How to figure whether it's an s4 or s5 shortblock?
 

Hello, I have a friend of mine who picked up a rotary shortblock but doesn't know what series it is. Is there any way to find out? I have pictures below
https://cimg3.ibsrv.net/gimg/www.rx7...b8718c5185.jpg
https://cimg4.ibsrv.net/gimg/www.rx7...dc8bb5f153.jpg
https://cimg5.ibsrv.net/gimg/www.rx7...e6bc94d4dc.jpg

Look at the oil filter pedestal
 

There is a casting ridge that is thicker or thinner that runs from the base of oil filter pedestal to the dowel pin. That is usually a dead givaway for the rear iron.

front iron appears to have an oil port immediately next to (13B) stamp on the front housing.

the housings appear to be s5 turbo. Coolant holes on the exh side for the intake mani, and knock sensor ports above the spark plugs.

also your water housing assembly is undeniable s5 with three holes for the thermostat.

has 4 ports for intake…

There are many great threads and posts that highlight the differences. Banzai and other vendors have great pages and pics on their sites as well.

good luck 👍

Edit: to concisely answer you, it appears to be an s5 turbo.

Thank you so much for your reply. Now it's time to look for all the parts to put it together.

And should look at the rotors. Machined compression pockets are s5.

can also measure the compression pockets to verify n/a vs t2 rotors.