small bore x long stroke + NOS = big hp !

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small bore x long stroke + NOS = big hp !

Postby provega » Mon Dec 07, 2009 4:39 am

After several years of building small block chevrolets, I finally settled on a 396 cu in smallblock that ran harder than anything I ever built. With the bigger bore motors and the 3.875" stroke, I made good power, but when I used the same stroke with a smaller bore and equal amount of nitrous, things really came to life. I figured that the smaller bore had no choice but to make more horsepower because of the smaller combustion area being given the same amount of fuel and Nitrous. Make sense ? Anybody have the same results or theory ?
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Re: small bore x long stroke + NOS = big hp !

Postby chevyart » Tue Dec 08, 2009 8:12 pm

just out of curiousity, what rpm range are you wotking that motor in. i had always thought when you used the biggest bore possibe, combined with big valves, thast ther was no better way, but this is probably in the higher rpm scale. maybe down lower you smaller bores acts lilk a stroker motor and produces all the power down low, especially with the juice. im curious what the other guys say chevy art
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Re: small bore x long stroke + NOS = big hp !

Postby Ishiftem » Wed Dec 09, 2009 12:14 am

Assuming EVERYTHING except the bore is the same,your theory is wrong provega. The combustion area is the same. With the piston at TDC, and assuming the compression height is the same, the area that the fuel mixture is squeezed into is the same. Actually what you have done is lower the compression ratio. The smaller bore will pull in less air/fuel than the larger bore and squeezes that lesser amount into the same size space. My theory, and it's just a theory, is that you were not making optimal power due to detonation before. You don't have to hear it for it to be happening. The smaller bore effectively lowered the compression ratio, thus eliminating the detonation allowing the motor to make power to it's full potential. Assuming everything else about the motors is identical. Just a thought off the top of my head. It does make a guy think though.
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