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Compression Ratio

Old 09-18-2010 | 05:28 PM
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Default Compression Ratio

How much power will I gain going from 9:00 to 1 up to 10:00 to 1:00 compression?

The motor is a 502 standard bore & stroke, full port job on heads, block zero decked and squared, tuned exhaust, 741 cam.

Just trying to get an idea......or should I just slap a blower on ?
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Old 09-18-2010 | 06:14 PM
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The 502's are good canidates for a blower, I would just put a small blower on it like a B&M 250 there are a couple in the swap shop right now. The cost of redoing your engines or putting a nice used blower on it would be about the same and you would get more hp for your dollar.

http://www.offshoreonly.com/forums/s...-ready-go.html

http://www.offshoreonly.com/forums/s...-complete.html

I know both of the guy's selling those blowers they are stand up guy's.

Last edited by Velocity Vector; 09-18-2010 at 06:27 PM.
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Old 09-18-2010 | 10:04 PM
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I am running 509's with the same cam but I have Jim V ported Pro 1's , Lightning headers,Dart intakes, Dooley 10 Qt oil pans and HP 950 Holley's.
I am running 10 to 1 CR but the pistons are zero decked for good quench. 650 HP...

Last edited by Tinkerer; 09-18-2010 at 10:07 PM.
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Old 09-19-2010 | 07:16 PM
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Originally Posted by Tinkerer
I am running 509's with the same cam but I have Jim V ported Pro 1's , Lightning headers,Dart intakes, Dooley 10 Qt oil pans and HP 950 Holley's.
I am running 10 to 1 CR but the pistons are zero decked for good quench. 650 HP...
Just curious, how fast does a 34' Scarab go with 1300 HP? I had an 83' Scarab III with TRS drives and @ 1000 HP and the best it could do was 69.6 MPH on GPS.
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Old 09-19-2010 | 07:22 PM
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Oops, forgot to provide a response to the original post. In the 90s I built a pair of 10-1 engines and the common belief at that time was 1 point of compression on a BBC was worth 4-5% in horsepower and a little more torque. They will require 93 octane, the same as a mild boost blower set up and will not make as much power. Go with boost...
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Old 09-19-2010 | 08:16 PM
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Because of the tight quench I can run midgrade with no knock.
The 91- 93 34 Scarab is faster with the same HP than the older Scarab III.
I have GPS'd at 84 MPH in ideal conditions.
I can run 80 on flat water anytime.
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