oldchevy46 is correct, except for one thing...

The GM 292 factory head, along with the 230 and 250 inline 6s, is a 9 port head. There are three intake ports and six exhaust ports. Each intake port is shared between two cylinders. And from a performance standpoint if that weren't bad enough a head bolt boss is cast smack dab in the middle of each intake port.

There has been much research and testing done to improve the inlet flow of the stock cylinder head. Everything from an extreme port and polish and larger valves to removing the head bolt boss altogether and replacing it with lump of material which is either expoxied or bolted in to improve flow.

And with lightweight pistons you can safely take a well built, balanced 292 to 5500 rpms with ease.

-ftyler