Cylinder Head cc's VS compression ratio
Thread Starter
Joined: Jun 2005
Posts: 2,265
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From: Oskaloosa, Iowa
Cylinder Head cc's VS compression ratio How much does a single cc of cylinder head combustion chamber size change compression ratio? If I have 11.4 to 1 compression now with untouched AFR heads with 66cc combustion chambers what would my compression ratio be with 72cc heads?
10.6 is my best guess using calculator supplied here
http://www.rbracing-rsr.com/compstaticcalc.html
http://www.rbracing-rsr.com/compstaticcalc.html
There is more you need to know to be exact with the compression.
The one you know is the head.
Next you need to know the thickness of the head gasket
The piston weather it's a dome/ flattop/ or a dished piston.
Then you need to know how far down or how far up the piston sits in the hole or out of the hole.
The one you know is the head.
Next you need to know the thickness of the head gasket
The piston weather it's a dome/ flattop/ or a dished piston.
Then you need to know how far down or how far up the piston sits in the hole or out of the hole.
Thread Starter
Joined: Jun 2005
Posts: 2,265
Likes: 671
From: Oskaloosa, Iowa
The engine builder told me it was 11.4 to 1. I have a 408 that is a 4.030 bore 4.0 stroke, pistons have 2cc valve reliefs, heads have 66cc chambers, and GM head gaskets. My original plan was to run NA the first year which I did and then run nitrous my second year which I'm now considering. I was just wondering if 72cc heads would get my compression ratio low enough to run say 7 pounds of boost. I just want to consider all my options before I make my next step. I also change my mind alot...lol
using that info and .052 for the gm gasket piston .007 out of the hole I came up with 11.8. With the piston level(not out) I came up with 11.6. 66cc heads
11.02 with piston out of hole .007 and 10.85 level with deck. 72cc heads
moving your calculations to 11.4 with 66 heads ...then upping the cc's to 72 I come up with 10.68
11.02 with piston out of hole .007 and 10.85 level with deck. 72cc heads
moving your calculations to 11.4 with 66 heads ...then upping the cc's to 72 I come up with 10.68
Thread Starter
Joined: Jun 2005
Posts: 2,265
Likes: 671
From: Oskaloosa, Iowa
Originally Posted by The stunningman
using that info and .052 for the gm gasket piston .007 out of the hole I came up with 11.8. With the piston level(not out) I came up with 11.6. 66cc heads
11.02 with piston out of hole .007 and 10.85 level with deck. 72cc heads
moving your calculations to 11.4 with 66 heads ...then upping the cc's to 72 I come up with 10.68
11.02 with piston out of hole .007 and 10.85 level with deck. 72cc heads
moving your calculations to 11.4 with 66 heads ...then upping the cc's to 72 I come up with 10.68
