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Old 09-05-2007, 03:00 PM   #1
rpm_nick
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Default compression ratio question

I am gathering the last parts of my build and would like opinions on CR. Here are the parts.

2.2 N/A block .020 over
USDM wrx heads
Wiseco 2.2l turbo pistons
2.2 rods and crank
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Old 09-05-2007, 07:00 PM   #2
rustyzipper
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8.5 or 9.1 , your choice, depends on what you want to do with it.
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Old 09-06-2007, 12:04 AM   #3
Kosmic
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There is a few CR calculator links in that thread. echo?

http://forums.nasioc.com/forums/show...hlight=genious
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Old 09-06-2007, 03:41 PM   #4
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looking for reliability for a daily.
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Old 09-06-2007, 03:51 PM   #5
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which piston (need model number)? what headgasket (thickness and bore)? and how much are you decking the block?
all things that you need to know to figure out what CR you'll have.
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Old 09-06-2007, 04:47 PM   #6
rpm_nick
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I know how to come up with the compression ratio. I am trying to decide on what to go for. All the machine work is done it is just down to figuring the head gasket to use and if I need to deck the block. I was leaning towards 8.5:1 for the CR. Just trying to get others opinions on the matter.
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Old 09-06-2007, 04:55 PM   #7
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do you have water/alky injection? If so, I'd say 9:1
If not, I'd say 8.5:1
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Old 09-07-2007, 01:37 PM   #8
rpm_nick
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Nope just building a "stock" setup for the most parts, nothing major done to it. From my calculations if I run the .030 cometic I will be sitting at 8.36:1. If I have clearance for the .027 it will up it to 8.41, just need to check valve clearances.
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Old 09-08-2007, 12:24 AM   #9
hotrod
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you don't want to deck the block that jacks up your cam timing due to its effects on the cam drive belt length between the crank nose and the cams. It changes the cam timing more on one head than it does the other so it makes for problems you don't want to deal with.

There are a couple posts on this where folks ran into that problem.
There is a very small limit to acceptable change in head gasket thickness, and deck height, cylinder head milling must all fall within.

Larry
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Old 09-09-2007, 01:14 AM   #10
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you can deck the block and head but make sure that you deck the right amount and use the right headgasket to offest the amount you removed and set you back to zero...then no cam timing gets affected
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