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Old 1st October 2007, 22:40   #1
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Post Changing Compression Ratio & Gear Ratio

Hi. I wanted to know if there is any (cost effective) way to change :
1. The compression ratio of an engine
2. Gear ratio of a car.
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Old 1st October 2007, 23:19   #2
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Default compression ratio

The cheapest way to increase the compression ratio is by installing an another head gasket or else you could go overbore the cylinder liners. This would require complete overhaul of the engine.
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Old 2nd October 2007, 00:15   #3
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Quote:
Originally Posted by amitpunjani View Post
The cheapest way to increase the compression ratio is by installing an another head gasket or else you could go overbore the cylinder liners. This would require complete overhaul of the engine.
its not clear whether he wants to increase or decrease his compression ratio. installing another head gasket would only decrease the compression ratio.

shaving the head would effectively increase the compression ratio.

wats all this for anyway?
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Old 2nd October 2007, 00:21   #4
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To increase CR of engine.

1. Shave head.
2. Use high CR pistons.
3. Use longer conrods.
4. Use a thinner head gasket.

To change gear ratios you have to change the gears with different ratios .
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Old 2nd October 2007, 11:54   #5
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To increase compression get a higher deck piston , and to lower get a lower deck piston .
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Old 2nd October 2007, 13:08   #6
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Thanx for the quick response. I would like to increase the compression ratio fRom 7.1:1 to about 9:1. Can it be done just by changing the header gasket ? Also would the changing of gear ratios require the replacement of whole gear box or just some off the gears?
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Old 3rd October 2007, 00:15   #7
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7.1:1 hmmm...is this a Fiat we are talking about? If yes then shaving the head is the way to go. Yes, it is the most cost effective way.
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Old 3rd October 2007, 09:54   #8
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Quote:
Originally Posted by adheesh View Post
Thanx for the quick response. I would like to increase the compression ratio fRom 7.1:1 to about 9:1. Can it be done just by changing the header gasket ? Also would the changing of gear ratios require the replacement of whole gear box or just some off the gears?
Shaving the head as ananth has mentioned. If you can give the dimensions of the pistons maybe someone might be able to recommend some high comp pistons as well.

Changing of gear ratios would include changing of some gears & if need be the final drive and not the entire gearbox.
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