Originally Posted by civicized

The reason given for running the vtec water pumps is that they run slower than the LS pump. That means less chance of cavitation at higher rpms. If the pump cavitates, it isn't moving water.
The LS motors didn't run at such high rpms, so it never ran fast enough to cavitate.
Apparently, Honda discovered this at some point, as it would have been easier and cheaper for them to use the LS part. I have heard that the b17 came with the LS pump.

That said, as rangcrx reports. people run the ls pumps on ls/vtecs and report they work fine.

I had heard the only dif between the ls and vtec oil pumps was the washer on the relief valve for the paypass. Take the washer off an LS pump and you have a vtec pump, so the story goes.
But I got curious and tore down both obd1 pumps once to inspect inside and found the gears were different in size, at least in the two I had, so there appears to be more to it than that.

Starting in 1996, both LS and GSR were using the p72 vtec pump.