Cams designed for hyd lifters have a very different profile from a cam meant for mechanical lifters.
Mechanical lifters work better on a hyd cam than the other way around if you set the valve clearance at almost zero but the valve timing can become very different when the cam/lifters are mis matched.
This is all due to a thing called clearance ramps which the mechanical cam has to manage the clearance in the valve train before and after the actual designed valve action.
The performance would likely be worse if hydraulics were used on a mechanical cam.
Just learn the art of adjusting the valves.A valve train in good condition with mechanical lifters at the proper clearances will be almost as quiet as the hydraulic fitted engines and the clearances won't need correction before 10,000 miles, probably longer.
MOST performance and hard working engines are still fitted with mechanical lifters/clearance compensators, for several reasons.
I have always been convinced that mechanical cam/lifters experience less wear than the hyd fitted versions because when the lifter is not on the ramp it exerts NO pressure to contact the cam whereas the hyd version is a small hydraulic cylinder- always trying to extend and wiping or thinning the oil film between it and the cam.
Look at a well used camshaft.The hyd cam will show contact all the way around the lobe area while the mechanical cam will appear untouched in the base circle(off the ramp)area.
This all adds up to shorter cam and lifter life for the set that is more in contact.But the machanical valve train must be maintained at proper clearance or wear/noise will result.NO a noisy valve train is not at all desirable and indicates accelerated wear in progress.
Sorry to be so long winded-- it's just hard to find a stopping place sometimes
