What's you're opinion... stroke vs. bore
#34
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Joined: Nov 2005
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From: Toronto, Canada
what about aspiration? Does anyone think there could be a difference in need for aspiration? Would the shorter stroke benefit more from a larger volume runner, and the longer stroke benefit more with a slightly smaller runner volume? I'm thinking it would benefit more from the velocity, but the difference is prolly more theoretical than physically realistic.
#36
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From: Toronto, Canada
#37
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Joined: Oct 2007
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From: yorkville,il
i remember reading an article steve schmit wrote a long time ago,it addressed a class that was limited to 400 cu in.he said he went with a larger bore and smaller stroke because it had less shrouding around the valves,he was winning so maybe he was right.that was a long time ago.
#38
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Joined: Jul 2004
Posts: 11,332
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From: chicago
I see alot of big power forced induction engines today running smaller stroke and big bores. Maybe it's a combination of the fact the larger bores help unshroud the valves , along with modern valvetrain technology to allow them to spin the small stroke setup to a higher rpm and more reliably , than possible years ago. Idk.
#39
Guess we should've addressed the race vs. pleasure variable.
RPM is limited in most pleasure cases. In most engines, you're not going to just keep raising the rpm. Typically speaking your going to run around 5200 - 5800 peak. Over that RPM i could understand how that would be an advantage with a 12,000 RPM funny car.
Plus just because your pulling more HP doesn't mean you've got the torque to keep a boat going. Which brings us to size of boat/application questions. And I think most people running large cid engines don't run flat bottom 18 foot race boats. Plus.... look to my left... if I'm the one looking for opinions about bore vs. stroke, i'm talking about a very heavy twin engine baja.
I like the stats above about flow. Originally i was thinking a larger bore would require the same volume in a shorter stroke would require more volume, but if RPM is static, the flow would be the same.. still need 502 cubic inches of air for each rotation.
RPM is limited in most pleasure cases. In most engines, you're not going to just keep raising the rpm. Typically speaking your going to run around 5200 - 5800 peak. Over that RPM i could understand how that would be an advantage with a 12,000 RPM funny car.
Plus just because your pulling more HP doesn't mean you've got the torque to keep a boat going. Which brings us to size of boat/application questions. And I think most people running large cid engines don't run flat bottom 18 foot race boats. Plus.... look to my left... if I'm the one looking for opinions about bore vs. stroke, i'm talking about a very heavy twin engine baja.

I like the stats above about flow. Originally i was thinking a larger bore would require the same volume in a shorter stroke would require more volume, but if RPM is static, the flow would be the same.. still need 502 cubic inches of air for each rotation.


