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eurotrash
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Well, apparently this thing had a total rebuild and pump recalibration about 12 years ago. The pump has Precisions medallion on it, the motor has a 1mm over bore, and the head looks yellowed from oil, but not black as you would see in an original.

Interesting.

What's a 1mm over bore net you in displacement?

2.2 ishness?

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Using geometry, I get the following displacements:

Stock:

Bore (diameter of piston) = 89.00mm

Stroke (distance piston moves up and down in cylinder) = 80.00 mm

Displacement = Pi(r^2)(stroke) X 4 cylinders

= 3.14159265 X 0.445^2 X 0.800 X 4

= 1.9907 liters

1 mm overbore:

Bore (diameter of piston) = 90.00mm

Stroke (distance piston moves up and down in cylinder) = 80.00 mm

Displacement = Pi(r^2)(stroke) X 4 cylinders

= 3.1415926 X 0.45^2 X 0.800 X 4

= 2.0357 liters

Your pistons are marked 89.96 (assuming mm), which nets you:

Displacement = Pi(r^2)(stroke) X 4 cylinders

= 3.1415926 X 0.4498^2 X 0.800 X 4

= 2.0339 liters

To get to 2.2 liters you need to increase the bore to 94:

Displacement = 3.14159265 X 0.47^2 X 0.800 X 4

= 2.2207 liters

Someone should check my arithmetic, but that's the simplest version of the calculation. It assumes no machining, etc.

Grice

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= quality answer.

I like your style here, Grice. (math > internet 'wisdom')

Using geometry, I get the following :

Your pistons are marked 89.96 (assuming mm), which nets you:

Displacement = Pi(r^2)(stroke) X 4 cylinders

= 3.1415926 X 0.4498^2 X 0.800 X 4

= 2.0339

Grice

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Thanks, Ken. I actually had to look up the equation for calculating the volume of a cylinder. It's been more than 20 years since I put down my mathematics texts, changed my major(s) from engineering and math to accounting and finance, and became an accountant at Arthur Andersen. This should not be considered an expression of guilt, nor an explanation for how some minor arithmetic errors may have found their way into the financial statements at Enron.

Coincidentally, I watched all of your vintagebmwracing videos earlier tonight, along with Marshall Lytle's and a few other FAQers'. Excellent fun! Do you have more video of your car online?

Grice

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I talk to customers all day long about making bigger motors by adding bore and stroking cranks so I use this simple formula that gets you really close:

MMbore x MMbore x 0.7854 x MMstroke x number of cylinders / (div) 1000 = displacement in liters.

Quick and dirty....

Patman

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