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another easy way is to look at the rear plate, if it doesn't have the water tube it's an old school 13B. The back of the plates will have a stamp on it for example : R5.
how can you tell what year a 13b is? or if it is a t2 4port or old school 4 port? thanks for the help
the rotor housings are a dead giveaway between the old school 13b and those in the rx7. old school housings have the work mazda inside a frame. also the intake bolt pattern will also be different between the old school 13b and the T2.
he's talking about the heater hose connection on the rear housing under the oil filter, my '74 13b has one. in fact, all the rotarys i've seen had them reguardless of year.
Basically, It's complicated. If you've got oil injector ports on the housings, then they're GSL-SE or newer (84 and up). If it's got a press-fit water plug on the rear iron it's a newer block - older ones had threaded fittings with a hex around the base. The shape of your intake ports and the casting on the irons will tell you a lot. Irons are marked as follows:
Front: Plain as day underneath the water pump
Mid: On the back side of the boss where the oil filler neck presses in (you can barely see the casting number as an assembled block
Rear: On the bottom-right corner of the rear face
Tell us how your irons are stamped and if you have oil ports on your housings.
The problem with using the front cover, though, is that people often fit 12A or GSL-SE covers to other blocks so they can use a front mount. Yes, cptpain, you're right about the cover but it'll often send someone off in the wrong direction.
ah yes but don't bet on the oil metering port on the housings i have seen many a 4-port 13b that was built with new gsl-se housings.
Someone else mentioned the Mazda on the rotor housings, while that is somewhat true it opens a can of worms also.
It is really hard to say exactly what year engine you have the down and dirty identifier on rotor housings
74-75 (mazda logo in LARGE script inside box or frame)
76-78 (mazda logo in smaller script same as modern housings no oil metering ports on the housings)
84 an up (all have oil metering ports on the housings, there are other individual differential factors but this is a decent generalization)
Crit is absolutely right on the Irons though get us the codes and we can decipher them. However i would not be surprized to find it is built of several different years as most are now rebuilds of some kind or another.
Here's yet another option: If it's still got a flywheel for manual tranny in place, take a peek at the back of the flywheel. There's a 2 or 3 digit number cast into the back, which indicates the series of the motor. Match up the number with what you see here: http://www.mazdatrix.com/faq/flywheel.htm
This can be done even with the engine in the car, by removing the sheet metal plate from the top of the rear iron, and rotating the engine by hand until the numbers are in view.
No, there are no bolt pattern differences. The only real compatibility problem is the location of the water seals. By now, lots of motors have had front covers or housing/iron combos swapped. There are a lot of bastardized engines out there, and I'm proud to say that mine runs great (SE housings and cover, S4 NA rotating assy, R5 pre-nitride irons). In 86, they moved the coolant seals, changed the intake bolt pattern on the 4-ports (turbo cars) and went to the intermediate iron engine mounts.
Anything pre-85 is interchangable, so long as it's properly balanced with the counterweights. Ditto for 86 and up. Like rotarydude said, get a look at your iron stamping and let us know what your housings look like. If you can get to them, take a pic of your exhaust ports too, as it'll help date the housings. Keep in mind, too, that housings are nearly always rebuilt as pairs, but irons get swapped more often and front covers are a complete wash. If you see one of your iron stampings, it might not match the other two, so tell us what you can.
Like my 13B 4 port for example. I have -SE housings hooked up to plates from somewhere between '74 and '78. On top of that I have a 12A front cover.
Are there bolt pattern differences on the intake between the '74-'75 and the '76-'78?
To answer this question is another one that is kind of difficult. The actual bolt pattern is not different however there are some intake differences. This is on the center plate between the 2 rotor housings. (yes to others out there i know there are size differences on the ports but for this it does not matter) On some center ports (and no i can't quote all of the combinations) there is an exhaust riser right below the intake ports, on others it is not there. ( if memory serves me correct it most has to do with 1976 engines however with all the hybrid combinations it can get crazy) You have to make sure that if your intake manifold does not cover the exhaust riser you get an engine without one. If your manifold will cover the heat riser then it doesn't matter which old school 13b you use.
