View single post by Judson Manning
 Posted: 06-02-2008 08:02 pm
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Judson Manning



Joined: 03-14-2005
Location: Atlanta, Georgia USA
Posts: 406
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 The Elgin article is quite good and does go into some depth regarding practical limitations.  Paragraph 6 under the section Camshafts - "Part 2 choices" is of great interest to a 'stock' JH engine as the example is for a 8.1 c/r where the JH c/r is 8.4.

If we use the 110 timing the stock "C" camshaft with 272^ duration, the intake valve closes at 66^ABDC.  With the 115 timing we're very close to that magic 75^ number the article mentions = very poor low end performance.

As we look at the 907/910/912/920 progression from 1970-1995 we see ever decreasing values of duration (272^ to 252^) and MOP timing (115^ to 104^) with increases in c/r (8.4 to 10.9).  One could only hope the 1995 variant (920) performed better than the original!