Tonywingrove

Would like to boost my HP on my truck and replace the rocker arms.

RLXXI

(2:1) I don't see how replacing the rockers will make any difference if you leave the cams stock.

Get a programmer and custom tunes, 30-40hp increase depending on tune.

River1

With the stock cam duration wouldn't change, but the speed of the rise and fall can be altered with a change in rocker geometry. The effect is the same as changing the geometry of the cam lobes. Although there is no comparison in observable effect, the same thing happens when the pivot point is changed when lifting something with a lever and a pivot wedge. Another example is with smaller or larger tire diameter. Rotation speed doesn't change at the hub, but with a larger diameter the diameter speed is faster and with a smaller tire the diameter speed is slower.

I don't know much about engines anymore but I agree that changing rocker arm geometry would be a lot of work for not enough advantage to justify the work involved. But I admit I make this statement with minimal knowledge about todays engines. I'm just pondering the basic geometry involved because just like the lever example, the pivot point of the rocker would have to be physically changed. Seems changing the pivot point would require a lot of tight tolerance machining on the head and with the parts that would be required. As far as I know you can't change the location of the pushrod or valve stem. Or can you? I'm guessing putting in a hot cam would involve a lot less work and at a better price. As suggested, putting in one of the performance chips would even be a better option considering the work involved. A chip is also an option that isn't as permanent as the other choices. Change the rocker arm geometry and then desiring to revert to stock specs isn't going to be a small matter in time or to your wallet.

Again, I could be wrong but I can't imagine how. If I'm "all wet" about this, would someone take a minute to explain it? Whether admitted or not, I can't be the only one that's got something to learn here.

RLXXI

There are no pushrods in a OHC engine, the roller rockers are sandwiched between the cam and the valve via a small hydraulic tappet.


#2 in the picture would be the rocker in our engines, the cam bolts down directly on top.

River1

Rnlcomp,

I should have realized this. A mistake I won't make again. Thanks.

Being an OHC engine doesn't effect the meaning of rocker arm ratio does it?

RLXXI

No.