Bore VS Stroke
Thread Starter
Burning Brakes
Joined: Oct 2000
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From: My Own Private Idaho
Bore VS Stroke
If two engines had the same displacement, but one had more stroke, and the other more bore, would torque be equal? In other words, is torque dependent on bore or stroke? I ask as I see the big Harleys and their great torque compared to my Honda 750, but WHY do they have torque. Simply due to the SIZE, regardless of the stroke/bore relationship?
thx
thx
Safety Car
Joined: Jun 1999
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From: Austin, Singapore, Kuala Lumpur, Houston, Dallas, Hong Kong, Elgin, etc.. Texas
Re: Bore VS Stroke (cgtarga1)
The connecting rod has a mechanical advantage with a longer stroke engine. Just visualize the piston/rod/crank rotating and you can see the one with a longer stroke has better leverage on the crank throw.
Drifting
Joined: Nov 2000
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From: Las Vegas Nevada
Re: Bore VS Stroke (cgtarga1)
The longer the stroke the more TQ it will produce, the shorter the stroke the more revs it will have.
Take 377's for example. Two ways to make it. 400 block, 350 crank, and 350 block with 400 crank. The 350 block will make more TQ, the 400block will have more revs.
Hope this helps some
Take 377's for example. Two ways to make it. 400 block, 350 crank, and 350 block with 400 crank. The 350 block will make more TQ, the 400block will have more revs.
Hope this helps some
Le Mans Master
Joined: Jul 2001
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From: Silicon Valley Kalifornia
Re: Bore VS Stroke (cgtarga1)
For a given bore, the engine with shortest stroke will usually be a top end performer- vice versa for a longer stroke. The long stroke will usually be rated hp wise, at a lower RPM; but will develop more torque rating.
Remember Z28 camaro's of yesteryear...1968? The Z28 302 engine, very short stroke and a bore, I think, the same as the typical 350. The engine was rated at about 6500 rpm...If I remember correctly.
Remember Z28 camaro's of yesteryear...1968? The Z28 302 engine, very short stroke and a bore, I think, the same as the typical 350. The engine was rated at about 6500 rpm...If I remember correctly.
Thread Starter
Burning Brakes
Joined: Oct 2000
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From: My Own Private Idaho
Re: Bore VS Stroke (cgtarga1)
OK,
1. The REASON a long stroke creates torque is because of the smaller angle the rod is to the crank? That makes sense due to leverage.
2. WHY is a shorter stroke capable of higher rpms? Because the shorter travel of the stroke results in lower piston speeds????
I realize this thread won't get the attention a 'What color is your vette' question will, soooo......
I appreciate any enlightenment you can offer.
[Modified by cgtarga1, 12:57 PM 8/8/2001]
1. The REASON a long stroke creates torque is because of the smaller angle the rod is to the crank? That makes sense due to leverage.
2. WHY is a shorter stroke capable of higher rpms? Because the shorter travel of the stroke results in lower piston speeds????
I realize this thread won't get the attention a 'What color is your vette' question will, soooo......
I appreciate any enlightenment you can offer.
[Modified by cgtarga1, 12:57 PM 8/8/2001]
Safety Car
Joined: Mar 2000
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From: Hillsboro OR
Re: Bore VS Stroke (cgtarga1)
The dyno stuff I have seen on this has shown that the shorter stroke motor has the advantage across the rpm range over the longer stroke motor. The main difference comes from the friction losses of the longer stroke motor where the piston speeds are higher.
Burning Brakes
Joined: May 2000
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From: Puyallup Washington
Re: Bore VS Stroke (cgtarga1)
Seat of the pants feeling when boring verses stroking, I always felt more from boring an engine. I don't mean a little, I mean alot! Stroking an engine does not seem to be as good as boring. Now if you bore and stroke, then you have something!
