How do roller rockers help to add power? I know it makes the engine work easier but they look like they add a good bit of weight. Is it a give and take thing, get power down low and lose it on the top, or what?



Anybody want to give me some extra rockers for testing purposes, feel free.[img]i/expressions/face-icon-small-happy.gif[/img]

 

Roller rockers decrease parasitic loss due to friction and as airraptor mentioned if you change the ratio you can get more and lift and more Effective duration from your cam.

 

Easier on the valvetrain too.....is it on the way for atv/dirtbikes???

 

Airraptor is right on what a roller cam allows. Let me elaborate a little more though. If you haven't seen an automotive flat tappet and a roller cam and lifter, this might be confusing. If you lay a standard flat tappet (lifter) cam next to a roller cam, you will see a huge difference. This difference is that the flat tappet lobes will be fat at the base and have a rounded lobe. The roller cam lobe will be almost the same thickness at the base as it is at the top. This causes the roller lifter to move up very fast instead of slowly running up the lobe like flat tappets. At high RPMs the valve needs to be opened and shut as fast as possible. Due to the speed of the lifter, roller engine need extremely high valve spring pressures in order to keep the lifter on the lobe. Without the high pressure, the lifter can come up so fast, it literally flyes off the lobe and causes MAJOR valve float. On a flat tappet cam setup with high lift, the lobe actually hits the sharp edge of the lifter cause force to be exerted on the lifter bore causing friction and wear. With the roller lifter, the pressure stays on the round roller and forces the lifter directly upward.

As for roller rockers: On a standard setup, the rocker tip slides back and forth over the valve tip as it actuates the valve. Also, the fulcrum point uses a sliding setup on conventional rockers versus the roller bearings in the roller. Both of these sliding areas cause extreme friction and wear. The roller tipped rocker will roll over the valve tip as the valve moves. You can use higher spring pressures to reduce valve float. Good roller lifters are made of aluminum which reduces the weight of the valve train. Reduced weight decreases friction, wear, and the chance of erractic valve timing. You would be amazed at how shaving a few ounces off of the valves, rockers, lifters, and pushrods increases throttle response, longevity, and overall horsepower.

If I was building a roller rocker for an overhead cam atv engine, I would use a roller on the cam lobe, the fulcrum point, and the tip. I am guessing a 5-10% gain could be acheiveable. Just switching to roller rockers on a auto engine, a 12% gain is average.

Since the rockers really won't affect valve timing, the powerband would be the same as stock with more power across the board.

Because of interuptions, it has taken me 3 hours to type this. I kept losing my train of thought, so I appologize if it seems like a cluster&^%$ of ideas.

 

Great description guys thanks alot.

 

Air- nobody reads these forum boards, so go ahead and tell us who is doing these ideas. Since it is out of thecountry i have a idea who it is. You first[img]i/expressions/face-icon-small-smile.gif[/img]

 

Airraptor, Now that you have our interests peaked you can PM me with the details, please.

 

Hope its ready by FSW, I'd like to see it.[img]i/expressions/face-icon-small-smile.gif[/img]

 

So let me get this straight. The Roller Rockers replace the standard rocker arms? If so would it be possible to make an engine like the CRF450 engine even more effecient with them? Also if Im right a Twin-Cam designed uses no rocker-arms at all, so u woudlnt be able to buy them for engines like the C-dale & YZF450. correct?

 

Kodiak, yes the roller rockers replaces stock. Yes the engine would be more effiecent. Even twin cam engines use rocker arms. I can't think of any engine right off that doesn't (although I am sure someone knows of one). One advantage of using rockers is the ability to gain lift due to a ratio between the distance from the lobe to the fulcrum and the fulcrum and valve tip. One example is the comp 305 magnum cam laying under my shop bench. The actual lobe height is .338 inches. I am using 1.73 ratio rocker arms which gives a valve lift of .585". In order to get the 585 lift without a rocker you would need a HUGE lobe. There would be a lot of binding and wear.