How To figure the compression ratio of your Zetec
I always have trouble trying to find this info and I'm not the best with wanting to do the math. I found a good write up on a different site that I'm working off to give us good info. Here goes ...
The advertised static compression ratio for the US spec Zetec is 9.6:1, note the US spec and that we are not talking about the SVT version of the engine. Typically to find the compression ratio you'd use this formula: http://upload.wikimedia.org/math/3/a...841867f901.png but we don't know all the required information to make that formula work so we'll have to work it backwards. (we don't know the combustion chamber volume) b = cylinder bore (diameter)We know the total engine volume is 1998 Cubic Centimeters but we only need the volume of one cylinder to complete the formula. So we divide 1998 by 4, 1998 / 4 = 499.5 Cubic Centimeters. Now to find the Combustion Chamber volume simply divide the total chamber volume by the compression ratio, 499.5 / 9.6 = 52.03125 Cubic Centimeters. Now remember this is a total chamber volume. That is with any relief in the piston and including the head gasket. We can remove the volume of the head gasket because we know what it is. The standard US spec head gasket thickness for the Zetec is 0.6858 mm thick with a bore of (about) 84.8 mm. That means using the formula for the volume of a cylinder we can figure the volume and eliminate it. Pi (3.14159 for all practicality) times the radius (half the diameter of 84.8 or 42.4 mm) squared times the height (which is our 0.6858 mm). 3.14159 X 4.24^2 X 0.06858 = 3.873281546 cubic centimeters Now we can subtract our head gasket volume from our total volume and are left with the cylinder head volume (roughly), 52.03125  3.873281546 = 48.157968454 cubic centimeters. Now lets run through the SVT version for kicks. The SVT has a static compression ratio of 10.2:1 and uses a head gasket that is 1.0414 millimeters thick, 1998 / 4 = 499.5 499.5 / 10.2 = 48.970588235 3.14159 X 4.24^2 X 0.10414 = 5.8262884378 48.970588235  5.8262884378 = 43.144299798 So now we've found out where the extra compression for the SVT comes from. Now it's time to play with some more numbers and make a chart for gasket swapping and milling the head, but remember these are merely approximations and may not be actual, use caution. Standard Zetec Raise Compression: shaving the head (in cm), standard head gasket (.027" or 0.6858mm) 0.0254  50.596702491  9.872184854 0.0508  49.162154982  10.16025437 0.0762  47.727607473  10.465640883 0.1016  46.293059964  10.789954269 0.1270  44.858512455  11.135010339 SVT Head Raise Compression: shaving the head (in cm), standard SVT head gasket (.041" or 1.0414mm), 0.0254  47.536040727  10.507816645 0.0508  46.101493218  10.834790050 0.0762  44.666945709  11.182765960 0.1016  43.232398200  11.553835105 0.1270  41.797850691  11.950375240 with just using the .027" (standard Zetec) head gasket 0.06858  47.017581344  10.62368556 with Zetec head gasket (.027" or 0.6858mm) 0.0254  45.583033835  10.958024466 0.0508  44.148486326  11.314091186 0.0762  42.713938817  11.694074905 0.1016  41.279391308  12.100469124 0.1270  39.844843799  12.536126444 *Please be advised these are only approximations* I figured the compression ratios by taking the displacement divided by 4 divided by the chamber size. Not sure if that is correct but I'd guess it will get you close. Also being no one has ever CC'd the head while shaving it everything is just a guess. Open to criticism and/ or a better chart/method. 
Even though its a approximation, I need some kind of ideal of my compression ratio in my Zetec built short block w/ 9:1 pistons, SVT head. Nice work.

great info!!!, but i'm not sure its totally right, only reason is i was told my compression was 10.7:1 on a head shaved .060". Not saying ur wrong by any means, more than likely, my tuner is wrong, but it seems logical!

[?].

The biggest factor here is the size of the combustion chamber... the SVT has a smaller CC and thats why it has a higher CR.

Im curious if that math would work the same once pistons , deck height , valve job is done etc , I would think you would need to know CC`s of head , CC`s of deck height , CC`s of pistons
Tom 
^^You would. From the way these numbers are figured all we know is the total combustion chamber volume, that is head, head gasket and piston dish volume combined. If you'd CC the head you could eliminate it and would be left with the volume of the piston alone. Then and only then you could figure in actual compression from a piston change.
BTW, that Performance Hookup vendor has CC specs for all the pistons listed on their site. 
looks good, but it looks like some of your numbers in mm are actually in cm. .040" is about 1.016mm. not 0.1016mm.

^balancing equations. Kicked my arse when I was doing the math and nothing would come out right.

I would edit it and make it sticky status!!!! very good info!!!

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