What are the visual differences between the S4 and S5 rotors?

 

I believe S4 are cast and S5 are milled. Someone correct me if I'm wrong.

 

both rotors are machined from cast iron, but on the S5 the 'dish' in the faces has been machined, while on the S4 the dish is left with the cast surface. There are probably other visible differences but this is the most obvious.

 

Thanks guys. Have a pile of rotors I need to sort through.

 

Ok. Here's the $64k question then. I have a set of rotors that came out of an S5 NA shortblock that I bought 2nd hand from a guy that had it rebuilt by Atkins. It seized the front rotor and main bearings shortly after I bought it BTW. At any rate the rotors out of this motor have the cast combustion chamber so they're obviously not S5 NA rotors. There was talk when I bought the motor that he may have had it built with turbo rotors at the time thinking he may turbo it at some point. I called Atkins. They remembered the guy, said they talked about turbo setups but it was rebuilt to stock specs. Obviously not. So....(finally the question)...how do you tell the difference between an S4 NA rotor and any type of turbo rotor? I'm guessing it might have S4 turbo rotors.

 

Can you weigh them? I show 87-88 turbo 4300 gm. and 89-91 turbo is 4075 gm.

Hope that helps...

Jack

 

I've thought of that as a last resort. But I don't have an accurate scale at my disposal.

 

go to the grocery store and stick them on the scale in the produce section. i doubt anybody will notice