Two RX-7 Motors (What are the Differences, Please)?
 

I've got an 85 FB that cranks and sounds like its trying to turnover (used the MMO trick already).
It didn't seem to sound or start any different after the MMO treatment. A 'piston' mechanic said
the compression was 12 (I'm not sure which rotor he meant). Told me to find rotary mechanic.

ANYONE KNOW A ROTARY MECHANIC NEAR SACRAMENTO!

To me it sounds like there's NOT enough "umph" to start it - Not that that is the case, but that is what it
sounds like. I metered the battery, its fine. I can only guess on the condition of the starter starter, but it
sounds like it up to the task.

I have a video of the start attempt but this site won't accept mp4 (Android) video.

The 85 FB has the better interior. At this point, with a part swap, the 84 is the
better 'body' vehicle.

On the 84 FB. I towed it home from the sale. I drove it to the mechanic, about four miles. Ran hot but made it.
Mechanic did not report any issues with the coolant system other than it should be flushed.

Mechanic reported no other 'major' mechanical issue; struts, suspension, clutch, stuff life that.

Drove it home; ran hot, then hotter. Got it in front of the house, turned it off - and 'POW', overflow tank top pops,
and its "Old Faithful' right there on the curb.

Did a coolant test with a rental kit from the auto-parts store. Pressured it to about 15 psi. Over five minutes it fell to
about 8 psi and stayed there; pressurizing again yielded the same results.

After the fact I was asked if I'd removed a plug and listened for air leakage. I had not. This morning I got out my air
compressor, with a cold engine, I pressurized the system - through the coolant overflow tank tube - to 20 psi.

I could hear a kind of 'crackling', like light frying; or, like something was "under pressure and seeping by".

An air leak, not a fluid leak? The system was definitely losing pressure.

However, there WAS NO fluid, that I could see, in the engine compartment or on the ground under the vehicle. I then
pulled the lower plug and pressurized the system again. I was not able to detect by listening directly over the plug port
whether air was escaping through the port, or whether the sound I was hearing was associated.

It did seem to me that that sound was coming from somewhere in and around the water pump, or at least the passenger side
of the engine compartment.

I've provided pics of both and both engines. If anyone can guide me regarding any of the above, that would be great.
Also, if anyone can tell me any differences - based on the two photos - between the two engines, that would be great, too.


https://cimg3.ibsrv.net/gimg/www.rx7...8be5ba6c6d.jpg
85 FB


https://cimg2.ibsrv.net/gimg/www.rx7...7ba78d1087.jpg
84 FB Engine


https://cimg4.ibsrv.net/gimg/www.rx7...8b5981bd94.jpg
85 FB


https://cimg6.ibsrv.net/gimg/www.rx7...88d49bac44.jpg
85 FB Engine

Did you replace the t-stat yet? Try that and see if it still over heats.

Because these cars will require a bunch of maintenance and repair, unless you have a bunch of money, it's time to get your hands dirty and start wrenching.

I am in it for the long haul.

I bought two on purpose!

The situation looks. as I'd hoped - at a minimum -
- one good body
- one good engine
- figure the rest out
- DIY as much as possible

I'm looking for input and guidance from the forum. Took it to the 'piston' mechanic because no one could recommend a rotary in the area, and I wanted a professional opinion if some sort.

I bought a TS a few weeks ago. I was going to install it. when another forum voice recommended the coolant pressure test first. Again, I'm here to learn.

I will work on changing the TS.

Thank you for your support.

upload it to youtube then link to that video here.

There are a couple of ways a bad internal water seal can present itself One is on the exhaust side. The systems you've experienced with the exhaust gas pressurizing the cooling system is one. We don't this is what happened to yours. The is generally accompanied by steam/water out the exhaust. Running the pressure test one would think that water would find it's way into the exhaust chamber of the rotor. We don't know if that has happened. You can turn the engine over by hand with the plugs out and see if there is coolant/water.

This is all looking at the worse case. We're hoping for a bad t-stat. So far the symptoms are not definitive.

Mike Haag at Haag performance is the Rotary guy for Sacramento.

Both engines are the stock 12A's with stock carbs and intakes, stock ignition and emissions. I can't see the air pump on the red one but it might just be the picture angle (or it may be removed). Silve car still has it. Both cars were mechanically the same when they left the Dealer (engine-wise).

Are there any give aways on the car that indicate whether its 1.1 or 1.3?

yeah look on the rotor housing right above the word mazda. cast into them it will say 12A. that's the 1.1.

and i think in the VIN after the number 33 will be a 1 for 12a. the gsl-se will have the number 2.

https://cimg9.ibsrv.net/gimg/www.rx7...303d6f9f4b.jpg
https://cimg0.ibsrv.net/gimg/www.rx7...b4d4617d58.jpg
Like rxtasy3 said, it's stamped on the top driver's side. But most guys that are talking to you here can plainly see it's a 12a. The 13B that came in the GSL-SE didn't have the carb and blue air cleaner. It had a black plastic air box (like most modern cars) and a totally different intake manifold that wrapped up and had a shoe box -sized plenum right on top. If they are stock it's easy to tell which it is, and yours is a stock 12a. Here's a stock 13b...
https://cimg9.ibsrv.net/gimg/www.rx7...38b787db53.jpg
https://cimg0.ibsrv.net/gimg/www.rx7...1b25babe4.jpeg
the 13b is 20mm longer than the 12a and manifolds cannot swap between them. So it isn't possible to put the 12a's intake onto a GSL-SE's 13b engine. Not that anyone would want to. Long story short, both of your cars have 12a motors and look stock and (99%) original. The only difference between them is the red one has an aftermarket in-line fuel filter just before the carb, and might have the air pump removed (a picture of the right side of engine would clear that up).