First off, this isn't a rant or complaint, just an observation. With the exception of emission controlled vehicles, I have seen a trend where 250/292 enthusiasts tend to limit the intake valve sizes in their engines to the 1.84"-1.94" range. And almost thinking that the later is the absolute largest to go with. I have seen that when most enthusiasts begin a performance build-up with one of these engines, they seemingly compare the mods they will perform, to an engine they are more familiar with, say for instance a 350 Chevy. And think that since a 250 is much smaller in size, they need to make a selection for parts that corresponds by a proportionally smaller amount, usually smaller than what a 350 would use, to get the same or similar results a 350 would see. A comparison of these engines on a cylinder to cylinder basis needs to be seen to show how inaccurate a comparison of this nature really is. A 250 at .060 overbore is only 3/4 of 1 cubic inch smaller per cylinder than a 350 is. Many non-performance,low RPM 350's came from GM with 1.94" intake valves in them, as did many 327 non-performance engines, which is even smaller than a 250 by 2 full cubic inches per cylinder. So it stands to reason, that most mods that will show significant gains in a 350, will also show the same gains in a 250/292, especially in the area of the cylinder heads. With the addition of "lumps" in the 250/292 heads,and modest porting, these heads can even be made to out flow many aftermarket V8 heads and still be very streetable, even when 2.02" or larger intake valves are installed, just as a 350 would have with the same head flow and valve size. A 292 is a whole different story. At .060 overbore, it is cylinder for cylinder, larger than a 400 Small Block Chevy, and a 396 Big Block Chevy, and almost 13% larger than a 350. You definately will choke it down and not see all the potential out of it if you put 1.84" intake valves in it, and still, 1.94" might not be adequate either. I think there is a stigma about big valves being "taboo", and only needed for high RPM, or racing applications. Of course, other mods should be done as well to complement the installation of larger valves, such as better exhaust(headers) and ignition, and carb/intake manifold selection to match the intended use, and camshaft swapping is normally done anyway. You wouldn't put a 1.84" valve in a Dart head for your 350. I think one reason some people are disappointed when they modify these 6's, is because they go the wrong direction when choosing parts, thinking they are making an accurate comparison 250 to a 350, when in fact it is the same basic cubic inch, cylinder for cylinder. They end up being too conservative when there is so much more to be had from these engines. A popular trick before there were good aftermarket affordable valves available for the Windsor Ford engines, was to put SBC valves in the Ford heads. The Chevy valves were longer, so it provided some challenges to get the installed height needed in the Ford heads, but provided an economical alternative for the time to put larger valves in the Ford. So I sure the opposite would be the case for the Ford valve in the Chevy head, but as strokersix pointed out, the availability of aftermarket valves for the Chevy is endless, unless you already have the other valves on hand.
