Rocker arm ratio

chrisr

Active Member
#1
I installed a set of 1.1:1 shaft mounted non-roller rockers on my vc460 and was researching an upgrade for my 420 clone. They have the 1.2:1 and 1.3:1 roller rockers like the 1.1:1 non and or roller for the 420 clones but wasn't sure exactly what the net gain would be depending on the ratio installed. Thought this link was a good explanation of the different ratio rockers and wanted to share as well as get your feedback on the larger ratios on the 420 clones.

https://www.jegs.com/s/tech-articles/rocker-arm-ratio.html&title=Rocker+Arm+Ratio+Explained
 

65ShelbyClone

Well-Known Member
#2
The cam and springs play a big part in choosing a rocker ratio. Higher ratios open the valve faster and require it to close faster and demand springs capable of controlling the valve under those conditions. Increasing ratio increases area under the lift curve and even increase duration, but duration (and ultimately power) increases are very minor. Rocker ratio is not an area hiding very much power in the grand scheme of things. A healthy cam and 1.1s will work a lot better than a stock cam with 1.3s.
 
#3
The cam and springs play a big part in choosing a rocker ratio. Higher ratios open the valve faster and require it to close faster and demand springs capable of controlling the valve under those conditions. Increasing ratio increases area under the lift curve and even increase duration, but duration (and ultimately power) increases are very minor. Rocker ratio is not an area hiding very much power in the grand scheme of things. A healthy cam and 1.1s will work a lot better than a stock cam with 1.3s.
 
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