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Thread: How To figure the compression ratio of your Zetec Reply to Thread
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Topic Review (Newest First)
04-12-2013 10:21 PM
sdaddy Big question: relative benefits of a a completely new bottom end?
04-12-2013 10:19 PM
sdaddy
Quote:
Originally Posted by Dgc333 View Post
Absolutely and you need to know the CC's of the head gasket too.
Head was 43cc before .020" was removed and gasket is stock Ford Zetec Blacktop.
04-12-2013 10:14 PM
Dgc333
Quote:
Originally Posted by 1turbofocus View Post
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
Absolutely and you need to know the CC's of the head gasket too.
04-12-2013 08:25 PM
sdaddy Compression measured at 170 psi.... seems low. Perhaps due to overlap with stage II cams??
04-01-2013 09:30 PM
sdaddy Engine is together and running like a scalded cat. Need to finish tuning the Emerald a bit for top end though. Compression gauge ordered.... will report shortly on actual figures.
02-07-2013 08:17 PM
sdaddy
Quote:
Originally Posted by sdaddy View Post
Just had my head cc'd today and it's 46. There's a long story....

Looking at the the great info on this thread, with a stock block, pistons and Ford head gasket (.027" or 0.6858mm), if I have .020 taken off the head the compression ratio will be about 10:3:1, right?
Well, I went with .020" off and will report here how the compression ratio ended up - as measured dynamically.
02-05-2013 09:06 PM
sdaddy Just had my head cc'd today and it's 46. There's a long story....

Looking at the the great info on this thread, with a stock block, pistons and Ford head gasket (.027" or 0.6858mm), if I have .020 taken off the head the compression ratio will be about 10:3:1, right?
11-30-2012 10:07 PM
iminhell Dynamic you mean ...

Multiply the gauge reading by 0.0491.
That will give you an approximate dynamic compression rating.

200 - 9.820
180 - 8.838
160 - 7.856
140 - 6.874
120 - 5.892
100 - 4.910
11-30-2012 07:16 PM
sdaddy Is there a way to determine approximate compression ratio from a static compression reading?
02-16-2012 05:28 PM
iminhell The first section in blue is what compression should hit by 'shaving the head', that is having a machine shop remove material from mating surface of the head to block.

The Red is the same thing but using the standard zetec head gasket.

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






So, by just using the standard zetec head gasket your compression is raised to 10.6:1.

If you want to go 11.5-12:1 you'll have to shave the head (or buy high compression pistons and connecting rods).
So you'll have to shave from 0.0800-0.1270cm (or 0.0315-0.0500in).
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