I know the basic difference between the two, but someone told me, "instead of changing to the cam, why don't you just go to a larger rocker arm ratio." I believe the reason they told me this, is that I am considering a more mild cam (224/228 .58+ 114 lsa) and that the overall cost of the cam and install is a lot compared to just changing the rocker arms. Also, the larger cam puts me on the border of passing emissions. My question is can a larger rocker arm accomlish the same thing as the above listed cam, and does it effect the emissions the same way a cam does? Thanks in advance for any responses.

 

No, the higher-ratio rocker arms cannot come anywhere near the effect of a cam, and they have issues --- the change in the valvetrain geometry increases the side loading, and can result in faster wear.

The higher-ratio rockers directly affect lift, but have only a marginal effect on duration. To compute the difference in lift, take the following example for 1.85:1 rockers. Divide 1.85 by 1.7, equals 1.088 and change. This means your lift is increasing by 8.8%. If your stock lift is .500", w/ the rockers it will be .544". Not too shabby, I suppose.

However, the increase in duration is miniscule.

HP gains: MAYBE 10 HP, at best. The rockers cost about the same as a cam, and you still have to install them, and you should also change the springs too, and probably the pushrods.

Even a mild cam will give you 25 HP, and a 224/228 could do even better. BTW, whoever told you that is a mild cam is also blowing smoke. The .581" lift is wasted on stock heads, and it's marginal whether it would be able to pass emissions.

There is NO comparison.

 

Tony,

I installed Crane's 1.82:1 aluminum roller rocker arms in my Z06 this past April. At the same time, I also installed their pushrods, guide plates, studs, double valve springs, and Titanium retainers. This increased my lift at the valve from .551 inches to .590 inches. Their is no change in duration. I have had this package on a Dynojet chassis at a steady 6,800 rpms without any valve float.

At the same time I installed the rockers, etc., I also installed a set of L.G. Motorsports Long-Tube Pro headers, with the 3 inch X-pipe, and Random Technologies metal-matrix catalysts.

Together they increased my rear-wheel horsepower from 355 to 400.

In talking to Lou at L.G. Motorsports, he states that his headers should be worth an honest 20 to 25 horsepower in my car. That leaves a 20 to 25 horsepower increase from the rocker arms. My car is much more responsive than it was before, without any degradation in idle quality. It also passes emissions. It took me about 4 hours to do the change in valve train components in my two-car garage, using hand tools, a compressor, and a valve spring compression tool from Vinci Hi-performance.

Good luck with your decision. :seeya





[Modified by Pumba, 6:56 PM 5/24/2004]

 

I am not sure if a 224/228 .58+ 114 cam would pass emissions or not but a 224/224 581 114 cam, like I have, will. While ported heads would make the most of .581 lift, it is not wasted on stock heads. The faster ramp rate of the .581 means that at .200 lift, the 224 .581 lobe will have a duration of 146 degrees compared to 142 degrees with a 224 .568 lobe. In other words the stock heads will reap the benefit of the increased mid-lift numbers.

While high lift rocker arms are less than a cam, I think if you look at it from a horsepower per dollar view then the cam looks pretty cheap.

Since you are only a few miles from Andy at A&A in Ventura, you should talk to him. Call him anytime for product info: 805- 658 -8299 (shop) 805- 479- 5885 (cell).