Compression Ratio calculations
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Posting Guru
Joined: Mar 2006
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From: Williamson, NY
Compression ratio ?
I was trying to estimate my compression ratio for a 302 engine I am rebuilding using the calculator I found here on this site at: https://www.ford-trucks.com/lc/lc.php?action=do&link=http%3A%2F%2Fraceabilene.com %2Fkelly%2Fhotrod%2Fengine.html and some of the values asked for I had to guess at and I was wondering how good my guesses were. The ones I guessed at were:
- Compressed head gasket thickness....I estimated it at 1/16" or 0.0625"
- Head gasket bore diameter...............I estimated it at 4.060"
- Piston to deck clearance..................estimated it at 1/8" or 0.125"
- Piston reliefs ( I have flat tops w/ 4 reliefs) and I estimated the volume at
0.35cc's.
The calculator said my displacement was 3.06 w/ 0.030" + pistons and my compression ratio @ 7.16 using my above estimates.
Any input on my estimates? Thanks.
Jim
- Compressed head gasket thickness....I estimated it at 1/16" or 0.0625"
- Head gasket bore diameter...............I estimated it at 4.060"
- Piston to deck clearance..................estimated it at 1/8" or 0.125"
- Piston reliefs ( I have flat tops w/ 4 reliefs) and I estimated the volume at
0.35cc's.
The calculator said my displacement was 3.06 w/ 0.030" + pistons and my compression ratio @ 7.16 using my above estimates.
Any input on my estimates? Thanks.
Jim
Last edited by TigerDan; Apr 13, 2006 at 11:53 PM.
Elder User
Joined: May 2005
Posts: 537
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From: Graves County, KY
I came up with 7.65:1 for your combo (with ken's gasket thickness). That seems corrcect if your piston to deck clearance really is .125. That's what's keeping your ratio low.
I don't know what comp ratio you're looking for, but a .025 deck would give you 9.55:1
*EDIT* I did this with 59cc heads. 65cc heads would be 8.90:1
I don't know what comp ratio you're looking for, but a .025 deck would give you 9.55:1
*EDIT* I did this with 59cc heads. 65cc heads would be 8.90:1
Last edited by wintremute; Apr 14, 2006 at 08:23 AM.
