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Discussion Starter #1 (Edited)
its obvious some of the guys on this site need to understand the differance between static and dynamic compression ratios
you need to seriously understand the differance between STATIC COMPRESSION RATIO AND DYNAMIC COMPRESSION RATIO
let me try and explain, the short version is that the PISTON COMPRESSES NOTHING untill BOTH VALVES ARE CLOSED, that the only compression rato that matter,since its the only comprression ratio the engine ever sees.

let me point out a few things
first look at this chart

http://www.iskycams.com/ART/techinfo/ncrank1.pdf

then lets assume your 383 sbc engine has a static compression ratio of 11:1 but youve installed this cam

http://dab7.cranecams.com/SpecCard/DisplayCatalogCard.asp?PN=114681&B1=Display+Card

looking at the cam specs we see that the effective stroke is not the 3.75" that the static compression ratio is measured from about 2.6 inches from tdc so your true working compression is closer to 8.1:1 NOT 11:1

heres a longer more detailed explanation

http://cochise.uia.net/pkelley2/DynamicCR.html

keep in mind that you can easilly run a stattic compressio of 11:1 with aluminum heads if you keep the cam timing in a range so that the DYNAMIC COMPRESSION is CLOSE TO 8:1
take the time to understand the concept,it VERY IMPORTANT
 

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Since we're on the topic of valve timing, wanna go into the differences between a Miller v.s. Otto cycle motor and why it works? :)
 
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