How do I calculate cubic inches from bore and stroke? - LS1TECH

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# How do I calculate cubic inches from bore and stroke?

 10-14-2002, 08:18 PM #1 Launching! Thread Starter   Join Date: Nov 2001 Location: Milwaukee Area, WI Posts: 238 How do I calculate cubic inches from bore and stroke? I misplaced my engine calculations book. How do I calculate cubic inches from bore and stroke? i.e. 4.060" bore and 4.000" stroke == ??? ci Also how do I calculate stroke based on rod length and crank info? Thanks, Mike
 10-14-2002, 08:37 PM #2 TECH Fanatic     Join Date: Jun 2002 Location: Upstate NY Posts: 1,979 Re: How do I calculate cubic inches from bore and stroke? Try this site: http://murray.faithweb.com/formulas.htm#find_rear Rod length has nothing to do with determining stroke. Stroke is twice the amount that a rod journal centerline (on the crank) is offset from the main journal centerline.
 10-14-2002, 09:44 PM #3 On The Tree iTrader: (1)   Join Date: Mar 2002 Location: Boise, Idaho Posts: 190 Re: How do I calculate cubic inches from bore and stroke? Pi x (1/2 bore x 1/2 bore) x stroke x 8 = Displacement 3.1416 x (2.03 x 2.03) x 4 x 8 = 414 cu. in. [ October 14, 2002, 09:49 PM: Message edited by: P&DZs ]
 10-14-2002, 09:59 PM #4 Staging Lane   Join Date: Dec 2001 Location: Bay Area, CA Posts: 83 Re: How do I calculate cubic inches from bore and stroke? I use this formula = Bore x Bore x Stroke x # of cylinders x .7854 I like using this formula because the .7854 is easy to remember and makes a little square on the calculator. (simple things for simple minds)
 10-14-2002, 10:41 PM #5 Launching! Thread Starter   Join Date: Nov 2001 Location: Milwaukee Area, WI Posts: 238 Re: How do I calculate cubic inches from bore and stroke? Thanks Guys! Old SStroker - thanks, I thought stroke was affected by rod length. I thought stroke had to do with the distance a piston traveled in the bore (due to crank offset & rod length). Thanks for setting me straight. Mike [ October 14, 2002, 10:47 PM: Message edited by: Brownie ]
 10-14-2002, 11:29 PM #6 Launching!   Join Date: Nov 2001 Location: Plano, TX Posts: 246 Re: How do I calculate cubic inches from bore and stroke?
quote:
Originally posted by Brownie: Thanks Guys! Old SStroker - thanks, I thought stroke was affected by rod length. I thought stroke had to do with the distance a piston traveled in the bore (due to crank offset & rod length). Thanks for setting me straight. Mike
Well you're right that the stroke is the distance travelled by the piston - it's just that rod length has no effect on this, as Old stroker pointed out. The stroke is entirely determined by the crankshaft.
 10-14-2002, 11:34 PM #7 Launching! Thread Starter   Join Date: Nov 2001 Location: Milwaukee Area, WI Posts: 238 Re: How do I calculate cubic inches from bore and stroke?
quote:
Originally posted by Red2000SS:
quote:
Originally posted by Brownie: Thanks Guys! Old SStroker - thanks, I thought stroke was affected by rod length. I thought stroke had to do with the distance a piston traveled in the bore (due to crank offset & rod length). Thanks for setting me straight. Mike
Well you're right that the stroke is the distance travelled by the piston - it's just that rod length has no effect on this, as Old stroker pointed out. The stroke is entirely determined by the crankshaft.
Gotcha! Thanks. Had to think about that a minute, it makes perfect sense now. Mike [ October 14, 2002, 11:42 PM: Message edited by: Brownie ]
 10-15-2002, 05:22 AM #8 On The Tree   Join Date: Nov 2001 Location: Gold Coast Australia Posts: 164 Re: How do I calculate cubic inches from bore and stroke?
quote:
Originally posted by Black Magic: I use this formula = Bore x Bore x Stroke x # of cylinders x .7854 I like using this formula because the .7854 is easy to remember and makes a little square on the calculator. (simple things for simple minds)
Your close, but no cigar. I 'spose close enough is good enough for simple minds tho'
 10-15-2002, 07:10 AM #9 TECH Fanatic     Join Date: Jun 2002 Location: Upstate NY Posts: 1,979 Re: How do I calculate cubic inches from bore and stroke?
quote:
Originally posted by v8 ute:
quote:
Originally posted by Black Magic: I use this formula = Bore x Bore x Stroke x # of cylinders x .7854 I like using this formula because the .7854 is easy to remember and makes a little square on the calculator. (simple things for simple minds)
Your close, but no cigar. I 'spose close enough is good enough for simple minds tho'
Volume of a cylinder is diameter times diameter times length(stroke) times [Pi divided by 4]. Pi/4 is .785398163 so .7854 is 99.9997661% correct. That's about 8/10,000 (.0008)of a cubic inch on an LS1. That's close enough even for professional racing organizations, as well as being simple to remember. The "little square" as a memory technique never occurred to me. That's elegant, Black Magic! Thanks. [ October 15, 2002, 11:31 AM: Message edited by: Old SStroker ]
 10-15-2002, 01:36 PM #10 On The Tree   Join Date: Mar 2002 Location: Maple Grove, MN Posts: 174 Re: How do I calculate cubic inches from bore and stroke? Bore * Bore * Stroke * 6.2832 = CI for a 8 cylinder.
 10-15-2002, 01:42 PM #11 Wheels up Director iTrader: (11)     Join Date: Nov 2001 Location: Mantua, NJ Posts: 886 Re: How do I calculate cubic inches from bore and stroke? Well I sometimes forget where I left my calculator so THIS makes it alot easier on me LAter
 10-15-2002, 04:19 PM #12 Dumb Ass Vette Moderator iTrader: (20)     Join Date: Jun 2002 Location: Colorado Posts: 4,246 Re: How do I calculate cubic inches from bore and stroke? An LS1 is made up of 8 cylinders. Volume of cylinder is v = pi * ( radius/2 )^2 * height So, the total volume of the motor be CID = 8 * v Or you can just use the following Engine Calculator
 10-15-2002, 04:32 PM #13 TECH Enthusiast iTrader: (1)   Join Date: Apr 2002 Location: Dallas-freakin'-Texas Posts: 716 Re: How do I calculate cubic inches from bore and stroke? Brownie- the stroke DOES determine how far the piston moves up and down the bore, but the length of the rod has nothing to do with how far the piston travels, only "where" it travels. In any event, my displacement calculation formula is as follows: (bore/2)^2 * pi * stroke * cylinder count. So your example of an 8 cylinder motor with a 4.06" bore with a 4" stroke would calculate like this: (4.06/2)^2 * 3.1415927 * 4 * 8 = 414.278 cubes. Really, all of the formulas people have recited are just different permutations of the same concept... gotta first find the area of the bore, multiply that by the stroke to get cylinder volume, then multiply that by the number of cylinders. [ October 15, 2002, 04:40 PM: Message edited by: BurnOut ]
 10-15-2002, 07:55 PM #14 Launching! Thread Starter   Join Date: Nov 2001 Location: Milwaukee Area, WI Posts: 238 Re: How do I calculate cubic inches from bore and stroke? Thanks guys! Great info. I appreciate gettin me squared away. Volume of a cylinder Stroke makes perfect sense now and I see how the rod length has nothing to do with the distance it travels. Mike

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