 Hitting the exact Compression Ratio |
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| malcolm2 |
 Nov 28 2011, 12:42 PM
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Advanced Member  Group: Members Posts: 2,747 Joined: 31-May 11 From: Nashville Member No.: 13,139 Region Association: South East States 
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I am to the point on my rebuild that I need to make a decision. (IMG:style_emoticons/default/confused24.gif)
I am sure that this type of discussion can become very technical and fill volumes of books. I am not asking for that. I am the kind of person that wants to know "why" a certain cam needs a certain CR. In order to make the best decision, I need answers. Or if it is a huge secret, that is fine too. I can go blindly along with the crowd. Maybe it's really what. Has anyone experienced What an engine will do, or what will I see or feel if my cam mfg recommends 8.0:1 CR and my normal state (no shims) is 8.35:1 CR? To get to just about 8, I have calculated that I need about 2mm of deck height. I am currently sitting at 1.62mm average DH with a variance between cylinders of 0.15mm. So I need two 0.4mm shims and two 0.5mm shims and I will be dead nuts on 8:1. (IMG:style_emoticons/default/stirthepot.gif) So the mfgr's value can be reached (if I can round up the shims), but I am curious to know how differently the engine will function if I go shim-less or even only get half way, maybe 8.2:1. (IMG:style_emoticons/default/WTF.gif) |
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| Jake Raby |
Nov 28 2011, 03:26 PM
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Engine Surgeon Group: Members Posts: 9,398 Joined: 31-August 03 From: Lost Member No.: 1,095 Region Association: South East States |
It is common to achieve different true deck heights on opposite sides of the engine. It is generally a .005-.007 differential from the 1-2 bank to the 3-4 bank with 3-4 always being tighter.
The cam that he is running was developed and tested with a maximum and minimum compression ratio. It doesn't mean that he is being forced to run this CR. It simply means that the stories about how awesome this cam has worked for others that he may have read might not be applicable to him. (people wonder why I stopped recommending anything to anyone under any circumstance) |
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Posts in this topic
malcolm2 Hitting the exact Compression Ratio Nov 28 2011, 12:42 PM
McMark Don't mix different height shims on the same s... Nov 28 2011, 12:52 PM
malcolm2
Don't mix different height shims on the same ... Nov 28 2011, 02:46 PM mark21742 Most cam manufacturers give you minimum compressio... Nov 28 2011, 01:08 PM r_towle Compression ratio and camshaft selection go hand i... Nov 28 2011, 01:17 PM malcolm2
Compression ratio and camshaft selection go hand ... Nov 28 2011, 02:43 PM Marty Yeoman
You have other options if you do not want to shi... Nov 28 2011, 02:51 PM malcolm2
You have other options if you do not want to sh... Nov 28 2011, 03:01 PM r_towle Jake Raby
or
European Motorworks
rich Nov 28 2011, 02:46 PM r_towle more deck height is either more shims or deeper ch... Nov 28 2011, 03:07 PM malcolm2
more deck height is either more shims or deeper c... Nov 28 2011, 03:14 PM r_towle if you had the case "checked over" they ... Nov 28 2011, 03:21 PM malcolm2
It is common to achieve different true deck heigh... Nov 28 2011, 03:49 PM Jake Raby
I am trying really hard to lessen that expectati... Nov 28 2011, 04:13 PM malcolm2
I am trying really hard to lessen that expectat... Nov 28 2011, 07:28 PM |
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