Overbore adds C.I. ?

[powerband]

I hadn't thought about this before but I will ask the Hardcore crew:

My 250 mill was bored .070 over and uses 10:1 pistons with @21cc dish.

Someone I mentioned this to said that added up to more C.I.'s. I hadn't thought about it but I guess it did add something to the displacement.

Anyone got a realistic ballpark figure what the .070 overbore and 21cc vs typical (@7cc's?) dished pistons would add to the displacement?

Thanks

Powerband

 

[ASMART]

Boring adds displacement, different pistons do not. Since diplacementis different, so will the comp ratio given the same piston top.

 

[rbohm]

8) a .070 overbore wil add about 9ci on a six cylinder engine.

 

[69Falcon]

Disp.=Bore x Bore x Stroke x 4.712

The 4.712 takes into account the # of cylinders (6), pi (3.14159) and a conversion factor to calculate area from the bore diameter. Here's a calculator.

 

[XPC66]

Boring adds displacement, different pistons do not. Since diplacementis different, so will the comp ratio given the same piston top.

Oversize pistons generally have a lower compression height to maintain CR.

 

[ASMART]

Just a reminder that increasing bore can increase compression.

 

[BaldvinE]

Disp.=Bore x Bore x Stroke x 4.712

Why the 4.712? What's wrong with just :

(Bore/2)^2 * π * stroke * Number of cylinders = Total displacement

This works for any engine, no specialized constant

 

[rbohm]

Disp.=Bore x Bore x Stroke x 4.712

Why the 4.712? What's wrong with just :

(Bore/2)^2 * π * stroke * Number of cylinders = Total displacement

This works for any engine, no specialized constant

basically 69falcon simplified the formula so that you use one constant for 6 cylinder engines.

 

[BaldvinE]

Yeah, I know, it's just that it takes the logic out of the equation so you can't adapt it to anything else, as you can't see the principals being used.

So I just put that up to clarify what calculations are actually being done, so as to make it easier to understand.

I don't know, seemed like a good idea at the time, at least

 

[rbohm]

8) try this one then;

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