Can any propeller heads out there tell me the displacement of a 4K-C with 060 oversize pistons?

1342cc

75mm stock bore, + 1.5mm (60 thou). 73mm stroke. That's all you need to know to punch into a displacement calculator 😉

The volume of a single cylinder is Pi x r squared x the stroke.

22/7 x bore/2 x bore/2 x stroke.

For a standard 4K engine, the bore is 75mm & the stroke is 73mm

Substituting these into the above equation give (22/7) x (75/2) x (75/2) x 73 =  3.1429 x 37.5 x 37.5 x 73 = 322638.33 cu mm

Divide that by 1000 to obtain cubic centimeters & you obtain 322.64 cu cm.

That is for one cylinder. To calculate that for 4 cylinders, simple multiple by four.

322.64 x 4 = 1290.56 cc, which is what the good book says the capacity is for a standard 4K engine.

Now simply add 1.524mm (60 thou) to the bore dimension, & recalculate. 

3.1429 x (75.00+ 1.524)/2 x (75 +1.524)/2  x 73 = 3.1429 x 38.26 x 38.26 x 73 =   335.85 cu cm

Multiple that by 4 & you get a new volume of 1343.4 cc.

Subtract the original standard volume = 1343.40 - 1290.56 = 52.84 cc.  or an extra 13.21 cc to each cylinder's swept bore capacity.

Yep, basically, the same as Simons calc.

Cheers Banjo

 

Edited May 17, 20251 yr by Banjo

I appreciate your response and info, much appreciated mate, cheers 

Hi Tony,

              My guess is; that now You will want to calculate the new "compression ratio", of your 60 thou bored engine.  This is a little more complicated, depending on whether you have flat top pistons; or pistons with domed or concave top faces.

This calculation, should also take into account the thickness of the head gasket, once torqued down, to be truly accurate.

Here is a variety of sites tackling this question, if Your interest  requires this information. 

How to Calculate the Compression Ratio

Obviously, if you bore the engine, & leave the combustion area in the head untouched; the compression ratio, will increase.  Question is; by how much ?

This link here on Rollaclub, from over a decade ago, might help ?

https://www.rollaclub.com/board/topic/69246-4k-engines/

Cheers Banjo

Edited May 18, 20251 yr by Banjo