My turn, Compression ratio
Thread Starter
Melting Slicks
Joined: Jun 2012
Posts: 3,163
Likes: 6
From: Oceanside California
My turn, Compression ratio
I was doing the math for my set up and wanted to verify that it is correct.
These are the figures I used
Boar: 3.898
Stroke: 3.622
GT: .045"
DC: -.006"
CCV: 62cc
V1= 43.22380671
V2= 0.53701582
V3= -0.071602109 (minus this number for totals. Protrudes out of boar)
V4= 3.78348691
Totals:
47.47270733
Divided by
4.248900621 =
11.17:1 compression ratio.
Also I want to know what is a safe ratio for 91 octane. If I go thinner on the gasket or mill the heads lover to 60cc and up the compression to 11.5ish:1 will that be ok?
These are the figures I used
Boar: 3.898
Stroke: 3.622
GT: .045"
DC: -.006"
CCV: 62cc
V1= 43.22380671
V2= 0.53701582
V3= -0.071602109 (minus this number for totals. Protrudes out of boar)
V4= 3.78348691
Totals:
47.47270733
Divided by
4.248900621 =
11.17:1 compression ratio.
Also I want to know what is a safe ratio for 91 octane. If I go thinner on the gasket or mill the heads lover to 60cc and up the compression to 11.5ish:1 will that be ok?
Thread Starter
Melting Slicks
Joined: Jun 2012
Posts: 3,163
Likes: 6
From: Oceanside California
Burning Brakes
Joined: Sep 2009
Posts: 1,239
Likes: 2
From: Naples FL
St. Jude Donor '12
You didn't provide the bore size of the gasket, and that does make a small difference. I used 4" for the bore size and came up with 11.11
I'm assuming since your in Cali you have to run a fairly small cam, this and the lower octane reduces the CR you can use. As you know it's the dynamic CR that matters.
I'm not an expert, but I'd personally limit it to the 11:1 range, 11.1 may still be ok. Jegs has a pretty good assortment of gaskets in stock.
I'm assuming since your in Cali you have to run a fairly small cam, this and the lower octane reduces the CR you can use. As you know it's the dynamic CR that matters.
I'm not an expert, but I'd personally limit it to the 11:1 range, 11.1 may still be ok. Jegs has a pretty good assortment of gaskets in stock.
Thread Starter
Melting Slicks
Joined: Jun 2012
Posts: 3,163
Likes: 6
From: Oceanside California
You didn't provide the bore size of the gasket, and that does make a small difference. I used 4" for the bore size and came up with 11.11
I'm assuming since your in Cali you have to run a fairly small cam, this and the lower octane reduces the CR you can use. As you know it's the dynamic CR that matters.
I'm not an expert, but I'd personally limit it to the 11:1 range, 11.1 may still be ok. Jegs has a pretty good assortment of gaskets in stock.
I'm assuming since your in Cali you have to run a fairly small cam, this and the lower octane reduces the CR you can use. As you know it's the dynamic CR that matters.
I'm not an expert, but I'd personally limit it to the 11:1 range, 11.1 may still be ok. Jegs has a pretty good assortment of gaskets in stock.
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Melting Slicks
Joined: Sep 2003
Posts: 2,458
Likes: 105
From: Northville Michigan
Keith Black and United Engine and Machine Company offer a very good web site for calculating your compression ratio:
http://www.kb-silvolite.com/calc.php?action=comp
Fill in the blanks.
You can also calculate your Dynamic Compression Ratio with this form. Plug in your camshaft's intake closing timing.
Good Luck
http://www.kb-silvolite.com/calc.php?action=comp
Fill in the blanks.
You can also calculate your Dynamic Compression Ratio with this form. Plug in your camshaft's intake closing timing.
Good Luck
Last edited by Pumba; Sep 17, 2012 at 08:17 AM.
Burning Brakes
Joined: Sep 2009
Posts: 1,239
Likes: 2
From: Naples FL
St. Jude Donor '12
That would probably explain the .06 difference between our calculations.
Thread Starter
Melting Slicks
Joined: Jun 2012
Posts: 3,163
Likes: 6
From: Oceanside California
If I keep everything the same and use a .050" head gasket, it will put me at 11.03:1. Give or take a few thousands from minor differences, it is basically 11:1. This setup should be good for 91 octane correct?