JAMMNN

I have what I believe is a complete 1987 motor with low miles. I bought a car with no block just all the parts to swap onto a new block (I hope all) are there any differences in the blocks that would not allow me to use it with all my hardware from the 1990?

RX-7Impreza

the only thing you can use is the block but i dont see why you would want too. the S5 is rated at 160 rwhp while the s4 is 146. course most of that is due to the VDI intake on the s5, but partially due to the lighweight high comp rotors and the 8700 rpm reve limiter

Justin

MasteRX

You would have to use an aftermarket flywheel for an 89 transmission, but use a rear counterweight from an 86-88. If you just use the 89 flywheel/counterweight the engine will be out of balance. Also the 89 engines use an electrical Oil metering pump, while 87s have a mechanical one. I am not sure if you can swap them and have them work. I guess you could always do premix. Other than that I think it would work. But, like RX-7Imprezza said, you lose a little power due to the lower compression and heavier rotors.

biorotary

i believe all should work ok...with the exception of oil injector sending unit...the pre '89 has is manual and the '89 up is controlled by the ecu..so if you do a swap...you'll have to pay attention to that...you'll have to use the '87 intake a throttle as well unless you want to mod the '89 intake and throttle...but it your call...it's not to hard...just time consuming...

JAMMNN

Are you saying that the 86-88 have a different transmission?

JAMMNN

What would I have to do about the oil pump? and what mods do I need to do to the 90 intake? I would like to know all the issues before I tackle the job.

MasteRX

I think the transmission itself is similar, but there are clutch interchange issues, so I am not sure if an 89 tranny will mate to a 87 flywheel/clutch. I know for sure you would at least have to go with the clutch to match the year of the flywheel you are putting on. You might be able to get away with the stock flywheel and clutch from the 87, but I am not sure. The stock flywheel on an 87 has an integrated counterweight, so you would be good to go if it mates up. There is also a difference in the throwout bearing, but I am not sure what it is.

MasteRX

On the oil metering pump thing, if you can still use your old electric one, you will be good to go with your original intake. But if the electric one doesnt work, then you would have to use an 87 style throttle body which has the part to actuate the control arm on the OMP. Someone here knows whether you can just bolt on the electric pump to the 87 housing, just wait until they chime in...

Another thought is if you cant use the electric OMP on the 87 engine, another option would be to simply swap front covers, then you will still be using the 89 front cover which can handle the electric OMP for sure.

RX-7Impreza

yeah i forgot about the OMP, you cant just bolt on the electric and your ECU will go nuts without it. you have to use the front cover from an 89+ with the electric omp. you also have to use the injectors from the s5 as the s4's are low impedence and the s5's are high.

the flywheels are an exact swap. the tranny's are identical but you must use the front counter and the 86-8 flywheel

Justin

Felix Wankel

The 86-87 S4s are low impedance. The 88s are high. I think the S5s just have different connectors.

Do not mix and match rotating assembly parts. If you are going to put an 87 engine in a 90 car, put the 90 front cover and OMP on, use the 87 front counterweight, flywheel and clutch. All NA trannies use the same input shaft. Clutch size is irrelevant.

RX-7Impreza

i thought that 86-88 are low impedence 89-91 are high impedence or did it switch before the s5

Justin