TORQUE / HORSEPOWER
Post Fiend
Joined: Feb 2001
Posts: 6,624
Likes: 8
From: Missouri
TORQUE / HORSEPOWER
Cubic inches do not make horsepower but it does make torque. A similarly equipped 331 and 351 will have about the same HP but the 351 will peak out at a lower rpm and will have more torque. Here is a comparison on desktop dyno for ya. They use the same cam, flow data and compression. The one with more bottom end torque is the 351W. Red is HP green is TQ.
http://www.clubfte.com/users/ratsmoker/331vs351.jpg
http://www.clubfte.com/users/ratsmoker/331vs351.jpg
Posting Guru
Joined: Feb 2002
Posts: 1,712
Likes: 1
From: Atlanta, Georgia, USA
TORQUE / HORSEPOWER
Right on, Ratsmoker. One more thing, they both have a factory 4.002 bore, so with identical bore, the difference that makes the size is the stroke, which is 3.0" for the 302, 3.25" for the 331, and 3.5" for the 351. Look at this as leverage. The longer the stroke the engine has, the more leverage, or mechanical advantage it has to move the crank. It's like using pulleys, if you can lift twice as much, you have to pull the rope twice as far. Hope this helps.
Cadet Second Lieutenant John F. Daly III
South Carolina Corps of Cadets, The Citadel
The TorqueKing
Cadet Second Lieutenant John F. Daly III
South Carolina Corps of Cadets, The Citadel
The TorqueKing
Post Fiend
Joined: Feb 2001
Posts: 6,624
Likes: 8
From: Missouri
TORQUE / HORSEPOWER
You are right TQking. There is a difference in torque output when you are talking about boring vs. stroking but its not as much as everyone thinks. You indeed have a bigger lever with a bigger stroke but with a bigger bore you have a bigger hand pushing down on the lever. Stroking does give a slight advantage to low end torque and total peak torque vs boring. Also with boring to get cubes you will get better flow around the valves since there is less cylinder wall in the way.
Senior User
Joined: Jan 2002
Posts: 322
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From: Gloucester USA
TORQUE / HORSEPOWER
that is one way to look at it. but also remember, as the bore gets bigger, so does the cylinder volume. that is more area that the air/fuel mixture can spread into, and since it still has the same amount of time to spark and burn as a smaller-bored engine, this can result in incomplete fuel burn, which hurts power and torque. there are two sides to every story....
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