Broke down the engine to the block and took of the rear housing to check things out. What a pain in the *** stripping that thing down. I can't imagine having to do a stock rebuild with all that crap on there. So I'm not sure what to think of these housings. I did a compression test before I tore it down with the schrader valve removed on a traditional tester. It was turning very slowly. After cleaning the starter/solenoid terminals and removing the belts on the pulleys I got it to turn over maybe at half speed. I was comparing it to the 12a in the car by ear. After taking a video with my phone I was able to see 3 even bounces on both housings. I got 75 psi on the rear and 70 on the front. I still couldn't figure out why the thing was turning over so slowly. I put 5mL of motor oil in each spark plug hole with a syringe. After several rotations it came up to full cranking speed. I ran it for about 1 minute intermittently until I saw no more oil mist coming out. After that I did another check and got 130 on the rear and 120 on the front. Definitely reading wildly high due to the cold temp and all the oil not being burned off. I'm no expert as I've only done 2 rebuilds and that as well over a decade ago. I believe the housings I used back then on a rebuild were in a little better condition. On a plus side the rotor and apex slots looked excellent on the rear rotor. I'm going to tear the rest of it down when my engine stand arrives this weekend. If the other housing looks like this as well would you use them?

 

 

first step to evaluating rotor housings is to measure the thickness of your wallet. If it is over the spec, then replace the housings, if it is under the spec, then re-use.

if that engine had decent compression before, it will have decent compression again. the quirk in the thing is that a complete new engine is the same price as a pair of rotor housings and all the seals, and then you can sell off the old engine parts too.

its like a 3d decision...

 

So I decided to get my housings resurfaced for $125 a piece (no cleaning for reduced rate) by Freelance Motorsports. The process seems to be great but my housings were a little too worn for perfect results. As you can see, the scoring is still present near the plugs. There was slight depth to the grooves before, but now they just appear to be shiny. You can't really feel them. The housings are definitely in better shape than before.

I finally got my hands on a GSL-SE donor car. It runs nicely, but was in an accident. I have pulled the suspension, wheels, driveshaft, e-brake, glass moonroof, and all brake parts.

Is there any benefit to using the SE brake booster, master cylinder, proportioning valve, or clutch master cylinder? I see the clutch MC would need a little milling in order to fit the brake booster. Any other parts that are an upgrade anyone can think of before I get rid of this thing?

 

Please confirm, but I believe the diameter of the booster is different between the SA and the FB. The SA is smaller and the placement of the clutch master would interfere with a FB booster.

 

The SE and all 81-85 brake boosters are much larger in diameter. Regardless of clutch master cylinder used, it would need to have at least an 1/8" of material removed from the the side of it in order to fit the SE booster next to it. It would be nice if the SE brake master cylinder bolted up to the SA booster. I'm making all new brake lines so I'll just have to order both M10x1.0 and M10x1.25 tube nuts as the SA/FB brake fitting pitch is different.

 

i think that is correct

i would do some swapping just so i have all the brake lines compatible. either all M10x1.0 or all M10x1.25

 

That would be nice but I don't think it is a big deal to have different pitch threads at the master cylinder side. I just like the idea of having a complete brake system as it was designed.

In the "competition preparation and service manual" it says you have to relocate the clutch pushrod. I don't see how you would do this without relocating the entire clutch pedal. Since I have an extra clutch MC and new ones are dirt cheap, I'm going to go ahead and machine out a notch from the side of it.

 

I should add that I am running the GSLSE suspension and of course brakes in my 1980. So the brake booster is something I looked very closely at. Including dual diaphragm options from a protege and larger bore master cylinder from a 929, to name some. In the end I decided to stay with a GSLSE master cylinder and porting valve.

 

I just realized I have the option of bolting the SE brake MC right to SA booster. The 4 bolt pattern and the fact the SA flange is mounted horizontally threw me off. You can just mount the SE MC to the bolts that are at 12 and 6 that would hold the proportioning valve bracket on the SA.

You didn't specify what booster you are using? Did you use the '80? I've also read the '80 has a booster that is bigger than the '79 but smaller than the FB cars.

 

SA booster , GSLSE Master.

 

So I have just disassembled my SE differential. I've never rebuilt one before but have read the FSM and some archives. More involved than I thought but seems straightforward. I'm hoping I can get a little help making a decision here. The owner of the parts GSL-SE warned me the LSD was acting like an open differential. He seemed very knowledgeable and this rear has 130k on it, so I'm going to take his word for it. After a visual inspection all parts look good. The discs look fine but must be thinning. I already ordered all the bearings. Just the clutch discs alone will be $500 from Mazdatrix. I read over some other archive threads on the power limits the diffs can handle. Seems the weak points are the axles. I'd rather not go the Ford 8.8 or Toyota 8.0 route, but if possible build this thing to handle a lot of power on street tires

. Possibly Moser axles. I did not see the LSD section mentioned as a point of failure. If I'm going to be spending an additional 500 on clutch discs I'm wondering if there is a more robust option that would be worth putting that money towards instead. OS Giken, Kaaz, Mazda torsen?

 

all of those work. we had an OS Giken in the last race car, and it was $$$$$$$$$ but the car was faster, so it worked... the Torsen is also a good choice and its much cheaper

 

Clutch disks may be thinner, but also the GSL-SE LSD had a different clutch arrangement that didn't provide as much lock. Here's a rusty one I took apart:



There are only 2 disks with inner tabs.

Here's a 12A car LSD that has an even number of disks with inner and outer tabs:



You might be able to have the LSD you want by substituting thicker disks or thrust washers and evening out the clutch disks.

I think someone on here was trying to get Moser to make axles, but I don't remember there being a result. They did for a vendor a while back, but people who tried to order again couldn't get them made for some reason.

 

I like the idea of a torsen for a street car, but can a miata torsen (I take it that's where mazdatrix is selling) take up to 400 whp? Any other torsen options out there?

 

I will contact Moser and update on this thread.

 

I am glad you found a used engine. You could have gotten a hunk of junk for you 4K+ if you had paid for a new engine.

 

Thanks. I actually saw this. I think this has been the aberration. I believe IRP has a large sample size of receiving good engines.

 

I really don't know if this is an aberration or not. There are not too many people who tear apart a brand new engine. If you notice in the video when they tear apart the new replacement they say around 7:10 this engine had the same water but doesn't seem like it was sitting as long. Since they knew the shop was breaking down the engine they may have specifically pulled a newer one. This engine was better but not perfect. At around 8:25 or so you hear him say this is not what they expect from a new engine but they were not going to send it back again and will just work with it.

Not really trying to put any negativity in your thread. I am sub'd and wish you luck on your build.

 

that video is a publicity stunt...

if you want the counterpoint, my local dealership has sold ~2 engines a month for the last 20 years and haven't had any trouble

 

Now back to this being my build thread

Before I start perusing miata forums to see how much the torsens can handle, is the mazdatrix/miata torsen the only option? Any other aftermarket companies that have beefier ones that drop in?