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Old 12-06-2012, 06:40 PM
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Originally Posted by cdminter59 View Post
Using United Engine & Machine Co. Incorporated your Static Compression is 9.199 and your DCR is 7.128. If you ever want to bump up your compression all you have to do is use the .015 steel shim head gasket. This will give you 9.664 and 7.476.
Using 9.2:1 SCR and an intake closing point of 32 degrees ABDC plus 15 for the calculator, DCR would be 8.262:1 and should make good power and work really well on pump gas.
I have no idea what intake closing point you used, but on Comp Cams, the intake closing at 0.050" is not published. You have to figure it yourself from the 0.050" duration and the intake centerline.
12-234-2 - XTREME Energy

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Old 12-07-2012, 07:41 AM
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comp ratio

Here is the specifications on the Comp Cams XE256H. 12-234-2 - XTREME Energy You are right the intake valve closing is 32* at .050". Not paying attention I used the valve opening at 6*

Last edited by cdminter59; 12-07-2012 at 07:56 AM.
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Old 12-07-2012, 12:22 PM
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Originally Posted by smith9300 View Post
Ok I used a cr tester and on my engine it said it had 9.1 to 9.2 that is off Fromm what everybody kept telling me just wondering what ppl think and if it is around what I said what kind of gas would I have to run thanks to any
I ran this through my Excel based SCR and DCR calculator getting 9.19 Static and 8.055 Dynamic.

Feed data some assumed

- 400 inch stock bottom end
- 4.125 bore
- 3.75 stroke
- 5.56 rod
- Deck clearance .025
- Head gasket .039 compressed
- Piston dished 22 ccs
- Head Vortec 64 ccs
- Cam XE256H intake closed at 55 degrees ABDC, Intake at .050 inch 47 degrees after ABDC, calculation used is based on average Hydraulic Intensity calcuated for when intake is still open at .006 above the seat as 52.2 degrees ABDC, the apparent stroke is 3.23 inch.

Looking at this from a cam data distribution stand point

When intake is closing at .050 above the seat event is 47 degrees ABDC this would make a stroke length of 3.325 with a DCR of 8.26 to 1.

When intake is fully closed the seat event is 55 degrees ABDC this would make a stroke length of 3.168 with a DCR of 7.919 to 1.

A Vortec head can take a little more compression even on the larger 400 bore, as was previously stated by hcompton this can be boosted a bit with a thinner head gasket where a .015 gasket would boost the SCR to 9.66 with the DCR running in the ranges I calculated of 8.317 when closed, 8.44 at .006 off the seat, at .050 the DCR would be 8.68. So simply changing the assumed .039 composition head gasket to a shim styleis good for nearly a .5 to 1 increase in the DCR.

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Old 12-09-2012, 06:46 PM
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Would doing that increse my power noticeably
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