>I assumed that the gains in hp (10hp) on Lance's Dak w/ the 1.7
>roller rockers would be a maximum expected since he is running a
>supercharger. No need for a FABM. I also assume that he must have
>a good cam and exhaust to support the blower application. THis
>tells me that if you were to install these 1.7 roller rockers on a
>stock motor you would probably loose hp on the low end and not gain
>any on the high end.
I disagree on this point. The high ratio rockers should add
*something* to an otherwise stock motor. If they don't,
that tells you that the factory rocker ratio is *perfect* for
that cam profile. Hmmm....
A motor that doesn't benefit from having its valves open
longer, open quicker and lifted higher out of the way would
be a strange beast. Again, it seems to point to the motor
being in "perfect configuation" from the factory....
>Also, I was told that higher ratio rockers only increase valve lift
>and do NOT change the cam timing or duration. Mechanically this
>makes sense because you are not physically altering the profile of
>the cam.
Must disagree here also. The high-lift rockers *DO*
change timing and/or duration. What is "duration"?
A measure of the time (in degrees of camshaft rotation)
that the valve is higher than .050 from its seat.
The high-ratio rockers will get you up sooner
and keep you up longer. The duration has been changed!
The profile of the cam is not the only factor when evaluating
cam duration/timing. The ratio of the rocker arms will
definitely affect things.
Of course, people could refute this point by saying
"Scott, I measured my cam's duration by putting
a dial indicator on top of the pushrod and taking
note of how long (in degrees) that the dial indicator
was bigger than .050 inches. Nothing changed
on my cam. The intake valve pushrod was
still higher than .050 for 206 degrees."
Well, that ain't the true, end product. You gotta look at the
distance between the valve and the seat. Will the valve
be off its seat for a longer time period?
You bet!!
I'll see if I can dig up a list of cam books for people to read.
-Scott
"No, Homer, very few cartoons are broadcast live. It's a
terrible strain on the illustrator's wrist."
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