Jack,
Do you know what the cfm flow rate was up to .500 lift? It would be
interesting to know the percentage of change.
The test I was mentioning found the same to be true - that lift over
.500 had a diminishing return on h.p. due to flow.
Thanks for your valuable input.
Allen
On Dec 26, 2007, at 7:18 PM, Jack W. Drews wrote:
> Roller rockers are subject to a lot of debate, aren't they? I've not
> seen actual dyno numbers that are meaningful, but I'd like to.
>
> My two cents is based on flow bench readings.
>
> What I have seen is that flow increases with valve lift at an
> expected rate until you get to between .500 and .600 lift. The heads
> I've done maxed out on flow at between those two numbers, with only
> 3 to 4 cfm increase in flow when increasing it above .500 lift. It
> appears that the rest of the intake tract, namely port shape and
> valve size, reach their limits before valve lift becomes limiting.
>
> It's a different story if you compare flow rates of solid vs. roller
> rockers on a stock cam. In that situation, the max lift on a stock
> cam is much lower so roller rockers give more of an advantage.
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