Can anyone teach me the differences between, Hydraulic, Flat tappet, Roller Etc. cams and how they work differently? Im curious and its new territory for me.....

 

Wow what a large topic. While I think I know this i don't feel qualified to explain it.

Here is a link that may help some. http://www.powerandperformancenews.c...gory_Code=CAMS

The one thing is does not show is a mechanical roller which would be alot like the mecahnical flat tappet in the performance arena.

A few general comments. 385's have canted pushrods. Because of this Hydralic rollers are always a bad idea. The angle becomes to accute and can cause real problems. Mechanical rollers are better but I prefer hydraulic or mechanical.

 

Flat tappet - the bottom of the lifter is flat (imagine that) and rides directly on the cam lobe. The only thing keeping it from total destruction is a thin film of oil. Most flat tappet lifter bores are slighly off-center from the cam lobe to promote lifter rotation. This keeps wear even. Cam lobe angles are limited by the amount of force you can place on the wear surfaces before the oil film no longer protects them.

Roller tappet - the bottom of the lifter has a roller that rides on the cam lobe. The reduction in parasitic power loss due to friction is sginificant (Ford picked up 5 hp in the old 5.0 Mustang GT motors from this change alone). Since mechanical shear and friction are almost nonexistent compared to a flat-tapped design, the cam lobe angle can be much more severe. This opens and closes the valves far faster and much more efficiently than flat-tappet designs can. The downside is that the extreme acceleration of the severe cam lobe angles, combined with the higher valvespring seat pressures needed to keep valve bounce to a minimum, place much greater stresses on valve train components. Parts designed for roller applications tend to be expensive.

Solid - the lifter body is a solid chunk. It's only purpose is to take the rotational cam movement and turn it into linear movement. Usually use in applications where regular valvetrain adjustment is easily accomplished or considered to be secondary to performance.

Hydraulic - the lifter body has an inner plunger that is held in place by a combination spring pressure and a small reservoir of oil inside the lifter. The amount of oil in the reservoir is variable, and the lifters have a certain amount of "leakage" to allow for shifts in valvetrain geometry as engines wear over time. It also means they are more forgiving to misadjusted valvetrain components. You can also buy fast-bleed hydraulic lifters that partially collapse at low RPM and let you use a more aggressive cam profile that you could normally use. However, these lifters tend to be noisy and can be very sensitive to changes in oil viscocity (temp changes or different oil weights can have radical effects on performance).

In order of comprimise to all-out-race

Hydraulic flat tappet - cheap, easy, durable, reliable. Use these if you want the build-it-and-forget-it engine.
Hydraulic roller - not so cheap, but still easy, durable, and reliable. These are the units to use if you want the forgiveness of a hydraulic, but the performance of a roller.
Solid flat tappet - cheap, has to be adjusted often for best performance, durable and reliable. The old stand-by performance choice, but is being quickly outdated by the newer hydraulic roller designs. The only reason to choose a solid is if your RPM limits exceed the hydraulic's capabilities.
Solid roller - If A) your cam lobes are the size of Everest, B) you have the bank account to afford insanely expensive valvetrain parts, and C) you put adjusting valves right up there with winning the lottery, then these are what you want. Most solid roller designs are for RPM ranges far past anything that's even remotely streetable. But, hey, whatever floats your boat....

Brad

 

What those guys said plus a little more.

The major cam companies make offset lifters to ease the pushrod angles. These are pricey, but not like they used to be. There are also a few companies that make roller lifters that are the same height as a flat tappet. These haven't been out long and their durability is unproven.

I can't think of a single good reason to run a solid cam of any kind in a street truck 460. Modern hydraulic valvetrains can get to 6500 rpm with no worries.

 

Wow thanks for the useful information guys, very interesting.

 

The biggest reason for going mechanical over hydraulic is to improve mid range flow because of more agressive ramps. Cam for cam the mechanical will provide more power. And with exotic lifters like Schubecks cam wear is almost gone reducing the need to adjust so often.

Of course you can get into a roller for that cost but I don''t trust a mechanical roller on the street and in hydraulic rollers I'm not aware of and offset lifter available.

 

So what comes stock in most of these older 385 series motors?

Hydraulic flat tappets?

 

Yes...........