I've read many times that the stock 3mm apex seals for a 12a should never be taken above 8500rpm, but I've never heard anything like that for the 13b in a gsl-se. How high is it safe to rev a 13b that's still uning the stock apex seals?

 

I suppose, it depends on how many miles are on it. But I still wouldnt take much further than 8500. Even though 8500 RPM is pretty harsh on any street driven Rex. But otherwise get some new Apex seals, and youll be good to go.

One more thing, depending on your mods. Sometimes your peak horsepower is at like 7000RPM. So it is kinda pointless to go futher than 8500. Becasue then your HP goes down.

Thomas Stifter

 

OK....

One big reason not to exceed rev's like that on a stock rotary engine is at 8500 rpm the rotors start moving in ways they shouldn't be, like wobbling into the side housings. 8500rpm is not some conservative redline - that's the point at which bad things *start* to happen!

It isn't just the apex seals lol.

If you want to frequently operate and sustain rev's above 8k, you should have things like hardened stationary gears, 3-window bearings, clearanced rotors with snap rings installed, carbon apex seals, etc.... You should also be sure to have underdrive pulleys so as not to cavitate your water pump.

There are lots of reasons not to rev your stock motor that high. Namely, as mentioned, there's ZERO point in it - you're not making any power up there anyways!! Also, your motor might not be the freshest - obviously very high rpm use will put more stress on it.

My feeling is that in most cases 7-7.5k rpm is plenty for stockport motors, and there's little point in exceeding that.

 

I was just talking about the stock seals, not keeping stock everything else. The reason I asked is because my friend has a gsl-se, but it has low compression, and he will be getting a new engine. I will probably buy his old engine off him for very cheap. I have an '85 GS, my engine is still running very stong, runs GREAT, so I will have all the time I want to build the 13b excatly how I want it. I know there are some ways to port a 6port that will give some nice gains in power, but you have to rev higher to get that power. I will not run carbon seals, since this car is driven all the time, and the carbon seals would wear out way too quickly for me.

What I'm asking is, WITH all the other mods needed(hardened stationary gears, underdrive pulley, clearenced rotors, etc.) how high is it okay to rev if you are using new stock seals. The higher it's okay to run new stock seals, the bigger I port the engine.

-Matt

 

Don't forget about eccentric shaft wobble.

 

E-shaft flex isn't an issue untill 10.5K. At that point is where the inertia of the rotors starts to become problematic.

What has been said about your power being dead flat above 7.5K is very true and the engine is essentially freewheeling at those speeds so its not healthy as it no longer is pulling but just maintaining speed. (not sure how to better explain this) It's best to have an engine under load when at high rpms.

The heavier 3mm seals will cause more wear on the housings at such rotating speeds, but many people run them intentionally in both turbo (lower rpm motors) and n/a (rev too the moon motors) without any noticable decrease in engine life.

Your stock primary ports and intake maifold are whats holding that engine back from making decent power.

 

Sorry for the off topic post.......but where are you at in Minnesota, Jimmy?

 

I thought the 13b engines had 2mm seals, which is what I would use. I know 12a's have 3mm seals, but I thought 6port 13b's had 2mm seals. The reason people with turbo cars run 3mm seals is they are a little more resistant to detonation, or because where the apex seal mounts is a little worn out and a little too loose for a 2mm seal, so they grind it out a little to run 3mm seals.

 

I was asking reputable people here in the 1st gen forum about the early 13b and they are certain that they used the 3mm seals. I have yet to tear into our project engine to confirm either way myself.

You're partially right about the reasoning for using the thicker seals. N/A guys would use them if they were worried about cracking the 2mm seals with large shots of nitrous.

Popular belief has it that the 3mm seals don't seal as well as the narrower 2mm due to the angle the face of the seal rides on the rotor housing.

 

The GSL-SE 13B used 3mm seals, as well as all the 12A's. However, the 86-95 13B's and 13B-REW's used 2mm seals.