I have an 89 tII...
I found a killer deal on a s4 motor with ECU and would like to run it while I rebuild my s5.
Has any body done this? Is this resonably doable?
What kind of mods will I have to make to make this work?
Any help would be appreciated.

 

Installing a S4 engine in an S5 is not "resonably doable". However, you can strip the S4 engine down to the shortblock and then install your S5 manifolds, electrics, sensors, harnesses, etc. and have it run decently.

 

Don't forget to swap the front cover and flywheels if you do decide to use the S4 short block alone.

 

OK...
Thanks guys that helps alot.
I hate to do it...but I don't wanna live without being able to drive it anymore.

 

okay, so I inherited this project where a guy put a brand new Mazda S5 motor in a '88 Turbo 2 car which as you all prolly know came with a S4 motor. Everything is bolted up and... with the exception of the oil feed line. she's ready to fire-up....BUTTTT... the electronics are different. I'm told there are guages that won't work.and on and on???? any suggestions? I hate to sell the car as is. There's tons of upgrades and I'd love to see the car on the streets. I'm in Western AZ, maybe a shop or tech in southern Cali ?? Everybody says I should drop a small block in it but That's a major cop out .. Rotary rules!!