Hey everyone. I just bought a 6-71 blower and I had a few questions about the engine set up. I plan on running around 6 lbs of boost, but under 10lbs for sure. I'm running a 283 I planned on running forged pistons but would hypereutectic pistons be alright? Is there a good compression to shoot for? I know It should be low, but how low? Whats the lowest but the safest CFM I could run? Thanks alot! Dylan
I'd use forged pistons, just because. You could probably get away with hypers, or even cast, but how long do you want the thing to last? are you sure your boost will always stay low? 1000 cfm should be plenty, maybe a pair of old Carter 500s? 7.5:1 to 8:1 is probably ideal, allows you to make lots of power using the boost, and lets you run cheap gas (I run 87 in my blown 454 with 7.5:1 and 7 psi)
Street only. I plan on driving it often. Yeah I suppose, I should just run forged. Are you running a 6-71? What was your drive ratio(top pulley to bottom pulley)? What was the power increase? Is there a calc for what the compression will hop up to at 6 lbs of boost? Thanks for the help. Dylan
NO! First of all, the "boost" is only a measurement of manifold pressure, not air flow through the heads. Secondly, an increase in manifold pressure does not necessarily indicate an increase in air flow through the heads (the air the blower is moving might begin stacking up in the manifold in a constipated engine). There are way too many variables to try to make a direct correlation between a specific manifold pressure and a specific cylinder pressure.
I'm running a 6-71 on a much larger engine, pulleys are only one tooth different. For a little 283 you'd have to run way underdriven to keep boost down that low, a 4-71 is better suited. here are some charts, fwiw http://www.blowerdriveservice.com/techcharts.php
BDS uses this chart for compression ratio under boost. http://www.goodvibesracing.com/Compression%20Ratio.htm Mutt
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