Originally posted by ludeboom
VTEC is bad for boost because the extra valve lift affects the intake charge pressure or something, some1 explained it in detail a while back.
~boom
if more lift is bad, then drag racers would be screwed.
VTEC systems lose a bit of oil thru the head due to insufficient sealing of the valve seals. this problem happens when VTEC engages... VTEC motors burn more oil than comparable motors.
more lift is always a good thing if you have a valvetrain that can take the abuse.
the problem is duration. VTEC increases lift AND duration... and extended duration means extended overlap. more overlap causes "boost-thru", as the boost charge is pushed into the head and blown right out the exhaust valves. proper cam timing or properly designed cams can resolve this issue, and in many cases, recovers up to 30hp in well tuned motors.
if lift were the problem, then ANY high lift cam would be bad for a boosted motor, which is not the case.