There are 4 cam styles - hydraulic , solid & roller
I will explain some of the differences & applications for them. The differences for the most part describes the lifter, which is the part that actually rides on the cam
1] hydraulic - these are the most common & are used in most stock applications for the low cost & unneeded maintainence. The advantage to this design is is that there is a piston inside the lifter which floats on oil & can adjust the valve lash by trapping oil under the piston, this eliminates the need to adjust valve lash by constantly making the adjustment. The down side is at high rpm the lifter can overadjust [pump up] not allowing the valves to close. There are high rev lifters available with better oil control to help prevent pump up & there are Rhodes style lifters available as well which help with long duration cams & will bleed of movement ofthe valve at low rpm improving idle while maintainng high rpm power.
2] solid - these are an older design but they work great. The lifter is just a solid billet that rides on the cam & holds the pushrod, these require adjustable rockers & different pushrods than hydraulic, the lash is adjusted by adjusting the screws on the rockers using feeler guages & has to be done occaisionally probably once / year, race or street , after the initial break in, these are very stable & will work at low rpm or high , the last production engine to use a mech cam was the /6 in the early 80s. The only change in mech cams was the mushroom lifter these have a wider bottom face & were created to try to get lift speed similar to roller cams without rollers & these have to have the lifters installed from the bottom of the block before the cam or crank are installed.
3] rollers - these are the ultimate cam design. the duration can be kept low so the low end power band is maintained but the valve can be opened very quickly with the steep cam lobe angles allowing very high lifts & a much wider power band than other types of cams. The lifter is designed with a roller brg in the bottom of it so that the edge of the lifter cannot dig into the ramp on the camlobe with the extreme angles.Thhey require mechanical pushrods & adj. rocker arms as well for most applications. These will make more power & fuel economy than the other designs also. New production engines have virutually all gone to this design for this reason, but they have created a hybrid by using roller lifters with hydraulic adjustment. There are also new lifters available for roller type cams with rounded bottoms made of increadidbly hard composite to reduce failure of lifters which does happen with roller lifters From Schubeck Racing Engine Components in Vegas. Be warned they are far from cheap though. All Roller cams are made from billets not castings, as hyd & solid are , due to the severe stresses they are subjected too , they also require much higher quality valve springs to survive the heat generated by moving the valves as fast as they do.
4] is the hyd roller cam combining the slef adjusting hyd design with the roller to ride on the cam , Almost all new engines use these . The limitations of the design are that using fast ramp lifts & higher lifts require insreased spring pressures the hyd system in the lifter cannot hold extreme spring pressures so the performance of these cams is limited
The other thing to keep in mind is Mopar big block cams come with either 1 bolt or 3 bolt timing chain mounting on the front of the cam & often when going from a mild cam [1 bolt design] to a performance cam [3bolt design]the chain will have to be changed.
