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How to work out a comp ratio 

 

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 Post subject: Re: How to work out a comp ratio
Posted: Wed May 11, 2011 8:09 pm 
Getting Side Ways
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ausedwagon wrote:
Longer rods could do it


HOW?



It times like these you need FACE PALM.

 

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 Post subject: Re: How to work out a comp ratio
Posted: Wed May 11, 2011 8:26 pm 
Getting Side Ways
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A longer rod, with no change in piston, will reduce the space above the piston both at BDC and TDC - effectively bringing the piston closer to the head, rather than the head closer to the piston. A .010" longer rod has the same effect on compression as a .010" thinner head gasket or block skim.

You then have the issues of piston-to-head clearance and rod-to-block clearance. And is such a rod actually available? If the next step up is .500" longer, that would put the piston clean through the head, so it's not a solution. Probably easier and cheaper to go for high compression pistons and a head skim, per tickford_6.

 

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 Post subject: Re: How to work out a comp ratio
Posted: Wed May 11, 2011 10:22 pm 
Getting Side Ways
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efxr6wagon wrote:
A longer rod, with no change in piston, will reduce the space above the piston both at BDC and TDC - effectively bringing the piston closer to the head, rather than the head closer to the piston. A .010" longer rod has the same effect on compression as a .010" thinner head gasket or block skim.

You then have the issues of piston-to-head clearance and rod-to-block clearance. And is such a rod actually available? If the next step up is .500" longer, that would put the piston clean through the head, so it's not a solution. Probably easier and cheaper to go for high compression pistons and a head skim, per tickford_6.



10 thou longer rod is a very costly way to deck the block 10 thou. The only up side to it is you are saving 0.5mm in timing chain slack, which is minimal and not worth worrying about.
Even if you could buy them, they aren't going to be of any real help in getting the compression the OP was asking about. The money would be better spent on a set of pitons with a dome that matches the shape of the chamber.

 

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 Post subject: Re: How to work out a comp ratio
Posted: Wed May 11, 2011 10:35 pm 
Parts Gopher
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Well i ask atomic performance about some pistons they told me about 1800$ for some to be made up.. but i was thinking going acl not to sure on the price on these and i say it would be a better option?

 

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