Twin cooled
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From: san antonio
I believe you are correct; the Twin Cooled HO103 is the only 103 with 10:1 compression; I stand corrected. The addition of liquid cooling allowed the increase in compression and cam timing change which translated to in increase in power but I don't know how the compression increase was developed.
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Club Member
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From: Coal grove ohio 45638
I believe you are correct; the Twin Cooled HO103 is the only 103 with 10:1 compression; I stand corrected. The addition of liquid cooling allowed the increase in compression and cam timing change which translated to in increase in power but I don't know how the compression increase was developed.
HDF Community Team
Joined: Jun 2006
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From: san antonio
Are you sure about that? I would like to see the side by side photos of the 9.7:1 and 10.0:. Not doubting what you say but adding to the production cost of a cylinder head to gain a .3 increase in compression is inconsistent with the HD approach to cost and production. The early SE Performance heads were milled .050" with no change to the chamber shape.
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Club Member
Joined: Aug 2017
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From: Coal grove ohio 45638
Are you sure about that? I would like to see the side by side photos of the 9.7:1 and 10.0:. Not doubting what you say but adding to the production cost of a cylinder head to gain a .3 increase in compression is inconsistent with the HD approach to cost and production. The early SE Performance heads were milled .050" with no change to the chamber shape.
Thread Starter
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Club Member
Joined: Aug 2017
Posts: 573
Likes: 43
From: Coal grove ohio 45638
Are you sure about that? I would like to see the side by side photos of the 9.7:1 and 10.0:. Not doubting what you say but adding to the production cost of a cylinder head to gain a .3 increase in compression is inconsistent with the HD approach to cost and production. The early SE Performance heads were milled .050" with no change to the chamber shape.
Thread Starter
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Club Member
Joined: Aug 2017
Posts: 573
Likes: 43
From: Coal grove ohio 45638
Are you sure about that? I would like to see the side by side photos of the 9.7:1 and 10.0:. Not doubting what you say but adding to the production cost of a cylinder head to gain a .3 increase in compression is inconsistent with the HD approach to cost and production. The early SE Performance heads were milled .050" with no change to the chamber shape.
HDF Community Team
Joined: Jun 2006
Posts: 12,774
Likes: 2,606
From: san antonio
Thanks for the photos. I didn't think about the possibility that the liquid cooling was driving the chamber configuration but that makes total sense. No way would the MoCo change the chamber configuration for reducing chamber volume by 2cc but the liquid cooling forced the change.
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Club Member
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From: Coal grove ohio 45638
Thanks for the photos. I didn't think about the possibility that the liquid cooling was driving the chamber configuration but that makes total sense. No way would the MoCo change the chamber configuration for reducing chamber volume by 2cc but the liquid cooling forced the change.
HDF Community Team
Joined: Jun 2006
Posts: 12,774
Likes: 2,606
From: san antonio
If you are talking "wet head" at 10:1 but replacing the OEM head gasket with a .030" head gasket with a set of Andrews 57 cams CCP will be about 200psi and corrected compression about 9.6. That is about as far as I would go with that cam but others may disagree.