ive heard several times that the displacement of a stock LT1 really 346. if this is true then when people decide to rebuild em and go say .030 over then how do they figure they have a 355ci displacement? i can see how that would be somewhat correct for a true 350 block going .030 over, but on a 346 wouldnt it end up being like a 351 (with .030 over)? and on a 427 bb block with a .060 overbore what displacement would that be, my friends dad has a 69 SS .060 over on the bottle, i was just wonderin what he has.

 

Let's see.

(3.14/4)*(4^2)*(3.48)*8=349.67~350

Edit-Formula I used is cross sectional area ((pi/4)*D^2)x stroke x # of cylinder if anybody was wondering.

 

Look at the sticky post at the top of the forum for automotive calculations.

 

Good idea.

If you want to be a little more exact, and not have to look things up, try this:

Bore x bore x stroke x number of cylinders x .7854

.7854 is PI/4 accurate to about 5 or 6 decimal places.

HINT: 7854 are the four numbers in the upper left corner of a keypad punched in clockwise, so you don't need to remember the number!

Std 350 has 4.000 bore x 3.480 stroke:

4.000 x 4.000 x3.480 x 8 x .7854 = 349.85 cubic inches

4.030 x 4.030 x 3.480 x 8 .7854 = 355.12

427 had 4.250 x 3.760 stock, right?

4.250 x 4.250 x3.760 x 8 x .7854 = 426.72

.060 over 4.250 is 4.310 or 438.86 cubes

.030 over 4.250 is 4.28 or 432.77 cubes

LS1 has 99.00 mm bore and 92.00 mm stroke.

If you do the math, it's 5665.51 cc's. To convert to cubic inches, multiply by .061. No good memory jogger here.

Oh yeah, it's probably easier on metric engines to calculate the metric dimensioins and convert once rather than converting both bore and stroke to inches.

5665.51 x .061 = 345.6 cubic inches. Maybe that's where you remember 346.

My overly long $.02