Nice one. Also see head porting.

thats pretty ugly

Youd think by then Nissan would have improved the flow angles to help remove gases cleanly out of the chamber without back pressure.

Bear in mind that is the "worst" section you could take through the port, right through the centre of the guide boss. Some carefull attention to this area pays big dividends with exhaust flow.

Keep also in mind that, as wonderfull as these cars & engines are, these were designed & priced for those who couldn't afford a 'real' car, something larger & more expensive.

These were the cheapies of the product line where economy of purchase, economy of operational costs & economy of running costs were regarded much more highly than performance. This is why an obsolete pushrod design was continued in production while other, 'better' models got cammer engines.

That these engines can be made to produce the power outputs that they have repeatedly been shown to produce, & still live, is a testamant to just how good the design really is, unsatisfactory port shape & all.

I've seen the same cross section of a number of other engines from other manufacturers, & by comparison, this one isn't too bad at all.