wildcat077

Holytin

That would be a reduction of 23.6 ccm. - 2477 ccm to 2453 ccm. Hope that helps.

Arominus

55cc without the cut on an 8v.

Holytin

Sorry, Arominus, but I don't see how you come up with 55 cc's. Here are the relevant engine specs for our calculations - let's start and calculate engine displacement, which is 2,479 cc's for the 8V 2.5 liter engine:

1. Bore - 100mm
2. Stroke - 78.9 mm

Formula:

Piston area x stroke x number of cylinders = 3.14159 x 5^2 x 7.89 x 4 = 2,479 cc

Bingo, formula is correct...

Now, let's calculate engine displacement based on "shaving off" 0.030". To complete this calculation we must convert to metric - 0.030" equals 0.75mm, which we must deduct from 78.90 mm (stroke). That's 78.15mm

Piston area x stroke x number of cylinders = 3.14159 x 5^2 x 7.815 x 4 = 2,455 cc

Now we deduct 2,455 cc's from 2479 cc's and the result is 24 cc's. Sorry for the inaccuracies in my earlier calculation but I only used 3.14 for the constant number pi...

So, how did you come up with 55 cc's...

V2Rocket

55-60cc is the measured combustion chamber volume of an 8v 944 head.

the OP asked what the CC change in combustion chamber volume would be by cutting the cylinder head.
nothing to do with the engine stroke like your math is suggesting.

the OP could shave 0.030" off his head and still have a 2479cc engine.

Holytin

Arominus

You are making the assumption that the stroke is reduced, but it is not. Stroke is determined by the throw on the crank, not the height of the head. All the OP is doing by shaving the head is reducing the area that the air is being compressed into, the bore is also unchanged so the the displacement is the same. Hes increasing the compression by milling the head, nothing more. The only way to change the stroke would be to offset grind the crank in the opposite direction that normal people offset grind a crank.

Considering the variation that Spencer quoted, i would say the only accurate way to know the actual volume would be to CC the chambers after the cut.

951and944S

The combustion chamber is not the same size as the cylinder.

Your formula assumes it is.

T

wildcat077

Thanks guys !

Going to bring my head to the machine shop so they can measure it accurately ...

Holytin