I'm trying to figure out what engine block I have and know that there are gurus in here and in the FB forum. Here's what I've got.

74 RX-2 with retrofitted 13B.
Single Dizzy (74-up) front cover
13B block with the old mazda logo on the intermediate plate (circled "M")
Oil injection ports in the housings
Intake mani coolant ports are cast shut - never machined.
Flywheel inspection plate is missing, but the spare GSL-SE plate I tried to place there is about 1.5-IN too short
No side mounts on the intermediate housing.

Check out the pics and see if you can tell me what I have. I'll pull it soon and paint it, but I don't intend to open the block - it pulls strong as hell, still.

 

Rx4?

 

I really don't know where it came from. At first I thought it was a bastard, w/ new housings and 12A irons, but with the intermediate plate marked, I think it might be an original old 13B.

 

hmmm the first rotor housings to get oil injection fittings was the gslse but the gslse i
believe had a 6 port type iron.
so i would guess its a motor built out of gslse housings and 4 port irons.
matt

 

Okay, but haven't all RX-7 housings also had intake manifold coolant passages machined into them? I'm looking at new oil ports and old coolant passages, unless I'm missing something. I doubt they've been cut and TIG'd....

 

the gslse didnt have water running through the intake

 

Looks like a bitsa to me.

RX-7 1st gen end plates, with possibly 1st Gen US Spec RX-7 13B rotor housings? The rotor housings have me a little baffled I must say though. They have the 2nd Gen oil injection nozzles in them, but I was under the impression that all 2nd Gen 13B's have no water o-ring grooves in them so would not be able to be used with the earlier 1st Gen RX-7 end plates.

The US had some different enignes to what we had here, and we never had a 1st Gen with a 13B from the factory. Although I assume the 1st Gen 13B was injectod not carby? And thus had what was basically a 2nd Gen RX-7 motor.

The cast irons are definitely not 2nd Gen RX-7 becasue they are not a 6-Port variety and don't have the injector pockets in the centre plate.

It's not an RX-4 block.

RX-4's did not have the tall port centre plate nor did they have oil injection nozzles in the rotor housings.

RX-4 also had the big MAZDA cast into to rotor housing, not the small mazda raised lettering.

 

I should have thought of that. Having an old logo on the intermediate plate and new script on the housings means it HAS to be a bastard block. I'm curious where the housings came from, though. What 13B ever had coolant seals grooves, blocked off manifold coolant passages, and oil injection? Did the GSL-SE have oil injection on the housings?

 

No idea.

It's a might confusing.

It's like, I know what it isn't, but I don't know what it is!

 

That was my assumption ****, I've simply never seen a whole motor like thus in the flesh to say 100% for sure that that is how they came from Mazda.

So it sounds like it's 1st Gen end plates with early 6-Port rotor housings as I assumed.

 

The GSLSE did have oil injection in the rotor housing and those housings look like they are from a GSLSE. The irons look like they may be R5 irons, which have the tall ports and come from several cars. Pull the packing out of them and give us another photo. If you pull the tranny off and look at the castings on the back, see if you can see an R5. The early R5s did not have nitrited sides, but the laters did. If you have the later R5 irons then you may have a great engine there.
good luck.

 

SE rotor housings
12A plates (can't see the port runners well enough)


you may also want to PM Jeff20B, he is pretty knowledgable when it comes to stuff like this.

 

Rotor housings appear to be from a JDM Cosmo or Luce made between '81 and '85. More likely the Luce, as most of the Cosmo's had 12A 6-ports or 12A-T.

 

I checked a buddy's GSL-SE, and that's what it is. For the Australian's, it's the 84-85 EFI 6-port... same as a S4 but with smaller runners and no coolant passages to the intake manifold. Thanks for the help, guys.

 

I checked a buddy's GSL-SE, and that's what it is. For the Australian's, it's the 84-85 EFI 6-port... same as a S4 but with smaller runners and no coolant passages to the intake manifold. Thanks for the help, guys.

 

This is the first time I've seen this thread. You've got GSL-SE rotor housings and '76-'78 non-nitrided R5 side plates. At first I thought they were 3B castings, but your mention of R5 in the other thread got me to thinking. I'll go out and take a look at my '76 Cosmo to see if its intermediate matches yours.

 

Double post.

 

I just took a look at my '76 Cosmo's intermediate plate and it has that old school M on the front and a clip on the oil filler tube. I wasn't able to see if it says R5 on the backside since it's in the car and kinda dirty.

 

Well, my oil filler tube isn't original so I can't speak to it, but it sounds like you're the guy that knows about these things. From what I understand it's pretty readily-portable if I ever get to that point. I just need pointers now on how to paint the long block without it looking like ***.

 

Mask the side plates and paint the rotor housings first. Then it's easy to mask the rotor housings to paint the side plates so hopefully no paint will be lifted from the rotor housings when removing the masking tape.

Edit: I posted some pics of a built sandwich paint job around here somewhere...

 

Is it possible to polish the housings in-place, or do you really have to unstack the block to do a good job?

 

if the center plate has a tall runners it most likly is a 76

 

the rotor housins are GSL-SE the castirons are from a REPU if the casting code is 3B if the casting code is R5 than it it from a 74-78 RX-4 or cosmo of the same era.

Dan

 

Well, the car's off to get the body worked, so painting the engine is now at the top of my list. I'd like to update the alternator (easy) and waterpump to something more late-model and lighter. Any idea if an aluminum GSL-SE water pump has the same footprint as the R5 irons I have? Are there any better alternatives? Are the studs that previously held the A/C readily removed? Can I just slip rubber caps over the GSL-SE OMP ports since I'm feeding the OMP to the float bowls? Anything to watch out for there?