Whenyou inject NOS ( especialy a big shot) the your MPH is going to increase a lot.
And the resulting engine rpm at the top end. The mechanical lifter camshaft will tolerate a lot more rpm before bad things happen .Like lifters pumping up from valve foat at high rpm.
having both valve held off seat while injecting nos and throw in ignition and you got trouble.
can you say BANG!!!.
Solid lifter cams ( flat tappet or roller rev higher and tolerate momentay valve searged thu the rpm range al lot beetter. Hyd cams do not recover from serge like a solid will. ( the lifters pump up)
When runing NOS you can expect higher engine rpms. Can be very critical depending on how your car is geared. The solid lifter cams work better. More stabe at high rpm more power at high rpm.