gearhead-42

Can those in the know help me identify this motor? I'm tearing into it to replace a blown coolant o-ring and want to know what gaskets I need to look for...


The lettering on the rotor housings is "mazDa Automobiles 13B"
The rear and intermediate irons are stamped "R5"...



Here's a shot of the intake/exhaust ports... pardon the rust



And the plug side... not the best picture, but I think there are what's referred to as "eyebrows" over the plugs?



Not that it affects the innards, but it runs with a Weber 48 IDA and RB long tube headers, with a lightened flywheel. Based on that, any recommendations on the best (read, cheapest) gasket set that will work since I don't need to match carb parts, and won't be using a pan gasket?

There are still crayon/chalk marks on the rear housing behind the flywheel, wonder if those are factory or a rebuilder? The tension bolts are marked with green paint...

Thanks for your help folks!

trochoid

iTrader: (6)

Atkins may still have a 74-78 12B gasket set, not sure if it wil be the cheapest. An SE kit can work, but will come with unneeded gaskets. If you want only internal gaskets, you can buy them individually.

Engine looks to be a 74-78, Jeff20b can tell you much more about it. Post a pic of the logo, cleaned off.

Midwest 7's

iTrader: (4)

its not a 75.
i've never seen that upper reinforcing below the mazda print, like on 12a rotor housings.

Midwest 7's

iTrader: (4)

^^

diabolical1

iTrader: (3)

PM Jeff20B. he knows about all those housing codes R5, Y, etc.

Fred Villamor

Looks like an '85 Gsl-Se motor ... in the 1st pic you can see the 13B on the Housing ... the only 13Bs with distributors were the Gsl-Se I think ...

1badFB

iTrader: (1)

Nice try, but its missing the 5th and 6th port.

steve84GS TII

Since there are signs that it was rebuilt,Im gonna put my money on it being a mutt.

Its obviously not an EFI engine,since there are no aux intake ports,and I assume that there are no injector bungs in the center iron.You can also rule out the TII 4 port 13B,since there is no knock sensor bung in the center iron,or turbo oil feed on the front iron.
What makes me think its not just a plain old 70's 13B,is that it has a rear iron with an oil pressure sender.I could be wrong,but didnt pre-81 rotaries lack an oil pressure gauge/sender.....I guess it could have been drilled/tapped.

My guess would be RX-7 12A irons with SE or 70's rotor housings.....they look like SE rotor housings.

flight_of_pain

^ ive never seen us spec housings that said mazda automobiles, they have the casting boss, but it hasnt been cut to say automobiles on the us motors. so i would have to vote on a frankenmotor. that looks like 12a rear iron to me


isaac

gearhead-42

Frankenmotor... I like it!

It was in the 83 GS when I bought it... So there's a good possibility that the dizzy is from that... but the 83 had the oil cooler under the oil filter, so if the rear is from the original 83 12a it was swapped out when the original owner installed the FMOC...

Keep it comin! I'll get a better photo of the script on the casting tomorrow...

Thanks!
Dan

Atkins Dan

76 to 78 13-B out of a Cosmo or RX4 as thoes motors had the R5 castirons for that vintage {I am thinking pre RX7 for that info} the REPU had 3B castirons..

as for me having all the parts to rebuild it..You bet I do!!!!


the green paint and chalk marks are from the factory....

Dan

Midwest 7's

iTrader: (4)

dans got it right i bet. kind of what i was thinking. 76-7813b.
they're not se housings. se housings dont have the reinforcements i pointed out earlier in the thread.

Atkins Dan

{Fat ego talking now...} you know I am right Midwest as that is why most of you guys like me here on this forum.. {Smile}

Dan

Nismo Convert86

iTrader: (7)

I love the ADD avenger costume you're rocking in your avitar.

But I thought the early 13b's had way bigger intake ports, but I haven't seen too many.

84stock

iTrader: (5)

The early 13b had smaller intake ports and especially smaller exhaust. I saw a pair of housings for a very early 13b that had tiny exhasut ports. If the housings turn out to be good, I would opt to get a set of 12a center & end plates and port them. Just a suggestion......

84stock

iTrader: (5)

Here's a link for you http://home.iprimus.com.au/bluey3/portsPage/ports.htm

Jeff20B

iTrader: (13)

It looks to me like you've got a J-spec '76-'78 engine (with later opening and later closing exhaust ports). It looks like it's been sitting for a while. Hope it's not rusty on the inside.

Do yourself a favor and reach a finger inside the primary ports (intermediate plate). I've got a hunch that those ports are going to be very small. Compare them to the inside port size (timing) of the end plates.

You're better off getting a Y intermediate plate like I did for mine. Find out why in this thread. https://www.rx7club.com/forum/showthread.php?t=591879

drunkclever

.. green paint.. chalk lines.. I can't see them.. i need to have my eyes checked lol

gearhead-42

Nicely illustrated, thanks!


I'll post some snapshots of the housing as requested, and one of the chalk marks (just for kicks)

It's a bit rusty on the outside, but I did have the forethought to coat the innards with a mix of ATF and Marvel Mystery Oil prior to parking it, and the motor turns over smoothly by hand (and I mean hand, not wrench)

gearhead-42

So, you can't edit after 30 minutes huh?

Anyway, this photo shows the script on my rotor housings... I lifted it from jeff20b's thread on fighting reversion... mine are identical.

Midwest 7's

iTrader: (4)

heres the 74-75 13b housing.

gearhead-42

Some snapshots of the green tension bolts and chalkmarks...







Also, obviously no EGR on this housing ...

kenn_chan

those houseing look identical to a 76~78 Luce rotor houseing. if it has no egr, and small ports, chances are its from a Luce. the cosmo of the same years had larger ports. the luce was mazdas luxury roatary powered car at the time, and required less top end with a different torque curve, so they changed the timing on the ports and built it for torque vice rpm.

Or like said before, it could be a frankenmotor that someone made up from parts.

kenn

diabolical1

iTrader: (3)

i've never laid hands on an old J-spec motor, but i can spot enough differences from your pics to agree what Jeff20B in the statement i quoted from his earlier post. it's what i suspected, but i know he knows the subtle differences more than anyone i've come across on this board, so i figured i'd wait for him to chime in and confirm what i was thinking.

one thing is clear, this motor should be disassembled, refurbished and rebuilt with care. it deserves another lease on life.

steve84GS TII

Did any of the Jspec luxury cars of the 70's have an oil pressure gauge on them?
I know my old RX-4 13B didnt have one.....