Author Topic: Engine Displacement Math (Read 2934 times)

liv2ride · « **on:** July 27, 2013, 03:35:37 PM »

What is the formula for figuring engine displacement?
78MM Bore X 76MM Stroke

yaegerb · « **Reply #1 on:** July 27, 2013, 03:41:04 PM »

Quote from: liv2ride;6040

What is the formula for figuring engine displacement?
78MM Bore X 76MM Stroke

bore x bore x stroke x .7854

so if you convert it to CC's your equation is 7.8 x 7.8 x 7.6 x .7854 = 363.15 or 363 for rounding purposes.

Pumashine · « **Reply #2 on:** July 27, 2013, 04:49:49 PM »

What is stock stroke for the 250r? I was wondering how you got the 76mm stroke?

yaegerb · « **Reply #3 on:** July 27, 2013, 05:07:19 PM »

I know the stock stroke on the 85 and 86 engines but not the 87-89

85 and 86: 72MM

if it was one of the above model engine, he must have added a +4 rod.

liv2ride · « **Reply #4 on:** July 27, 2013, 05:25:22 PM »

Correct. '86-'89 are all 66X72

For this (350PV) build I added a +4mm crank.

Hindsight shows me my $ would have been better spent on good quality port work. My 330 non-PV outperforms the 350PV in every aspect of performance.

IMO the extra stroke takes away the engines ability to get into the real high RPM's. That's what I love about the R's

Polonda · « **Reply #5 on:** July 27, 2013, 06:13:36 PM »

http://www.csgnetwork.com/cubicinchcalc.html

make sure to select mm and 1 cylinder obviously. Enter bore and stroke. Leave the rest blank.