Spook

Can someone help me understand how a steel hydraulic roller cam works in the ZZ4 crate and why it doesnt need to be broken in like your more traditional cams. :confused: :confused: :confused:

I think I get the deal with the roller part being more of a steep lift and the hyrdaulic part have the oil flow help control the craziness. I just dont see why this design wouldnt require some sort of break in? Does it have to do with it not requiring the lifters and whatnot to seat themselves with the cam and obtain the proper running orientation?

Thanks in advance, Hopefully the forum is crapped out so people can actually see this.

Spook
:reddevil

Fevre

In a flat tappet design the flat end of the lifter rides on the cam and wears a pattern in both the cam lobe and lifter bottom, they need to be broken in. In a roller cam the roller just rolls around the lope and wears no pattern so no need to break in.

zwede

A flat tappet cam/lifter uses a pretty clever way to minimize wear. The way the lobe and lifter are designed, the lifter will actually rotate in its bore. This rotation spreads wear and pressures on the lifter. It is accomplished by grinding the lobes with a slight slope, they are higher towards the rear. This also has the effect of pushing the cam to the rear.

A roller cam has lifters with wheels. The wheels roll on the cam lobe. The cam lobe is made of much harder material than a flat-tappet cam. The wheel is hardened steel. As long as the roller bearing is lubricated (and spring pressures are reasonable) they will last almost forever.

With a flat tappet initial break-in is critical, as the rotating lobe/lifter contact patch has to be established. Chevy V8's use splash lubrication to lube the cam lobes. There is not a lot of splash oil at idle. If you start a new motor and idle it, a flat tappet will not have enough oil on the lobes, and the lifters will not start to rotate properly. The lifter then wear in one spot. Once this has happened, it's all over. Nothing will make the lifter start to rotate and it wears down almost immediately.

Spook

Fevre,

Knew you were going to be one of the guys on this action. Whats the actual operational differences of the different cam styles. Do I have it right, or somewhat close for the roller?

Spook
:reddevil

Shark Racer

I think Zwede said it best.

Because of its nature, the hydraulic roller can handle faster ramp rates. (IE, less duration but more lift). With a flat tappet cam, it would almost be like the cam running into a brick wall to have to deal with the sudden ramp. It'd wear down the cam and the lifter very fast.

-Steve

Fevre

:iagree: Zwede gives an excellent explanation, only other thing to add is the roller cam requires a stop/botton/bearing to keep if from moving back and forth.

I always thought it would be wild to create a roller cam that has a pattern that actual changed a little within the lobe and the roller was more of a ball instead of a cylinder. The cam could then actual move a little to change the duration, might use some type of elec motor or something to move the cam back and forth tied to the rpm's. I know there are variable duration engines out now but I am uncertain how they function.

Shark Racer

Dave McClellan has a neater idea-

Electromagnetic lifters that have lift controlled by a computer rather than a camshaft. Not only will your computer calculate AFR, but it will calculate how much lift to give to get you the maximum power ALL THE TIME. :eek:

Fevre

Typical, I am always a step behind. :lol: Guy here at work saw some Ford proto heads tested that had cams with slits in them so when the slit came around it was like the valve opening, wild.

Shark Racer

Fevre- Now that I've gotten home, I did some research.

VTEC works precisely like you just said. As the engine revs up, the cam shifts forward to a different set of lobes designed for high RPM. :) In the 93-96 prelude, the shift was supposed to occur at 5000 rpm.

-Steve

Fevre

Steve

Now if I can just think of it first! :lol:

Chris

cardo0

:lol: Electromagnetic lifters or solenoid-operated valves would have to be as accurate as a camshaft profile. To control valve timing and prevent valve bounce would take very accurate and sensitive solenoids. We ain’t there yet, at least not economically. For the money camshafts and lifters do the best job.
Now ‘bout 15 years ago there was a demo engine (V8) on national news that was running on solenoid operated valves (no cam) and the inventor claimed Detroit would soon follow. Noth’n on the road yet. I’d guess that valve train would fall apart in just days. Bet his engine is in the scrap-yard or at least on a shelf somewhere. Same place I think Split Fire spark plugs belong. :lolg: