Need 2 or 3 opinions!
 

I traded an ae86 for a 89 s5Gtus,that came with a spare s4 TII motor. Anyways, the fc has bad coolant seal, should i convert it to s4(which ive read its not recommended). Find a low mileage s5 n/a replacement(so i can drive the shit),or sell the s4 TII and use that towards a s5 TII?
Also i picked up a 90 gtu for hundred bucks like six months ago, the car sat for year maybe longer before i got it, because the guy said that one day it would just crank, so him and some friends of his started taking it apart. As far as they got it was just the upper and lower intake manifolds, and just left it. I had a s5 long block from a buddys car that blew the coolant seal, so i used the parts that were needed to assemble it back together. Well I got the engine running, and it started right up, it stays at the write temp, and it doesn't leak anything. I was pretty proud of myself, for assembling the mess back together. Buy today i started the car, and it ran for maybe a min. or less. Than it died, i tried starting it again and now it just cranks!:scratch:
Thanks for your input.

bump...

There's nothing wrong with using the S4 TII short block in your car as long as you make the proper modifications/adaptations. The front cover is different between S4 TII and S5 TII at the metering pump area. You'll need that if you plan to manage the engine with an S5 TII computer, in which case you'll need a harness and all the associated components. Use the search function. There a few more things to consider, but all the information has been posted many times.

As far as your recent build firing up and not restarting, that could be caused by many things. Again, search and ye shall find. Make sure your engine has compression, spark and fuel. If all those things check out, then it might be something else like a sensor, a fuse....etc. Start by ruling things out methodically. There are also links to service manuals here. If you don't own a factory service manual, you need to get one.

Welcome to the RX7 community!

So in order to run the s4 TII motor short block on s5N/A chassis i would need both the lower and upper s5 intake manifolds, s5 afm, s5 ecu, s5 Left hand dirve TII harness or just use N/A Harness in which case i would have to extend two wires? s5 boost sensor, exhaust, etc. Anything else

Thanks for confirming the omp, but ive heard that the s4 is better because of its mechanical function, could the s4 omp be used? Is that mechanical linkage compatable with the s5?(I dont think so, cause the s5 dont have that linkage), if anything ill just get the s5 omp.
BTW... im just using the n/a drivetrain, so i would use the s5 flywheel. The counter weight has to match series of essentric shaft, the s4 counter weight would be used

Yes, that sounds right

The problem is if you're using the S5 emissions control setup, the ecu will look for an S5 metering pump. S4 metering pumps are great and all, but most are quite old and leaky. You'll need to make sure yours is OK or you can recondition it with new seals. Another option is to premix your fuel with 2 stroke oil. Read up on that. If you run an S4 TII engine, just use that series flywheel and you'll be fine. If you're planning on using an aftermarket lightweight flywheel, you'll need a rear counterweight from an automatic. Make sure you order a rear counterweight out of an S4 automatic RX7. You'll find that the N/A drivetrain will protest after a while...the tranny especially. TII trannies tend to be a bit notchier and noisier, but they're designed to take the torque with a bit more margin.

You can simply tie the S5 e-mop off to the side, making sure it's plugged into the wire harness, remove the mop from the S4, install a block off plate and premix. Otherwise you'll need to swap the front covers, per the FSM, while the engine is out, perferably.