bore vs stroke

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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.
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Ummmm, 440 & the 426 wedge or Hemi have the same stroke ....
Ahhhhh... right?????
LMAO
 
krazykuda said:
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...
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Exactly! That would be fun!
I’d have a riot on intakes alone!
 
MOPAROFFICIAL said:
You do realize 426 is a shorter stroke and smaller bore than a 440 right?
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The 426 and 440 are the same stoke and different bores...

The 400 has a larger bore with a shorter stroke than the 440... That's why many people build stroker big block engines out of the 400 vs the 440....
 
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???
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Cause the Hemi is a built more performance wise. Build both to the same level “hp” and the 440 will make more torque, plus that factory rates not the most reliable source for power ratings.
 
krazykuda said:
All 426 Hemi and wedge and 440 have the same stroke - 3.75"...
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Yea, I know, LMAO! Thanks anyway. Ha ha ha ha ha
273 said:
Cause the Hemi is a built more performance wise. Build both to the same level “hp” and the 440 will make more torque, plus that factory rates not the most reliable source for power ratings.
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Oh boy! Drinking the cool air again I see.
So off base.....
 
273 said:
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.
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You have to keep in mind that the bore has exponential influence on volume than stroke... Area = Pi * radius squared... Radius is half the bore, so radius has more influence on volume than stroke, therefore the radius is not a 1:1 influence vs stroke on volume... Radius is bore halved, then you square it to get volume...
 
273 said:
Cause the Hemi is a built more performance wise. Build both to the same level “hp” and the 440 will make more torque, plus that factory rates not the most reliable source for power ratings.
Click to expand...

Yes, and the Hemi heads breathe much better than the wedge heads...
 
Last edited:
krazykuda said:
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...
Click to expand...

should produce the similar hp just at different rpm. The 340 is gonna need a bit more stall and gears than similar 360.
 
MOPAROFFICIAL said:
. The same heads between two engines.....the shorter stroke will act as if it has bigger heads.
Click to expand...

A shorter stroke will rev faster than longer stroke... But longer stroke will develop more torque at lower RPM...

It's kinda like the chicken vs the egg argument...

That's why it would be a great experiment to build a 340 and 360 with identical components to see how they compare to each other...
 
krazykuda said:
A shorter stroke will rev faster than longer stroke... But longer stroke will develop more torque at lower RPM...

It's kinda like the chicken vs the egg argument...

That's why it would be a great experiment to build a 340 and 360 with identical components to see how they compare to each other...
Click to expand...

Simply isnt enough of a window at higher rpm to feed the long arm. That's the point.

Typo was, while on talk to text, my neighbor asking if the 426 had a shorter stroke than a 440 after i read aloud some replies.

2.1 rod stroke ratio is the thing high rpm dreams are made of... f1
383 just happens to be in the 1.80's rod ratio bracket..
 
krazykuda said:
A shorter stroke will rev faster than longer stroke... But longer stroke will develop more torque at lower RPM...

It's kinda like the chicken vs the egg argument...

That's why it would be a great experiment to build a 340 and 360 with identical components to see how they compare to each other...
Click to expand...
Hence why I build the 360 for my street bound rides. It also peaks (HP) a little earlier.
 
krazykuda said:
You have to keep in mind that the bore has exponential influence on volume than stroke... Area = Pi * radius squared... Radius is half the bore, so radius has more influence on volume than stroke, therefore the radius is not a 1:1 influence vs stroke on volume... Radius is bore halved, then you square it to get volume...
Click to expand...

Is not about volume but the surface area of the piston. The more surface area the more the expansing gassed can push against the piston.
 
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.
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R/S ratio matters on induction limited stuff, quite the contrary to David Reher and his vehement opposition to Rod ratio and its affects.

Chrysler did the research on this. So did many others. If you in an unlimited induction engine, then it doesn't matter much.
 
MOPAROFFICIAL said:
Simply isnt enough of a window at higher rpm to feed the long arm. That's the point.
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Not when you're talking small differences between bore and stroke...

When you overbore it's usually in .010" increments... that's not much to influence the burn in the engine...

Plus the thing to keep in mind here is the engine uses the otto cycle of thrermodynamics... It's the pressure that you can develop in the cylinder that determines the push on the piston... Similar pressure will have similar push on the piston... The stroke "amplifies" the force of the push downward on the piston as the crank turns...

But if you go overboard (no pun intended) on the stroke and make it too long vs the bore area, then the pressure and force on the piston are reduced and the flame travel will be reduced... That's why you have to balance bore vs stroke for the best performance...
 
krazykuda said:
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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Under square? Is that what your "professor" said? I hope not.
 
273 said:
Is not about volume but the surface area of the piston. The more surface area the more the expansing gassed can push against the piston.
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I got something for ya...


If both MoPar 383 engines (B vs RB 383) with otherwise the same parts, who makes more power? Consider the parts used to be only factory parts and we are not chasing power with mondo huge cams and trick parts etc...
Both have the same small valve heads and valves.

Since both breath in the same amount of air and fuel, doesn’t the same amount of air and fuel in a smaller concentrated area have a better chance of pushing the piston downwards in the smaller bore rather than spread out over a larger area?
 
MOPAROFFICIAL said:
2.1 rod stroke ratio is the thing high rpm dreams are made of...
Click to expand...

Rod to stroke ratio is different than bore to stroke ratio...

Then use a 1.2 bore to stroke ratio and a 2:1 rod to stroke ratio for optimum...
 
rumblefish360 said:
I got something for ya...


If both MoPar 383 engines (B vs RB 383) with otherwise the same parts, who makes more power? Consider the parts used to be only factory parts and we are not chasing power with mondo huge cams and trick parts etc...
Both have the same small valve heads and valves.

Since both breath in the same amount of air and fuel, doesn’t the same amount of air and fuel in a smaller concentrated area have a better chance of pushing the piston downwards in the smaller bore rather than spread out over a larger area?
Click to expand...

There is no RB 383... The 383 is an R motor with 3.375" stroke.... The RB engines have a 3.75" stroke...

You would want to compare identically built 383 vs 426 wedge engines to see the effect of stroke on bore size alone...

383 = 4.25" bore and 3.375" stroke...
426 = 4.25" bore and 3.75" stroke...
 
krazykuda said:
A shorter stroke will rev faster than longer stroke... But longer stroke will develop more torque at lower RPM...

It's kinda like the chicken vs the egg argument...

That's why it would be a great experiment to build a 340 and 360 with identical components to see how they compare to each other...
Click to expand...



Have you EVER been to a drag strip? How about a dyno? You can't believe half the crap you are posting can you?

If you do, you'd better get on the phone and call Greg Anderson and Jason Line. Because they build **** *** backwards from what you think.

Surely, you can coach them up.
 
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