Intake valve length - Explanation needed

[dtedler]

I'm building up a set of X heads for my 340 and have found that a few manufacturers of valves have different lengths (.100 inch longer) over the stock valve length. I am wondering how the additional length in compensated for during the installation? Are spacers to be added under the spring to compensate for the length? Why make longer valves? Any help in this matter will be greatly appreciated. Thanks

[jelsr]

The longer valves are for cams that are really big (liftwise), without cutting the top of the valve guide down too much. Different rockers or spacers are usually required as are longer springs, etc. In other words, there is simply not enough room for a .650 to .750 lift cam without them.