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Update ?? More Cam Theory: Hows about a RDP from OCG?
https://slantsix.org/forum/viewtopic.php?t=51054		 Page 2 of 2
Author:  Joshie225 [ Wed Feb 13, 2013 8:05 am ]
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If you want best torque and power use a 106° LSA with a 225 unless you have a big intake valve that flows well. That's all there is to it. If you want a better idle then shorten the overlap by shortening the duration. If you shorten the overlap by spreading out the LSA you will lose torque over the rest of the power band and you won't get that torque back at any point in the power curve either.

This is good reading: http://www.popularhotrodding.com/tech/0 ... ft_basics/
Author:  akbmotorsports [ Thu Feb 14, 2013 1:56 pm ]
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Quote:
unless you have a big intake valve that flows well
joshua, if you DO have a good flowing valve and head (in my case the engbldr valves radius ground, if you consider those big) would you use a wider spread?

thanks, andy.
Author:  Joshie225 [ Thu Feb 14, 2013 2:07 pm ]
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With a stock intake valve in a 225 the optimum LSA is 105°. With a 1.78" valve its 108°. A 1.70" valve is probably 106-107°. The article has the simple formula. I'd do the math for you, but its a pain switching back and forth with the phone browser.
Author:  akbmotorsports [ Thu Feb 14, 2013 2:23 pm ]
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thanks joshua, did the math yesterday and i got 23.13 which charted to 106-107 like you said. the article focuses on V8s and wasn't sure how closely that relates to the slant.

thanks again, andy.
Author:  Joshie225 [ Thu Feb 14, 2013 3:18 pm ]
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That formula applies to any 2-valve 4-stroke engine. Choose overlap based on intended usage, determine optimum LSA and the duration is derived from there. As slant heads flow relatively well on the exhaust side you reduce the exhaust duration a few degrees and add that to the intake to get the desired split on a dual pattern cam.
Author:  Sprag [ Mon Feb 18, 2013 8:50 am ]
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Joshua, thanks for pointing me to that article, a good read and it lead me to another, slightly more advanced one at HotRod http://www.hotrod.com/techarticles/engi ... ngle_tech/. After this and venturing into "Slant Territory" in general, I find myself looking at engine building completely differently now, more like engine designing I guess you could say. Interesting stuff indeed....some things I would have never thought about had I not decided to stick with the slant.
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