Name that 12A mod
 

Let's have a little contest. You need to find the mod, defined as a part that differs from a stock 12A, and explain why it's a good idea or a bad idea.

(All the soft seals were stock Mazda parts).

The challenge is to name the most mods on the 12A.

Answers by the first responder get 1 point for each correct answer, the second responder gets 2 points for each new correct answer, the third gets 3, et cetra.

Most points wins.

Here's the deal. Leknaw69, an OGTA who lives in southern Georgia, dropped this 12A off when he came up to Jefferson to pick up the Ghost.

He said it was a recently rebuilt motor with a spun bearing and a new set of apex seals.

Only the Rotary Gods could come up with something like this.

Here's Carlos picking up the Ghost and dropping off the 12A, which is hanging from my tree lift:

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And sure enough, just like Carlos said, that 12A had a spun front bearing and a new set of apex seals, real nice carbon ones:

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Then it gets interesting. The exhaust ports look kind of weird (the darker housing is a stock unit):

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The intakes are funny too:

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And as I looked around, I realized the guy who built this engine either really knew what he was doing or was really good at using up spare parts.

So, who can get the most mods and tell what they do, good or bad? I've found 10.

mods
 

I see six that I can easily pick from the pictures:
carbon seals
corner seals springs
intake water jackets plugged
exhaust ports (ported)
intake ports ported N polished

Carlos scores a 6 out of 10 for 6 points.

There's still at least 4 more out there, each one worth 2 points to the next responder.

I'm not that familiar with the mods for the 12a housings and irons but I'll give it a shot...
1. 13bt exhaust port inserts
2. large exhaust porting
3. street-ported 4port 13b irons

Nice try Aaron, but there's no 13B stuff in that 12A, which is a good thing.

Carlos already got the large exhaust port, so our second responder sleeping-7 scores a 0.

There are still at least 4 mods left, and the third responder gets 3 points for each correct response.

Well, I tried! lol

race bearing (rotor)?

Can't win if you don't play Aaron, and there's still lots of points out there still unclaimed.

Not sure if that's a stock bearing or a race bearing in the rotor DB, can anybody verify?

I know the rotor bearings were replaced for the recent rebuild, the good one that's left is practically brand new. Carlos, you got anything on this?

I wonder if replacing the rotor bearings had anything to do with the front one getting spun?

1. The weird guy sitting in the engine bay. That's a 12A mod if I ever saw one.
2. painted irons
3. porting styles on your irons vary with none looking exactly the same or like 74 spec, so I'd say someone custom ported those perhaps without a commonly available template. Maybe he took a die grinder and a little luck?

Did I guess all three remaining mods correctly?

lmao, yes

1. the irons are painted red.
2. carbon apex seals
3. FD corner seal springs
4. plugged coolant passage in rotor housings
5. plugged ACV passage in irons
6. exhaust is ported
7. intakes are ported.
8. rotor housings are painted (are we counting this?)
9. engine in white car is not original.
10. you have an engine in your tree?

Nice try J9, I guess we should give you one correct answer for the silver rotor housings, I had the paint job counted as one mod in my original tally, but let's be generous.

Maybe another for the plugged ACV passages, I'll have to figure out what you're talking about before verifying.

But the stuff about the engine in the tree and the guy in the engine bay don't count, Jeff already got the guy in the engine bay and my tree lift doesn't count as a mod.

So you may have scored 2 x 4 = 8 points, depending on the ACV passage, but Jeff still has the lead (see below).

Jeff, you did get one more of the mods, the painted irons (and rotor housings), plus two new ones, the guy in the engine bay and the free style porting.

Nice work and thanks, the more I know about this engine, the better (still don't know about that race bearing in the rotor, though).

That puts you in the lead with 3 x 3 correct answers = 9 points.

But there are still at least 4 more out there and each is worth 5 points, so you haven't won yet.

Here's a hint on one of them:

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Two others are also about the rotors, so those should be easy for anyone whose built a 12A.

The fourth will be very hard to get, even though it's the most obvious.

1. The rotors look very clean. Is this how they looked upon removal? If so, that engine barely ran until it spun a bearing. That's unfortunate.

2. Is that rotor still stuck to the shaft in the picture? Othwerwise it looks like the oil seals are either brand new and hadn't broken in yet, or are seriously old and should have been thrown out long before the rebuild. Again it's a picture and I can't quite tell on my end of the internet. Same probably goes for side seals. The corner seals are stock, which is a no-no with carbon apex seals. You need the solid corners with the square cut slots.

