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05-09-2008, 10:33 PM
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Hear is an article David did on compression, about 1/2 way down the page it covers this based on fuel, I'm guessing you may gain about 10 psi if you advance the cam 4 degrees.
The Power Squeeze I'm guessing you checked this with all the plugs out and the carb opened, my understanding is that is the proper way.
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Has anything you've done made your life better? 
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05-11-2008, 08:53 AM
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On a SBC 4" bore, 3.25" stroke, 5.7" rod with 11:1 CR you would need to close the intake valve about 12-13 degrees later to drop the cranking compression from 210 psi to 175 psi.
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Stan Weiss / World Wide Enterprises Offering Performance Software Since 1987 http://users.erols.com/srweiss/index.html
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05-11-2008, 09:58 AM
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Quote:
Its a 3.75" stroke 4.030 bore, old cam closed it at 47* @ 50 new cam closes at 70 @ 20, not sure how to compare those.
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05-11-2008, 10:08 AM
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Are these solid or hyd lifter cams?
__________________
Stan Weiss / World Wide Enterprises Offering Performance Software Since 1987 http://users.erols.com/srweiss/index.html
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05-11-2008, 11:45 AM
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What is your CR?
My calculations use what I call "Lash Duration". If you take the intake valve lash divided by intake rocker arm ratio you have the intake cam lift to check timing events. ex. 0.018" intake valve lash / 1.5:1 rocker arm ratio = 0.012" intake cam lift.
__________________
Stan Weiss / World Wide Enterprises Offering Performance Software Since 1987 http://users.erols.com/srweiss/index.html
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05-11-2008, 01:37 PM
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If I pick an IVC which gives 210 psi cranking pressure with 4.03" bore, 3.75" stroke, 5.7" rod, and 11.29:1 CR. If I than add 9 degrees to IVC I get 184 PSI. The 9 degrees comes from (106 - 99 =) 7 + ((259-255) / 2 =) 2. What else is different between the two cams?
__________________
Stan Weiss / World Wide Enterprises Offering Performance Software Since 1987 http://users.erols.com/srweiss/index.html
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05-11-2008, 01:45 PM
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Remember a raise in Barometric Pressure will raise your cranking pressure and a decrease in Barometric Pressure will lower your cranking pressure.
About 2 inches of Mercury will change the pressure by about 12 psi.
__________________
Stan Weiss / World Wide Enterprises Offering Performance Software Since 1987 http://users.erols.com/srweiss/index.html
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