What compression ratio would I have if...
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Melting Slicks
Joined: Aug 2012
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From: Titusville Florida
Instructor
Joined: Sep 2012
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From: Connellsville PA
Article in the latest Hot Rod Magazine comparing older Chevy heads vs newer heads says the same thing. Going from 76cc to 64cc heads increases compression 1 to 1.5 points all else being the same. Figure 10 to 1 with 64cc heads.
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Drifting
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From: East Wenatchee (2hours from n e where) WA
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Melting Slicks
Joined: Aug 2012
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From: Titusville Florida
Thanks guys, I was looking at an edelbrock combo yesterday that got me at where I want to be HP wise and it said that the compression ratio should be at least 9.5 to get the HP rating with their combo... Thanks again for helping a mathematically challenged old troop 
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Melting Slicks
Joined: Aug 2012
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From: Titusville Florida
Drifting
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From: East Wenatchee (2hours from n e where) WA
Sand Hill 11B
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Melting Slicks
Joined: Aug 2012
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From: Titusville Florida
This is the kit that would get me where I want to be HP wise with that compression ratio.
http://www.jegs.com/i/Edelbrock/350/2098/10002/-1
http://www.jegs.com/i/Edelbrock/350/2098/10002/-1
Race Director
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From: Millington Illinois
St. Jude Donor '08-'09
This is the kit that would get me where I want to be HP wise with that compression ratio.
http://www.jegs.com/i/Edelbrock/350/2098/10002/-1
http://www.jegs.com/i/Edelbrock/350/2098/10002/-1
The advertised duration on that cam is 308/318.
Duration @ .050 is 234/244.
This is a bigger cam than I have in my 10.5 to 1 383 with 6 speed and 4.11 gear and mine as a hydralic roller.
Le Mans Master
Joined: Apr 2011
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From: Hermosa
One thing I can tell you is that advertised numbers are not totally accurate. On my 77 L-48 it was supposed to be 8.0:1 CR engine. In reality it had 17cc dish pistons and 80cc heads that were supposed to be 76cc. The real CR was more like 6.77:1.
So your L-82 probably has more on the order of 7.5:1 to 8.0:1.
I purchased 64cc heads from Dart and they were in reality 67cc's. It's not as easy as you may be led to believe getting the CR up to something acceptable with just a top end.
So plan on using a cam that can support a lower compression ratio. The kit you mentioned may be ok for 9.5:1 at 6000 rpm but I bet it is a dog off the line. To me it looks like a cam for 10.5 or 11.0:1 CR. The RPM air gap intake is also a high rpm intake, not good for low end torque.
Do LOTS of homework before you pull the trigger. You'll be much happier with the results.
So your L-82 probably has more on the order of 7.5:1 to 8.0:1.
I purchased 64cc heads from Dart and they were in reality 67cc's. It's not as easy as you may be led to believe getting the CR up to something acceptable with just a top end.
So plan on using a cam that can support a lower compression ratio. The kit you mentioned may be ok for 9.5:1 at 6000 rpm but I bet it is a dog off the line. To me it looks like a cam for 10.5 or 11.0:1 CR. The RPM air gap intake is also a high rpm intake, not good for low end torque.
Do LOTS of homework before you pull the trigger. You'll be much happier with the results.
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Melting Slicks
Joined: Aug 2012
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From: Titusville Florida
Thank you guys for all your comments, I do appreciate them. While I can put an engine together the math is not what I can do (yes I am a math moron!). I will abandon the idea of a "top end kit" and when the time comes I will look to you guys for help. I would like to get close to 400 HP out of the parts, cam, heads and intake. If I can only get 350 or so then that's what I get...
My current motor is a Jegs (GM), crate motor, they advertise it as 8.5:1 and I have a character flaw in that I tend to take people at their word
The motor is advertised right now as 260 HP with the CR and 76 cc heads but whether any of that is actual I'm thinking your guess is better than mine.
Also, I currently have a 4 spd, will eventually put a 5 spd in it, with 355 gears.
Thanks again all
My current motor is a Jegs (GM), crate motor, they advertise it as 8.5:1 and I have a character flaw in that I tend to take people at their word
The motor is advertised right now as 260 HP with the CR and 76 cc heads but whether any of that is actual I'm thinking your guess is better than mine.Also, I currently have a 4 spd, will eventually put a 5 spd in it, with 355 gears.
Thanks again all