will a large cam affect compresion??
06-25-2002, 11:32 PM
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will a large cam affect compresion?? What I was wondering was that if i have stock heads with headers and bolt ons and run say a TR 230/224 will it lower the compression any? <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" /> Also there will be the use of 918's. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
P.S. i beleive that the TR230 is a 111lsa <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
<small>[ June 25, 2002, 11:35 PM: Message edited by: Sparkyls1 ]</small>
P.S. i beleive that the TR230 is a 111lsa <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
<small>[ June 25, 2002, 11:35 PM: Message edited by: Sparkyls1 ]</small>
06-25-2002, 11:35 PM
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Re: will a large cam affect compresion?? Yes, It will drop slightly I recommend a good stall to make up for the lost low end power.. <img border="0" alt="[Fluffy]" title="" src="graemlins/fluffy.gif" />
06-25-2002, 11:45 PM
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Re: will a large cam affect compresion?? ANYONE else got input? This is the same guy i have already spoken to about this any other veiws? <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />
i.e. personal experience WITH THE LS1 doing this
i.e. personal experience WITH THE LS1 doing this
06-26-2002, 06:49 AM
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Re: will a large cam affect compresion?? Headers and boltons won't affect your compression ratio. I can't say for sure what exact effects that cam would have unless I saw a graph of the duration curves along with the overlap on that 111LSA cam (obviously a higher LSA would have a higher compression). That seems like a lot of intake duration though...
06-26-2002, 11:27 PM
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Re: will a large cam affect compresion?? Hi,
A big cam holds the intake valve open longer which lowers the cranking pressure. The CR is raised with big cams to recover the cranking pressure.
There are two compression ratios to track. The geometric CR is what is normally called CR. It is based on the engine geometry only. The effective CR is based on the trapped volume after the intake closes. It will always be lower than the geometric CR. The cranking pressure is an indication of the effective compression ratio.
Based on the geometry of the LS1, to hold the effective CR constant as the intake valve is held open longer, the geometric CR would look like this:
IVC CR
60 9.87
65 10.26
70 10.70
75 11.23
Good luck,
Steve
A big cam holds the intake valve open longer which lowers the cranking pressure. The CR is raised with big cams to recover the cranking pressure.
There are two compression ratios to track. The geometric CR is what is normally called CR. It is based on the engine geometry only. The effective CR is based on the trapped volume after the intake closes. It will always be lower than the geometric CR. The cranking pressure is an indication of the effective compression ratio.
Based on the geometry of the LS1, to hold the effective CR constant as the intake valve is held open longer, the geometric CR would look like this:
IVC CR
60 9.87
65 10.26
70 10.70
75 11.23
Good luck,
Steve