>I give up. :^( :^(
>I'll just go sit in the corner with this wierd round
>thing I call a "globe" while you guys play with your
>maps of the flat world.
>- -Scott :^(
No no no...don't give up yet...this is fun. 8^)
Ok old man...I'll admit you've pounded one point into my head....the
duration at .050" *will* change (it's *so* slight tho that it really
wouldn't affect anything). The problem here is a matter of defining
"duration". Klaus had it right in that the .050" number is simply a common
lift number for comparison purposes. The *true* duration of the cam is the
degrees of crankshaft rotation from the instant the cam leaves the seat to
the time it returns.
For example..a little different situation....two cams. One for hydraulic
flat tappet lifters and the other for hydraulic roller lifter. Let's say
they have the same duration at .006" of 280 degrees. Both using 1.6
rockers. Most likely the duration at .050" will be different on due to the
more aggressive ramping profiles roller cams use but the *true* duration is
the same.
So....we're both right then, eh? 8^)
In other words......yes.....the duration over the entire profile of the cam
will change slighty by switching the ratio of your rocker arms but not
enough to see it affect the engine the way a grind with a different
duration would.
While we're talkin' about cams....I ran that Comp Cams grind thru my
Desktop Dyno last night for kicks. The plot can be seen at
http://www.geocities.com/MotorCity/Downs/7877/cam.jpg . The solid lines
represent a slighty tweaked 5.2L (muffler, ported/polished throttle body).
The torque figure seems a bit on the high side but this software also
assumes testing on an engine dyno.
The dashed line represents the power levels with simply the cam change. Of
all the profiles I've plugged into this (Magnum R/T, Crower's regrind,
another Comp profile someone gave me, and the 380 crate motor grind) this
one by far is the best I've seen for a street driven truck. It beats the
R/T, brings peak power in sooner than the Crower, and has way more low end
torque than the 380 crate grind. The Magnum R/T grind fell somewhere
inbetween these two graphs.
*** 97 RPM Dakota - 14.98 @ 91.76 *** http://surf.to/real-per4mance ***
sean meldrum
Email @ Home: spm@c3net.net
Email @ Work: sean_meldrum@ittauto.com
Truck mods: http://www.geocities.com/MotorCity Downs/7875/signature.txt
This archive was generated by hypermail 2b29 : Fri Jun 20 2003 - 12:08:49 EDT
