On Tue, 23 Dec 2003, Greg Dito wrote:
> Although I've not seen any comments to this effect, I wonder just what
> rocker ratio is really necessary to maximize power from a stock motor.
> While the logic of "more is better" is often applied I would think
> that at some point much more stress and wear is placed on the
> valvetrain with diminishing return on power.
The real answer to this quandry lies in the ability of the head to "flow".
What your need to do is get your head on a flow bench and measure the
flow. A typical flow measurement will measure flow at various steps of
valve opening. At some point, there will be no more flow gained by opening
the valve more. You then use this number as the target max valve lift.
There literally is no benefit from opening the valve any more than that.
>From all the numbers that I've seen (and this is by no means an exhaustive
sample), the magic number appears to be between .430 and .450 total lift
at the valve.
Note: the flow bench guys will usually give you numbers up to .500 lift
(more if you have the right valves).
If you think you need more than .450 lift, then you really need to get the
head flowed to get any benefit.
Note: there is a disproportionate return in HP gained to money spent on
the flow bench. Getting rid of the inefficiencies has the biggest bang,
but getting into fine details will be getting you the last couple of HP,
not huge gains.
Also a point of information, the advertised JS roller ratio was 1.75:1.
As far as the original question, there are many sources for roller rockers
including Goodparts, APT, TS Imported Automotive, Cambridge Motorsports,
Racetorations, etc.
> Greg Dito
regards,
rml
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