I've done some searching, but haven't found a definitive answer on some basic mods that SHOULD be done to a stock motor during a rebuild. I have a 6-port 1985 GSL-SE motor with 212,000 on it. It has been disassembled and everything is in acceptable shape for a rebuild except for the rotors. They have too much play at the Apex seal grooves. I have another set that I picked up that are in spec. I am not looking at porting, will not be racing, and don't care about more power. This is for a street car daily driver that I want to leave stock. The housings are good except for a small 1/16" strip of missing chrome at the bottom. The parts that I am looking at would be anything that helps for longevity and reliability - not for more power. The car has the stock exhaust for now including a catalytic converter, but I might consider eliminating the smog stuff just for simplicity sake. Can anyone give me some advice or point to some threads that will help me decide what parts I need to get?

 

there isn't really anything, except FD or Rx8 corner seal springs, they are a better design.

i would consider new rotor housings, the better everything seals in the engine the more power you make, and the longer it'll run

 

Sounds like stock was good enough for 212,000k. Stock rebuild will be good for another 212,000k.

 

At least one can hope

 

There is no way a rebuilt engine no matter how well built and high quality parts will never make the original engine's mileage.

Take a small block Chevy. I've seen them run well over 250,00 miles. Yet, when you rebuild them, they don't last more than 150,000 and that's if you did everything right.

 

If it was my car I would street port the engine while its out even if you don't want the extra power now it will already be done when you want more in the future. I ported one of my gslse's and added the RB duals and actually got better driveability,more power and 2 MPG better than my all stock gslse with a fresh rebuild.

 

You might need someone else to build your engines.

 

LOL, that was good. I've wrenched for over 30 years but I've seen many rebuilt engines that I didn't build last that long.

Think about it. You turn the crank so you have to use oversize bearings, you bore the cylinders so you need oversize pistons, you need the connecting rods rebuilt which is done by milling the mating surfaces so the opening is smaller and then it's bored to the correct shape. The heads are probably as good as the factory if you use good valve seals but stock engines need none of that. You replace the cam bearings and believe me, I've seen people say, install the cam in a way you know scratched the bearings. Once you start your rebuilt engine, you're supposed to break it in the way the cam manufacturer recommend which is something like 2000 RPMS for 20 minutes which people ignore.

I don't know how many pistons aftermarket companies produce them but I'm pretty sure Chevy, for all their faults, knows how to build pistons in the millions and they all fit nicely.

You're also supposed to replace all the rod bolts and the flywheel bolts. I've rarely seen that done except when I've done it and rod bolts stretch which is fine if instead of a torque wrench you measure the bolt stretch but the specs expect it to be a new bolt.

Don't believe me, ask a mechanic.

 

I don't expect to get another 212,000 out of this engine. I don't feel comfortable porting the irons and am looking to keep the costs way down. The engine in the car now is a big question mark, and I will need this one down the road. Should I consider newer rotors? If so, would I need a new counterbalance?

 

if you do change to newer rotors then you need the matching counterweight and flywheel.

the 86-88 rotors are the same compression ratio, 9.4, and are just lighter, 10lbs each instead of 12lbs each.

the 89-91 rotors are 9.7:1, and even lighter. i have done this combo, and if you add up the weights of the rotors and flywheel, this is like a light flywheel on a gsl-se engine, which is nice. response was better under 2000rpm, but other than that it wasn't noticeable. if budget is an issue, i wouldn't bother.

if you want reliable, you should just build the nicest stock engine you can, IE new seals, new rotor housings, flat irons, etc etc

 

I forgot something! Don't forget the muffler bearings, always use stainless ones.

 

ha! you forget some Mazda's actually HAVE muffler bearings

 

Another simple modification you can do is to shim the oil pressure regulator. By doing this, you'll increase the oil pressure in your system, which is a good thing!

That small little 1/16" edge around the housing that's flaked off is only going to get worse over time. I think - above all else that you've said - that is a reason to get new housings. Will the technically work? Sure. Will they continue wearing in that location? Sure. Will it last another 220K, no way. It might help if you can take some nice, clear, well lit, in focus photos of the housings, and we can help determine the condition - and whether there are other things to consider. If you have a bunch of play in the apex seal grooves, it's likely that the seals were "tipped" in the groove and have heavier wear along one edge. When that happens, the seals can chatter across the inside of the rotor housing, causing parallel lines to show up on the rotor housing chrome. Re-using those housings may cause greater wear to your apex seals.

You should ensure that your oil metering setup is operating correctly. I've seen a lot of them get gummed up from leaking, and your oil metering setup is a key to longevity. The rod that goes up to the throttle linkage has some very tiny cotter pins, and they're easy to lose when pulling it apart. Just make sure it's cleaned up, looking good and it's best to replace all your crush washers and o rings anytime you're re-assembling.

Dave

 

And, after replacing the muffler bearings, ensure you top off the blinker fluid.