If you are trying to build a mostly S5 engine with S4 rotor housings, that will work just fine. If you use the S5 front cover, you need to use the S5 front hub and the S5 pulleys for the ignition timing marks to be in the right spot. The location of the plugs in the housings is a non-issue for a mostly stock motor. I'm pretty sure my last motor was using 1 S4 rotor housing and 1 S5 housing.

 

Yeah, that's what I'm trying to do.
Can you use a s5 eccentric shaft with s4 rotors?

 

On S4 the knock sensor is located on the iron, center one IIRC
On S5 the knock sensor is located on the front housing

 

eccentric shaft is the same for all turbo and n/a S4 and S5 cars.

 

Ah Jesus H Christ................five degrees ATDC is five degrees ATDC no matter is you put the sparkplug holes in the tail pipe. Both series four and five are timed at 5 and 20 degrees ATDC.

TDC has squat to do with the location of sparkplug holes.

 

So if I have s4 rotors, housing, and irons but use my s5 hub, shaft, pulley; The timing won't be off enough to cause the car to not run/run bad.

 

Bump.
Trying to find answers before I buy a lot of s4 parts off of someone on the forum.

 

bull fing **** i have proof of this. i built my motor with one s4 an one s5 housing. using a s4 front hub assemblys4 cas gear. I had it tuned off a megasquirt. It doesnt matter at idle but once u start getting higher in rpm the spark will become unbalanced. causing the s4 rotor housing to fire at the right time as the s5 housing will try to spark early at the normal s4. the plugs are up atleast 1/4inch up from s4. I blew out my motor cause if detination at high rpm due to having an UNBLANCED spark. if they are 5 degrees of difference or what ever at 13psi at 7500 10degrees of spark one will be 10 s4 the other wil be 15 s5. to me this matters