Re: Cubic Inch Change - Is it worth it? Opinions Please
[Re: JACK1440]
#2457257
02/25/18 12:57 PM
02/25/18 12:57 PM
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Joined: Jan 2005
Posts: 4,243 Charlotte, North Carolina
sgcuda
master
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master
Joined: Jan 2005
Posts: 4,243
Charlotte, North Carolina
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Everything else being the same, the larger cube engine would make the same power at a lower rpm point, so you wouldn't have to rev it as high. But with a bigger cylinder head, the game changes a little. Max flow on the -1's isn't relevant if you are still using the old cam that doesn't come anywhere near that amount of lift. You need to check the lift points within your cam lift. I don't really think there would be a drastic difference in engine operation with only a 15 inch increase in displacement, anyway. The bigger heads will be the game changer for you.
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Re: Cubic Inch Change - Is it worth it? Opinions Please
[Re: JACK1440]
#2457429
02/25/18 06:51 PM
02/25/18 06:51 PM
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Joined: Oct 2007
Posts: 4,206 New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,206
New York
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The 2.7% displacement change is less important than the curve of cylinder pressure & vacuum per degree of rotation, which varies with rod ratio. The smaller "n" ratio from longer stroke is slightly more tolerant of nitrous and mistakes in ignition timing, also captures more volume at the same IVC point which makes it more tolerant of cams with late closing. OTOH it frequently needs more OL and/or tighter LSA (if the combo is well developed now). Personally I favor more stroke to lower the RPM, and a longer rod to get the thrust vector back where it was.
Boffin Emeritus
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