in the Quasi-Evil Engine. 23k many high-revved miles later, the housing that wasn't demolished was showing some flaking along one outer edge and the chrome along the middle was very "rippled" looking. Essentially, both housings are junk.
I think it's 'cos of higher revs.
My rotor housings were PERFECT in the Quasi-Evil Engine. 23k many high-revved miles later, the housing that wasn't demolished was showing some flaking along one outer edge and the chrome along the middle was very "rippled" looking. Essentially, both housings are junk.
mike
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Joined: May 2001
Posts: 12,862
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From: Cleveland, Ohio, USA
yes, i know.
in a post that was lost to the forum crash, i noted that i wouldn't use a housing with lots of chatter marks, since the chrome surface would be compromised and just waiting to start flaking off wholesale.
For what it's worth, the engine spent a lot of time above 6200rpm (the point where the 3mm seals start to chatter). A LOT of time. And then I accidentally exceeded 8500 for a few seconds, which caused a bit of engine blam-age....
i WOULD use housings with minimal flaking, like a dime's or a nickel's thickness at the edge, for a short distance (1/2" or so) and nothing that could catch a fingernail. But the chatter marks worry me.
in a post that was lost to the forum crash, i noted that i wouldn't use a housing with lots of chatter marks, since the chrome surface would be compromised and just waiting to start flaking off wholesale.
For what it's worth, the engine spent a lot of time above 6200rpm (the point where the 3mm seals start to chatter). A LOT of time.
And then I accidentally exceeded 8500 for a few seconds, which caused a bit of engine blam-age....i WOULD use housings with minimal flaking, like a dime's or a nickel's thickness at the edge, for a short distance (1/2" or so) and nothing that could catch a fingernail. But the chatter marks worry me.
Last edited by peejay; Sep 4, 2002 at 05:12 PM.
think of it as a flatspot on a tire. it grows worse exponentially. as the grooves deepen you'll have a greater risk of snapping an apex seal at higher rpm. not to mention the unfinished surface creates greater drag and wear.
Joined: Oct 2001
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From: Fort Branch, Indiana
If you want the motor to run good for a while, lap the side housings, so they are completely true.
The rotor housings will get you about $5 at the scrap yard
The rotor housings will get you about $5 at the scrap yard
Joined: Mar 2001
Posts: 31,835
Likes: 3,232
From: https://www2.mazda.com/en/100th/
Originally posted by peejay
yes, i know.
in a post that was lost to the forum crash, i noted that i wouldn't use a housing with lots of chatter marks, since the chrome surface would be compromised and just waiting to start flaking off wholesale.
For what it's worth, the engine spent a lot of time above 6200rpm (the point where the 3mm seals start to chatter). A LOT of time. And then I accidentally exceeded 8500 for a few seconds, which caused a bit of engine blam-age....
i WOULD use housings with minimal flaking, like a dime's or a nickel's thickness at the edge, for a short distance (1/2" or so) and nothing that could catch a fingernail. But the chatter marks worry me.
yes, i know.
in a post that was lost to the forum crash, i noted that i wouldn't use a housing with lots of chatter marks, since the chrome surface would be compromised and just waiting to start flaking off wholesale.
For what it's worth, the engine spent a lot of time above 6200rpm (the point where the 3mm seals start to chatter). A LOT of time.
And then I accidentally exceeded 8500 for a few seconds, which caused a bit of engine blam-age....i WOULD use housings with minimal flaking, like a dime's or a nickel's thickness at the edge, for a short distance (1/2" or so) and nothing that could catch a fingernail. But the chatter marks worry me.
mike
Old [Sch|F]ool
Joined: May 2001
Posts: 12,862
Likes: 569
From: Cleveland, Ohio, USA
Well, the 2mm seals are a hell of a lot LIGHTER. Consider the rotors to be a car, the rotor housing to be a bumpy road, and the apex seals are unsprung weight.
I don't think chatter marks will "grab" an apex seal. The engine would have lost compression long before that point But I feel that it's a precursor to heavy-duty flaking as pictured above, because the chrome is compressed and stretched and thereby weakened. So I wouldn't use a housing with lots of chatter marks....
I don't think chatter marks will "grab" an apex seal. The engine would have lost compression long before that point
But I feel that it's a precursor to heavy-duty flaking as pictured above, because the chrome is compressed and stretched and thereby weakened. So I wouldn't use a housing with lots of chatter marks....
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