Like Crit I have a few of these bastard engines my favorite combination is to use 12A housings(cast irons,end plates....) a mix of 81-5 (all this is based on exterior port size as the engines are all ported again on the inside) I prefer the nitrated housings also i have found less wear on most of these and i like saving my coded housings for restorations. I use the GSL-SE style rotor housings however i have been getting them from Atkins Rotary (these housings are not really GSL-SE but a j-spec 84-5 style 13b that is not normally available here in the US he has a stash of really nice ones) Now unlike alot of others on my rotating assembly I have been using 86 and up 13b (which ones is based on the final engine if i am using forced induction or not etc etc) using 86 13b there is no change in the compression ratio but there is a slight weight loss in the rotating mass also there is the difference of 2mm apex seals as compared to 3mm, and as long as i am not boosting beyond 15lbs i have found that the 2mm apex seals are fine for street use.
i hope that this helps in your quest if not just ask away and we will try to help
Sorry to bring up an old thread, but this information is of use to me now. So instead of starting a new thread i'll add to this already informative one.
Here's a recent junkyard find, that surprisingly has a 13B. I own the engine, it is just going to take a couple weeks to get it to my place to get detailed shots. But here are the ones i've taken so far. I'm familiar with 12A's for the most part. This GSL looks to have been a swap. The engine mount is gone, i'm guessing it used the front style similar to the 12A so that must have a 12A front cover, right? Other than that I'll get better pictures and use this thread next time i'm up there to take additional detail shots.
I'm planning to tear this down and use what ever parts I can from this and another 12A I have, plus some new parts, to build a simple low boost slightly ported engine that would be for street use. I have a high strung 12A that I can track if I want. Trying to build something that has a little more low end power in comparison.
Any help in identifying this would be appreciated, thank you.
Old School pre-84 13Bs are 4 port. They do not have oil injectors and they have the old school "Mazda" logo on the housings.
As far as mounting any front cover will work the same, it's the cross mount that's diffrent from a 12A mount because the 13B is longer. If my memory serves me right 13B is 22MM longer.
That is an R5 13B. Came in 1976 + Rx-4, Rx-5, and Repu trucks.
haven't the housings been replaced with newer 13b's though? the stamping of "mazda" doesn't look right for a repu, thought they had the italicized "mazda" stamping
haven't the housings been replaced with newer 13b's though? the stamping of "mazda" doesn't look right for a repu, thought they had the italicized "mazda" stamping
74-75 were the only year for the big letter mazda housing. In 76 these came out.
You are correct about the housings not having the italicized MAZDA in raised letters. Also notice the raised area between 13B and mazDa. This says Automobiles on some j-spec engines, and is a raised area on other j-spec housings such as these. Thus my conclusion is the engine is a j-spec in the vague years from '76 to '78 or so. The rear iron lacks an oil pressure sender and was never drilled & tapped for one. The irons are probably nitrided (very good thing) but the e-shaft might have the stupid full flow oil squirters which are dumb for a street driven car as your oil pressure is painfully low at idle. Like maybe 10psi if you are lucky. To make up for this, Mazda installed a nice 17mm oil pump in these. The exhaust sleeves might have the restrictive dual wall construction which can be take out and corrected if the engine will be torn down for a freshening up, which I do recommend because I think I see an EGR port on the intermediate plate which = NO casting and should be swapped out for a nice Y casting from any US-spec 12A.
To get this to fit an RX-7 you need to swap the oil pan to GSL-SE, and pickup tube from any 1st gen. You will also need an intake manifold for a 4 port 13B which the engine hopefully came with. For the carb, a hogged out Nikki is ideal. The manifold can be drilled and tapped for the Nikki stud pattern.
05-14-06, 11:18 PM
