[Sean73]

Can someone tell me if the stock 240Z exhaust manifold has square ports or diamond shape ports?

I know the cylinder head is square port (duh!). But I seem to recall seeing the diamond shape exhaust runners on a manifold before.

 

[ITS racer]

square

 

[SleeperZ]

The diamond port is on the ZXT (turbo) manifold.

 

[Sean73]

So there must have been some advantage to using the diamond ports for increased flow. Possibly to straighten out flow in the transition to the circular exhaust runners.

I've also found a couple of junkyard Maxima's (82-83) that had diamond shaped ports on the exhaust manifold, mated to circular ports on the cylinder head. Unfortunately, the Maxima manifolds have shorter runners compared to the Z manifold.