bore vs stroke

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dibbons said:
Based on the video and my calculations, the Mopar small block RPM potential would be 9,000 RPM.
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Haaaaaaaaaa Haaaaaaaaa haaaaaa haaaaaa.

It's doable, but with the 59 degree LBA and the screwed up oil timing you have a very narrow widow to make it live. By narrow I mean >< and that's about twice as wide as it should be.
 
I've never owned an engine with an 86mm bore or stroke and don't plan on it.

Too many maybes, likelys and abouts in his schpiel for me to take him seriously.
 
video-bore-vs-stroke-which-one-is-worth-more-power-2020-01-10_18-40-52_344509-960x640.jpg


Wait, what? 3.58 stroke is 90.9mm, ( 1inch being 25.4mm)
(90.9x2)x(7200/60)= 21816m/s
WTH does that mean?
I think they forgot a conversion factor to change mm to meters: so divide by 1000=21.8m/s badaboom. I guess that's why my6014 mm engine, has survived this long,lol, I'm only at 87% yet..........lol.
 
Krooser said:
I've never owned an engine with an 86mm bore or stroke
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86mm is 3.386 inches, so a lil more than the standard 3.315 SBM stroke; but not quite as much as a 3.58 from a 360..
But even the 273 has a bigger bore at 3.63or ~92mm
But lessee, to be square a 3.58 stroke 273 is almost there,lol. That's 296 cubes
And the 408 starts out life as a 4x4
Jus ruminating...
 
Some flaws I see in the video...

It's hard to keep torque constant... Longer stroke will give more torque - that's the definition of torque...

They use a valve lift of 5 mm, most cams are just under or above .5 inch lift... Port flow usually is greater above .400 inch lift....
 
The efficiency of the engine is directly related to compression...

Here is an explanation from a Yale professor....

 
krazykuda said:
Some flaws I see in the video...

It's hard to keep torque constant... Longer stroke will give more torque - that's the definition of torque...
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Torque would be somewhat constant, even though longer stroke has more multiplying effect over shorter stroke. But smaller bore will have less surface area so less pounds per square inch being applied to the crank to be multiplied.

Torque has more to do with displacement than how that displacement is constructed eg.. bore and stroke.

For power, engines with similar displacement the bigger bore will have more advantage than longer stroke.
 
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383 Chevy vs. 383 Mopar! - Engine Masters Ep. 3
This was the only place I found this video:

 
You know you're going to hurt the slant crowds feelings with this..
That's why they ultimately fall short. ...Besides the 2 cylinders missing and valves smaller than a 318...and an intake comprised of 6 reeds from a mote... lol

I really like the 4" sb ...its power, like right now...but the 340 is getting another go .
 
273 said:
Torque would be somewhat constant, even though longer stroke has more multiplying effect over shorter stroke. But smaller bore will have less surface area so less pounds per square inch being applied to the crank to be multiplied.

Torque has more to do with displacement than how that displacement is constructed eg.. bore and stroke.

For power, engines with similar displacement the bigger bore will have more advantage than longer stroke.
Click to expand...

No, stroke directly affects torque by the definition of torque... Force times perpendicular distance... The longer the stroke, the more the perpendicular distance, hence the more torque...

Just like using a pry bar - the longer the pry bar, the more torque it produces...
 
But the funny thing is, the engine masters video refutes that. The short stroke BBM made more torque over a broader span than the long stroke Chevy.
I was surprised.
krazykuda said:
No, stroke directly affects torque by the definition of torque... Force times perpendicular distance... The longer the stroke, the more the perpendicular distance, hence the more torque...

Just like using a pry bar - the longer the pry bar, the more torque it produces...
Click to expand...
 
krazykuda said:
No, stroke directly affects torque by the definition of torque... Force times perpendicular distance... The longer the stroke, the more the perpendicular distance, hence the more torque...

Just like using a pry bar - the longer the pry bar, the more torque it produces...
Click to expand...

Yes but your not accounting a smaller pistons is gonna have less force against the longer stroke than a larger piston against shorter stroke.
Stroke is only one part of the equation.

Eg.. A weak man with a longer pry bar vs a strong man with a shorter pry bar could be made to be even depending on the lengths.
 
rumblefish360 said:
But the funny thing is, the engine masters video refutes that. The short stroke BBM made more torque over a broader span than the long stroke Chevy.
I was surprised.
Click to expand...

