So my friend was over when I was looking at my car, and out of no where he says what the ****? does a double take and says I have S4 irons in my S5 TII. I have known since I bought my car that it had a rebuilt engine in it, it was stamped on the housings. So its S4 irons and S5 housings with unknown rotors.



My question is that is there a difference in port size/shape on the S4 irons as compared to S5's?

The s4 primary ports open 10 degrees earlier, the rear iron around the dowel is weaker but can take the abuse of high horsepower as long there is no pinging otherwise they will crack(S5 and newer blocks have thicker iron casting around the rear iron tubular dowel pin area). I believe the sparkplug locations are different in the S4 housings compared to the S5 but i don't know the specifics.

Yea I have S5 housings, but S4 irons. Is there no difference in port shape or size?

[quote name='spooliNrx7' date='May 4 2005, 01:02 PM']Yea I have S5 housings, but S4 irons. Is there no difference in port shape or size?


[/quote]



s5 has slightly larger ports in the irons, and they are a little stronger too.