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Thread: Rough Boost Numbers - Novi 2000 on a 302/351

  1. #31
    SCH Moderator Hustler's Avatar
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  2. #32
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    With a 7.75 crank and a 3.6 blower pulley I was making 11lbs.

    Made a 3.4 blower pulley and it bumped up 2 lbs to 13. Noticed some slight belt slip up in the upper rpm ranger. I am going to assume that once the Novi starts getting up in the 50k+ RPM range that its getting harder to turn and this is with a 10 rib. I think I will switch over to a cog drive.

    Anyhow it made 630 rwhp at 6200 on mustang dyno but I believe those numbers to be very conservative and I will find out Friday what the car runs at the track.

  3. #33
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    I never seen a 347ci getting more than 14-15psi of boost. Is it possible to get more?

  4. #34
    SCH Moderator Hustler's Avatar
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    With the added displacement of the 347, and the assumption that the 347 has aftermarket heads, you will always see less boost than say a 302 because boost is just a measure of restriction. Typically a bigger motor will have bigger ports, displace a larger volume of air through the chamber on each stroke etc. There is no magically number like 17 or 20psi that shows that the supercharger is maxed out. The only way to determine when the supercharger is maxed out for a particular combination is to calculate the impeller speed via the pulley ratio and maximum rpm of the motor.

    Think of it this way, your breath represents a supercharger pullied to its maximum rpm. Blow as hard as you can into a straw using one breath without passing out :). Consider how much effort it takes for you to blow all that air through that tiny straw as you do it. Then go do the same thing using two straws. You will find it takes less effort to blow through two straws than one because you increased the area which you can blow the air through. So one straw equates to a 302, two straws equates to a 347, three straws 408, etc. That effort is equivalent to boost. You are still blowing the same amount of air each time through the various straws, it just gets easier with more straws because there is less restriction in the path of the air. So the supercharger is still pushing the same amount of air through the different engines, it just doesn't have to push as hard on the bigger cubic inch engines. This is the best example I could come up with.
    Last edited by Hustler; 06-24-2010 at 12:25 PM.

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