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Discussion Starter · #1 ·
Hypothetically speaking: If we are after low end grunt, would increasing just the bore on a 1250 CVO, to say the bore used on the 1440 kit, or even the 1550, but w/out the stroke, yield good results? Is that much "under square" necessarily a bad thing? Isn't that how the 1250 motor was born and also the new 110ci CVO airheads?
:hmm:
 

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bikerabbi said:
Hypothetically speaking: If we are after low end grunt, would increasing just the bore on a 1250 CVO, to say the bore used on the 1440 kit, or even the 1550, but w/out the stroke, yield good results? Is that much "under square" necessarily a bad thing? Isn't that how the 1250 motor was born and also the new 110ci CVO airheads?
:hmm:
I don't think you'll get the torque without the longer levers. (Stroke)

Increasing bore will increase the torque, to a degree, but if you want torque, you want the longer lever.

Being "under square" allows you to rev higher, but horsepower peak will be at the upper rpm bands, like the V-Rod.
 

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bikerabbi said:
Hypothetically speaking: If we are after low end grunt, would increasing just the bore on a 1250 CVO, to say the bore used on the 1440 kit, or even the 1550, but w/out the stroke, yield good results? Is that much "under square" necessarily a bad thing? Isn't that how the 1250 motor was born and also the new 110ci CVO airheads?
:hmm:
An engine is considered "oversquare" if it's bore/ stroke ratio is greater than 1.0. Increasing the bore will make an oversquare engine even more so, assuming the stroke remains constant.
 

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Discussion Starter · #4 ·
JustSam said:
An engine is considered "oversquare" if it's bore/ stroke ratio is greater than 1.0. Increasing the bore will make an oversquare engine even more so, assuming the stroke remains constant.
Hmmm, OK, then will making it that much "oversquare"necessarily be a bad thing?
 

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The bore on the 1550 and 1450's are the same. They got more displacement using a 1/2" and 1/4" stroker crank. So what I'm saying is that the 1320 kit from Wiseco is the same bore as the 1550 and 1450 (or is it 1430) just stroked to make more displacement.
 

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bproulxvrod said:
So what I'm saying is that the 1320 kit from Wiseco is the same bore as the 1550 and 1450 (or is it 1430) just stroked to make more displacement.
It is actually a 1434cc if you look at the technicalities. The 4.250" bore will make a 1320, 1434 or a 1550 when using a stroke of stock, +1/4", and +1/2" respectively.
 

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Darth Veeness
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Having an oversquare engine isn't a bad thing. It just gets you different function than a square or undersquare engine. Oversquare motors are horsepower motors whereas undersquare motors are torque motors. It's the stroke that makes torque because on the power stroke the longer it takes the rod to go from it's position at sparkplug fire to bdc the longer the "power" is on, in this case meaning torque.
 

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nic_a_bod said:
Anybody else besides eagle destroke the motor? I thought that it created all kinds of power.
It did, high end power, not really streetable. This is one of the reasons AHDRA requires stock stroke cranks in the V-Rod class.
 

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let me throw in a monkey wrench. in one of the big car magazines they did a comparison of long stroke versus short stroke with the same dispacement . the short stroke motor made more torque, go figure
 

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there are more variables to consider in such an equation.......intake plenum volume and length, exhaust efficiency, cam profile and timing, etc etc.....
assuming the same intake runners/head geometry is used on both motors....
a "sweet spot" or good combination with one displacement will likely not be a good combination for another displacement.....
 

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Discussion Starter · #12 ·
o2man98 said:
It is actually a 1434cc if you look at the technicalities. The 4.250" bore will make a 1320, 1434 or a 1550 when using a stroke of stock, +1/4", and +1/2" respectively.
Still, I'm talking about increased torque. For example, the
96 ci airhead at 3.75 X 4.38 = 86ft/lb.
SE 110 ci airhead at 4.00 x 4.38= 110 ft/lb

A wopping difference in torque by just increasing the bore 1/4 in.

the V-Rod 1130 cc is 3.94 x 2.84 = 74 ft/lb.
the 1250 cc is 4.13 x 2.83 = 85 ft/lb.

The airhead increase is a full 24 ft/lb increase.
The V-Rod increase is a mere 11 ft/lb increase. On all the models the stroke stayed the same. Are our models capable of a 24 ft/lb increase by just upping the bore some more while leaving the stroke alone? I'd be happy (so I say!) with the same hp while getting a 24 ft/lb increase in torque (actually 13 more ft/lb over the 1250 engine.).
 

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bikerabbi said:
Still, I'm talking about increased torque. For example, the
96 ci airhead at 3.75 X 4.38 = 86ft/lb.
SE 110 ci airhead at 4.00 x 4.38= 110 ft/lb

A wopping difference in torque by just increasing the bore 1/4 in.

the V-Rod 1130 cc is 3.94 x 2.84 = 74 ft/lb.
the 1250 cc is 4.13 x 2.83 = 85 ft/lb.

The airhead increase is a full 24 ft/lb increase.
The V-Rod increase is a mere 11 ft/lb increase. On all the models the stroke stayed the same. Are our models capable of a 24 ft/lb increase by just upping the bore some more while leaving the stroke alone? I'd be happy (so I say!) with the same hp while getting a 24 ft/lb increase in torque (actually 13 more ft/lb over the 1250 engine.).
Your forgetting they changed cams with both those packages. The 1250 cam has 6 degrees less overlap so better for torque then the 1130 cam. It probably makes more difference then the displacement did. IMHO
 

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RICK
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Stroke will help torque, but the longer stroke will reduce reliability. As for bore, I've machined the 1130cc cases, and there isn't any more room for a larger bore(4.25). What we need is a larger, stronger set of engine cases to allow for higher hp motors with stroke and bore. But Mike Lewis hit it on the head. There is more to it than just stroke or just bore!
 

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RNTRACING said:
Stroke will help torque, but the longer stroke will reduce reliability. As for bore, I've machined the 1130cc cases, and there isn't any more room for a larger bore(4.25). What we need is a larger, stronger set of engine cases to allow for higher hp motors with stroke and bore. But Mike Lewis hit it on the head. There is more to it than just stroke or just bore!
I thought that the 1600 had a 4.350 bore???
 

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Vinny said:
I thought that the 1600 had a 4.350 bore???
I didn't break out a micrometer but I have one of BADROD's 1700 cc liners here that measures just a hair under 4.5 inches. I don't think it had any water passages at all. :)
 

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Greg/Moderator
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Here you go straight from "The Man"....... Paul D.

4.440 bore with 3.335 stroke is over 100 inches
4.375 bore with 3.335 stroke is over 100
4.350 bore with 3.585 stroke is over 100
4.680 bore with 3.071 stroke is over 100
4.440 bore with 3.585 stroke is way over 100
I think I have parts for all these combos I stock if your really ready for a challange???????
 
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