As for the most obvious, it's too obvious for me. I'm not noticing anything other than it has rusty intake runners, which is bad because you don't want rusty runners, or it was just a short block and was missing the parts to make it a "long block" like intake manifold, exhaust manifiold or header, water pump, flywheel etc. Does that count? Did I win anything?

well, since paint counts, then i'll mention the deleted corner seal plugs.

and my spatial thinking may be off, but are the rotors two of the same (2 fronts or 2 rears)?

diabolical1, I don't usually use the little rubber inserts in the corner seals, and I hadn't even thought of it knowing this engine has carbons and was supposed to have had solid corners anyway. So it was an out of mind, thus not within my sight, sort of thing.

As for the asymmetric compression "bathtubs", I hadn't noticed. I'm a 13B guy so even if I had noticed, it still would have been difficult. Heck for all I know, the engine builder put the rotors in wrong. I can't see whether there's an F or R in the pics.

On closer inspection, there is kind of an F that can be seen in the front rotor still stuck to the shaft, and it seems to match the other rotor. So they're both probably fronts.

All wild guesses...but oil squirter mod? Balanced rotating assembly? Hardened stat gears? Scalloped rotors?

That's a stock oil squirter. It has the normal cadmium plating, not the dark plating of a full-flow squirter.

Balanced? Um they're both fronts.

Hardened stat gears? I seriously doubt it.

Scalloped rotors? No. They are very stock and one of them appears to be wrong (front).

Ya...didn't think any were right...but it's all I could guess, lolll. Somebody point out the rest!! Why is this even as fun as it is? lol.

Yeah it is pretty fun. I didn't think I'd get into this thread as much as I did.

Now we wait for Ray to come back and tell us how right or wrong we were.

Sorry for the delay guys, us easterners need to get some sleep once in awhile. I'll take the comments in order.

Jeff, yes everything in the engine was really clean, nothing has been cleaned up for the photos. And yes it probably only ran a short time before spinning the front bearing. And yes the front rotor was fused to the eshaft, it wouldn't budge. I got the rotor off the eshaft by putting a block of wood on the cement and whacking the end of the eshaft down on it really hard to get the rotor moving, combined with a few strategically placed whacks with a hammer.

The oil seals are actually in great shape, very little wear on the cutting edge, and the o rings were new on the rebuild. In fact I'm pretty sure all the side seals, side seal springs, corner seal springs and apex seal springs were all installed new on the rebuild, they are in great shape.

Good call on the corner seals, in fact those corner seals are one of the non-stock items. But you didn't identify what was non-stock about them, so no points for you this time around. However you still lead with 9 points from an earlier post.

(For the purpose of this "mods" contest we are not counting normal wear and tear, like the rusty intake runners or parts to make it a long block, since they didn't come with the engine. We only want the mods that were specific to the short block, created by a mechanic and obvious from the pictures. Remember that for this contest we are defining "mods" as "a part that differs from a stock 12A", realizing one person's mod might be another person's mistake).

DB, you get a correct answer for the deleted corner seal plugs, that's one of the non-stock installation mods. To be stock, the stock corner seals should have had the rubber plugs. Or, as Jeff suggests, the square cut corner seals should have been used for the carbon seals (which I will be sure to do when I rebuild). So you score 5 points on that one, which puts you in third place behind Jeff and Carlos.

The rotors are in fact different, one front and one rear as they should be (look closely and you can see the F and R imprints on them) and they were properly installed, so no points there. But you guys are on the right track on this one.

Still three mods left!

Enfi, your suggestions "oil squirter mod? Balanced rotating assembly? Hardened stat gears? Scalloped rotors" were not on my list of mods that are obvious from the photos, so unless you can show us the photographic evidence that supports your claim, these also join the list of guesses. But nice guesses, I'll look for those details when I do the rebuild.

So folks, there are still at least three mods to go, each obvious from the photos, and each counting for 6 points. One of the mods is completely obvious, but the other two will be hard to get by anyone who hasn't built a 12A.

Get two right and you're in the lead, all three and win the contest.

balanced rotors? Perhaps lightened? Something about the E-shaft is funny to me but I cant figure it out.

My guess would be clearanced rotors......

Or, aftermarket rotor labeling....LOL Looks like custom sharpie work to me.

I did the sharpie mods, so those don't count.

One of the three remaining mods does involve the rotors, and another involves the eshaft.

However the rotors that came in the engine have not been modified, since they match their original specs.

Maybe the engine came out of a pre-'83 car and the rotors were replaced with the lighter '83-'85 units?

FAQ Rotor Weight and Compression

Just a wild guess.

Real close Spannerhead, but no cigar.

i guess i don't really go out of my way to use the corner seal plugs all the time, but i do prefer using them versus not.

yeah, i'm usually pretty good with spatial orientation, but for some reason i couldn't "spin" the rotors in my head last night with confidence, so it was just a hunch and i decided to put it out there. i do see the "F" in the front one, but i don't see the "R" on the other. however, Ray put it to bed already, so i suck. :)

that said, i do have a question. i've never worked with carbons before, so do they usually have one or two springs?