Why do these housings look like this?
 

Hello everybody.

Afer a few hours of looking at a few hundred mazda 13b engine housings i have
come to the conclusion i have no idea why these housings have this style 'mazda' font.

I got a 1982 rx-7 about 2 months ago as a parts car and it was complete with a beautiful running engine and all.

I noticed from the first time i set eyes on this car that it had different writing style on
both of the housings.

I'll let the pictures do most of the talking but i would like to know if my speculation is
correct or not.. is this a mazda cosmo engine? 'jap spec' standard with bigger ports or is it just a line of specific year 13b engines?

I can put up many more photos after i transfer them to my computer from my phone so if the photo i provided here isn't detailled enough i'll be happy to add some better ones.

Any information would be great because i am considering selling the engine after i do compression tests on it and i would love to know if it is 'rare' in any way.

Thank you.
From Jozey.

pretty sure they are from a 70's thats old mazda font.

Looks to be an oldschool/early 13b you have there, I've read they are kinda hard to find so depending on condition inside you may have a gem.

Great, that's just the kind of things i want to hear.

The odometer on the rx-7 read only 30,000miles. i'm not sure how genuine those figures would be but my guess is that this car had some work done to it when the previous owner swapped out the gauge cluster for a low-mile one.

It was running really well just before i pulled the engine out of the car and was fitted with a holley carb and racing beat intake, full racing beat street port exhaust, MSD boxes among a few other things.

I've been thinking of buying a REPU, it seems this would be a good engine to suit it.

That engine would be great in a repu but, equally awesome in the fb. Definitely a prime rebuild candidate seeing as it was a strong runner.

the engine is a mutt!

the rotor housings are 74-75.

the rear iron is nitrided with a screw in heater hose, so its like an 81.

center iron is also nitrided, so its 81-85

front iron is painted, so that would make it pre 1981.

How are you able to tell what has been painted and what has been nitrided?

Thanks a lot for the info, though. I had a feeling this would have been a mix/matched engine.
Do you know if there would be any benefits or advantages from using these particular housings and center irons?

I got a compression testing kit this afternoon and screwed the gauge into one of the lower spark plug holes and turned the engine over by hand. The readings came up to only 30 psi, then i read some how-to's on compression testing a rotary, it said that you should warm the engine up before doing the compression test so i'm not sure if that would make such a difference in pressure. It has me a little concerned but hopefully i will find a way to properly test the engine by warming it up before i fit it into a car or sell it.

Any compression test should be done with the engine being spun by the starter, not by hand. You need to get the engine up to around 200 rpm to get proper results. The engine being warm will help a bit with compression numbers but IMO it is a bit of a false number as it wont properly indicate cold starting problems or the beginnings of low compression. I have always done compression tests on a cold engine and recieved results comparable to what many others post. If you dont see results on a cold engine that are within the proper range there could be a problem.

About the only thing you can test a rotary for when it's not installed is to check for proper smooth rotation with plugs out, and for six approximately even-sounding compression events, one from each rotor face, in the course of three revolutions of the shaft. What's known as the ghetto compression test.

If the engine is 'dry' inside (no oil, no fuel) compression will be low anyway, since lubrication assists in seal efficiency.

You can inspect thru the exhaust ports for apex seal scoring and how much carbon buildup may be on the rotors, you can look for signs of leakage from the main seals, you can look in the water pump ports for signs of excess rusting, and you can swab inside the oil drain with a q-tip to look for signs of metal particles which might indicate an oil pump or excess wear problem due to oil starvation, or water emulsion that might mean there's a water seal problem.

You can use a dial indicator to check e-shaft end play against spec.

If you have the tools for it, you can stand the engine vertically front-up and remove the front main pulley to inspect for seal lip wear, but you have to be very careful you don't disturb the front bearing stack. If you go that far, you could also drop the oil pan and remove the front cover (at the cost of a couple gaskets & o-rings) to examine the oil pump, chain and condition of the front drive parts, and check the freeze plugs for signs of leakage. With the pan off you can check the pickup screen to see if anything abnormal's been sucked up. Changing the front main seal would be a good idea just on principle if you go that far, as it's near impossible to do once the engine's installed.

You can also, with proper tools, pull the flywheel & check the rear main seal & the tension bolt seals & freeze plugs for signs of leakage, & examine the flywheel sealing surface for seal lip wear.

To check more than that, you'd have to do a full tear down and rebuild.

well you can see that the front iron is painted black, and the center and rear one aren't, which is odd.

the 1970-1978 (up to the start of Rx7 production) engines had plain cast iron side housings, with a coat of black paint on the outside.

the 1978 (Rx7 on), engines all had nitrided irons, the nitride coat is grey.

so it would appear that someone used a front iron from, presumably the 74-75 engine, and the center and rear irons from 81 engine.

granted, i'm only looking at a picture, so its not 100%...

I will try to post up some more, better quality photos soon.

At my work, they are thinking of building an engine test cell, so that would be great if i could use that when it's finished in a few weeks.
i'll do as you suggest, divindriver, and try to check those parts for wear and make sure they're within tolerance.

I dig them whatever they are. :D

I've got the same MAZDA font on my 13B and pretty sure it's out of an RX4 or RX5.

http://i4.photobucket.com/albums/y12...5/IMAG0179.jpg
http://i4.photobucket.com/albums/y12...5/IMAG0182.jpg

Off-topic; you RHD folks sure have a lot simpler routing for your air conditioner hoses... here in LHD land they literally route all the way around the engine compartment.

Yeah, but think about the horrors of working on the exhaust and carb and steerage in that tight little bundle.

It's actually not too bad working on the other side. I swapped the steering box out a couple of weekends ago and the only thing that was in the way was a coolant line going to the beehive oil cooler. There's plenty of room to drop the exhaust manifold off as well.

Yeah that looks nice,
i did what i should have done a while ago, i went to wikipedia and it says that these style housings were used in the following cars:
Mazda cosmo AP
Mazda Rotary PickUp
Mazda RoadPacer
Mazda Rx-4
Mazda Rx-5

I had never heard of the Mazda RoadPacer before so i clicked the link and was surprised to find out that Mazda imported about 1000 Holden Hj's and Hx series premier's and replaced their red series engines with 13b rotaries.
They are the only GM manufactured production car to ever be sold with a rotary and most of them were bought by government departments and were later crushed, so they're a rare car these days.

As for the Mazda cosmo AP(anti-pollution) was sold with 12a and 13b engines.
According to wikipedia, it was sold internationally as the rx-5 and in Japan it was sold as a Cosmo AP. But i think it also was called a cosmo in America and carried the 'Anti-Pollution' name for emissions purposes or something..