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Low End Torque

 
Old 05-14-2019, 01:09 PM
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Default Low End Torque

This will be a pretty different thread compared to most. I am kicking around the idea of building an aluminum LS for a direct drive airboat application. Max rpm would be about 3500 rpm.

My thoughts are an L33 or LS2 with around 12.0-12.5 CR with 706 heads, custom ground low end cam, dual plane intake, long tubes, and e85 carb to help with compression. I know 243s have superior flow characteristics, but I thought the added compression and restriction from smaller 706 heads would help with low end torque. Am I wrong?

I know a 4 stroke would be the easiest way to make tons of torque, but Id like to stay away from spending +$2000 on a rotating assembly if at all possible.

Does anyone think you could make 200+ hp and 400-450 ft/lbs at around 3000 rpm with a properly specd cam and some of the mods listed above?

i have also struggled to find any dyno data below 3000 rpms. If anyone has graphs/tables under 3000 Rpm please post/link so I can get a better idea of lower rpm numbers
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Old 05-14-2019, 02:03 PM
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Sounds like the same problem aircraft people are trying to solve

http://www.epi-eng.com/aircraft_engi...te_engines.htm

Expensive displacement unfortunately
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Old 05-14-2019, 03:46 PM
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Originally Posted by Pop N Wood View Post
Sounds like the same problem aircraft people are trying to solve

http://www.epi-eng.com/aircraft_engi...te_engines.htm

Expensive displacement unfortunately
Thanks for the link. At least gave me a better idea of somewhat lower rpm numbers.

Unfortunately, you are probably right. The few direct drives I have heard of on airboats have all been 427s.

The LS2 in stock trim is a little better than I imagined however. You dont think their would be significant gains down low with roughly a 2 point increase in compression and 706s? Especially with a cam and dual plane designed for this specific purpose?

All this is is just theoretical at this point anyways. I was just figuring a 0320 4 cyl lycoming makes roughly 160 hp and 311 ft/lbs at 2700 rpms weighing about 270 lbs and can go just about anywhere you want to with 2 people and a cooler on a properly set up boat.

I think if you can hit over 200hp + 400 ft/lbs at 3000-3500 it would be pretty similar performance wise only weighing less than 100 lbs more
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