cam duration and its relation to your power band

[grumpyvette]

viewtopic.php?f=52&t=82

http://www.dapa.org/jhpages/pontiac-cams-2.htm

http://www.compcams.com/Community/Artic ... 2026144213
on the better 23 degree SMALL BLOCK AFTERMARKET HEADS THERE'S ABOUT 5.5 INCHES OF INTAKE PORT LENGTH ON AVERAGE FROM INTAKE GASKET TO THE BACK OF THE INTAKE VALVE AT THE FAR EDGE
quote
"GENERAL RULES FOR CAM SELECTION

1.

Use a fairly tight lobe separation cam and shift at lower RPM with a heavy vehicle running a high (2 series) rear axle.
2.

If you want a wide RPM range with a decent idle, use a wider lobe separation cam.
3.

Disregarding the adverse effect on idle quality and off idle power, a wider duration cam with it's higher RPM range allows you to run tighter lobe separation cams.
4.

Always try different maximum shift points at the strip to find which produces the best ET with your combination. Tighter lobe cams will generally provide better ETs if shifted earlier, in comparison to wider lobe cams.
5.

Both the duration and lobe separation should match the RPM range you plan to load the engine.
6.

True leakdown lifters (such as Rhoads) extends the power range down to a lower RPM, and allows a higher RPM cam to be used in a driveable vehicle.
7.

If running nitrous, use wider lobe separation cams having additional 10 degrees or more exhaust duration than intake duration.
8.

With radical duration race cams (260+), lobe separation may have to be widened due to the negative effects of increased overlap. "

MORE VERY USEFUL INFO, in the links

http://www.popularhotrodding.com/tech/0 ... index.html

http://www.hotrod.com/techarticles/113_ ... ology.html

http://www.enginebuildermag.com/Article ... teria.aspx

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viewtopic.php?f=52&t=528

viewtopic.php?f=52&t=904

http://books.google.com/books?id=1ypb-B ... q=&f=false

http://69.20.53.62/faq_valvetrain.php

http://www.shenyu-sjz.com/parts/camshaf ... mshaft.htm

http://www3.sympatico.ca/david.crooks/cam.PDF

 

[grumpyvette]

look this is not a guessing game (selecting the correct port size)you select and verify the correct port size and cross sectional area,using know calculations, valve diam. and flow rate for the application, verify clearances in the valve train,and that the cam and valve train are compatible for the intended rpm band and stress levels,
you match the cams intended rpm and power band to the displacement and compression ratio,make sure the valve curtain are exceeds the port cross section slightly , select the cam lift and duration to maximize the port flow,potential, select headers designed to operate in the same power band, select a drive train that keeps the engine in that power band most of the time.

http://www.rbracing-rsr.com/runnertorquecalc.html

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