273 said:
Yes but your not accounting a smaller pistons is gonna have less force against the longer stroke than a larger piston against shorter stroke.
Stroke is only one part of the equation.

Eg.. A weak man with a longer pry bar vs a strong man with a shorter pry bar could be made to be even depending on the lengths.
Click to expand...


Assuming everything else is constant...

Bore will also affect how well the mixture burns, as long as the bore doesn't limit the flame propagation and expansion of the mixture....

Larger bore than stroke will help the engine rev faster, but longer stroke will develope more stroke on the same bore... It's a balance between bore vs stroke... It would be interesting to build identical 340 vs 360 and race them against each other to see how the bore vs stroke affects the output....

My engine professor taught us that the most desireable bore to stroke ratio is 1.2 bore vs stroke...
 
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rumblefish360 said:
But the funny thing is, the engine masters video refutes that. The short stroke BBM made more torque over a broader span than the long stroke Chevy.
I was surprised.
Click to expand...

you need to compare on identical engines, not mopar vs chevy, there are too many other variables that can play into the results...
 
273 said:
Yes but your not accounting a smaller pistons is gonna have less force against the longer stroke than a larger piston against shorter stroke.
Stroke is only one part of the equation.

Eg.. A weak man with a longer pry bar vs a strong man with a shorter pry bar could be made to be even depending on the lengths.
Click to expand...

Yes, it the bore affects how well the mixture burns, but if the mixture can burn properly more stroke will give you more torque...
 
rumblefish360 said:
But the funny thing is, the engine masters video refutes that. The short stroke BBM made more torque over a broader span than the long stroke Chevy.
I was surprised.
Click to expand...


273 said:
Yes but your not accounting a smaller pistons is gonna have less force against the longer stroke than a larger piston against shorter stroke.
Stroke is only one part of the equation.

Eg.. A weak man with a longer pry bar vs a strong man with a shorter pry bar could be made to be even depending on the lengths.
Click to expand...


An example is the 440 six pack vs the 426 Hemi... Both engines were rated at 495 ft*lbs of torque and has the same stroke... If bore had more influence on torque why wasn't the 440 putting out more torque???
 
krazykuda said:
you need to compare on identical engines, not mopar vs chevy, there are too many other variables that can play into the results...
Click to expand...
Just throwin **** out there....
It is a far comparison based on cubic inches only.
I would love to run into enough money to throw away on your very cool idea. And try various cams, heads, etc....
340 vs 360 showdown shoot out!!!
Screw it, while I’m day dreaming of screwing off with my mega millions win fall, I might as well include a 408.
:rofl:
Beer and pizza on me at the dyno room!
 
krazykuda said:
Yes, it the bore affects how well the mixture burns, but if the mixture can burn properly more stroke will give you more torque...
Click to expand...

yes but 2 engines with the same displacement but different bore and stroke, the one with a smaller bore is gonna have less force pushing the pistons down.
Since the expanded gases have less area to push on.
 
krazykuda said:
An example is the 440 six pack vs the 426 Hemi... Both engines were rated at 495 ft*lbs of torque and has the same stroke... If bore had more influence on torque why wasn't the 440 putting out more torque???
Click to expand...
. The same heads between two engines.....the shorter stroke will act as if it has bigger heads.
 
rumblefish360 said:
Just throwin **** out there....
It is a far comparison based on cubic inches only.
I would love to run into enough money to throw away on your very cool idea. And try various cams, heads, etc....
340 vs 360 showdown shoot out!!!
Screw it, while I’m day dreaming of screwing off with my mega millions win fall, I might as well include a 408.
:rofl:
Click to expand...

I agree... It would be great to build identical 340 and 360 engines and compare.... Then change cams, heads, etc to see how they influence the output...
 
MOPAROFFICIAL said:
You do realize 426 is a shorter stroke and smaller bore than a 440 right? And the 426 couldn't beat the 440 until you gave her enough gear to rev ...so here you go ,shorter stroke reving higher will beat the long stroke bigger bore.

That's a couple things way better heads and RPM...
however... The same heads between two engines.....the shorter stroke will act as if it has bigger heads.
Click to expand...

Both the 426 and the 440 have 3.75" stroke... Look it up...

The cranks are interchangeable... That's why many people who sell their Hemis keep the Hemi crank and substitute the 440 crank...
 
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