Side-by-side View of Valves Comparing the valves side byside, you can see the difference. As you can see from my shitty pictures the Intake Valves are different. Not only are they shorter, but the stems are not as wide. Reason one why VTEC valves will not work in a nonVTEC b series head. Valve Differences Intake valves are 33mm wide (v. 31mm for LS/B20) and are about 3mm shorter than the Intake valves from nonvtec b motors. As mentioned earlier, the stems are smaller in diameter as well. Theres also a difference in the exhuast valves, the two being pretty much the same as the intake. Shorter and smaller diameter stems. Thus, VTEC valves will not work in nonVTEC b series heads. Reason 2, why they wont work. Springs/Retainers The springs and retainers are different as well. Since ITR and GSR's have inner valve springs, the retainers are designed to retain both springs inner/outer. Also, the nonVTEC retainers are wider and a tad thicker since they dont have the second plane for the inner valve springs. Also, not to leave out the fact that the LS springs are taller, since the valve stems are longer. I estimate 3mm, not sure exactly what it is. Retainer Keepers lastly, im sure there are a lot more differences than I was able to point out. The last difference is obvious. the valve stems are smaller in diameter on vtec valves (intake and exhuast), well so are the keepers. a keeper essentially has a rib type thing on it that slids into a groove on the valve steem and thus, locks or KEEPS the retainers in place. These are different. The nonvtec keepers are bigger (just like the springs and valves themselves) than the VTEC keepers. i suck at taking pictures.