Hey everyone, my name is Seth and I own a 91 NA that I bought with a blown motor. I saw Kevin's post in the for sale for a Mazda reman S4 core and im interested in getting this for cheap to get my car running. My question for you guys is has anyone run an S5 with an S4 motor? If so, what do you guys think about the swap? I am wondering how hard the swap of all the stuff off my long block S5 over to the S4 core would be. Can someone shed some light on the build up of the long block? Thanks in advance.

 

ok i have done this swap and its one of the worst swap u can do to a rx. Everything has to change and i mean everything; wiring, resistors, tranny wiring, its just nuts. If you can stay with same year model s4 to s4, s5 to s5, its just not worth the time unless you have a s4 car you can strip or know how to rewire. It was a fun long project for me though hehe

 

Definitely look for a replacement S5 engine, or rebuild the blown one. Not only will it make the install far easier, the S5 engine has many improvements over the S4, and who want's to downgrade?

 

Can you explain the comment about everything having to change? This is just the core, as I would be swapping all my S5 components over to the S4 core. I am only considering this as an option to get the car running until I can afford a nice S5 rebuild. So really, if everything was swapped from my S5 to the S4 core, and all the emissions were removed and blocked off with block off plates from Rotary Ressurection, as well as the EGR and the MOP blocked off because I would run premix anyway, the car would be the same besides the S4 core. I dont see where any wiring would need to be swapped, since all the components going on the S4 core would be my stock S5 components. I mean, personally I dont see any extra work involved, since if I had an S5 rebuild, I would be tearing the long block down to remove 5th/6th port sleeves (please dont let this start a debate on why or why not to remove) and removing all the vacuum spiders and such. If so, I would need all the intake mani. gaskets as well as some new vacuum line and block off plates for the ports, correct? Anything else I would need to replace while the intake is off the car? Thanks for the help guys.

 

no you can definately bolt up all the s5 stuff to the s4 block. You need to change the front cover to use the s5 omp, but if you're blocking it off it doesnt matter too much. The intake is a pain in the *** to get all matched up because they have some differences. There's a few writeups about that. It's do-able. It's in my car.