So where I stand is I have a 1988 s4 GXL engine soon to die, and another 1989 vert N/A block. What I would like to do is rebuild the s5 block and then pull my s4 engine bolt the s4 parts to the s5 and drop it back in the GXL. My questions is what will fit i.e. water pump housings and brackets and what not and im not planning on having AC or power steering, straight N/A drift car.

 

Im currently putting an s5 block from my old vert into my s4 with all s4 accessories ill let you know today if it works...

 

Yes it will work.

 

yes it will work like bolt for bolt and nut for nut? Or am I gonna have to change ANYTHING at all or is this a pretty much tighten on and go kinda thing.

 

It's not exactly the same, and it won't exactly be plug n' play. For one, I'm fairly certain an S4 water pump housing will not bolt to an S5 front cover. If you swap front covers, you'll be able to get around this and use the mechanical MOP/OMP. The port air openings on S4 and S5 blocks also differ, so if you were to try to attach the S4 manifolds, it would leave a gaping hole that led to the exhaust ports. Keeping the S5 manifolds and fuel rails, then adapting the S4 TB would be the best route. That would also give you the opportunity to take advantage of the VDI intake manifold, which means more power. A simple RPM switch/air pump setup can be used to activate the VDI and 6PI (aux. ports) like the S5 ECU normally would.

S5 manifold conversion for S4s: http://homepage.mac.com/carldavis/intake/mod.html
RPM switch VDI/6PI activation: https://www.rx7club.com/2nd-generation-specific-1986-1992-17/activating-aux-ports-vdi-rpm-switches-907824/

 

I'm almost positive it does. I purchased just an S5 block, no waterpump housing or anything else. Never swapped the covers, I just blocked off the OMP and premixed. All the stuff I had to use was from my S4, so I must have an S4 waterpump housing with the S5 front cover... geez did I lose anyone there, lol.


Basically, here it is in a nutshell. Everything IS basically the same, except for some minor details. The S4 LIM will not fully mate to the S5 block There will be a port in the bottom middle of the block that will extend slightly below the bottom of the LIM. You can remedy this by using JB weld or a similar substance to extend the bottom of the LIM about an inch or so. I have also seen someone weld a piece of bar stock to the bottom.

Actually thats the only thing I did.

You will either have to swap the S4 cover onto the engine or block off the S5's OMP on the S5 cover. Removing the front cover is a dangerous thing as you can drop, and subsequently crush the bearings on the eccentric shaft. I decided not to bother with this and ran premix.

Oops. I didn't fully read RotaryRocket88's post. Using the S5 manifolds is the better way to go, if you are willing to do the work.

 

^ Maybe it's the other way around then: S5 housing won't work on an S4 cover. I know I've read a thread recently where someone was mad that the water pump housing wouldn't work. Still, unless you want to premix, switching covers will be necessary.

 

are the S5 and S4 air pumps interchangeable?

 

i assume so but i don't have my s5 tii engine yet.

 

I just did this in my 87 gxl. Motor was toast, spare was 90 block. EGR ports are different and will cause big exhaust leak if using s4 lower manifold on s5 block. You need an s5 upper and lower manifold and stick with the s4 front cover and water pump.. When you have those, you need to do the "s5 manifold" conversion. I opted to use the s5 vac rack so I can switch to air pump actuated aux ports, not exhaust actuated.

Read into the write ups for the s4->s5 manifold conversion.

 

Might help...

http://www.rotaryresurrection.com/2n...o_s4_swap.html

Nic