Blower Boost Vs. tune-up
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Blower Boost Vs. tune-up

  1. #1
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    Default Blower Boost Vs. tune-up

    If I change pulleys, what happens?
    I am currently running a 540 BBC, Dart Pro one heads, 9.4-1 Cr. with a Blower Shop 14-71 driven at 5% under on e85. According to the Blower Shop catalog I should be making about 9.5 lb. of boost. If I swap my current pulleys, the boost should go to about 12 lb. Would that a big change or just some change?
    My question is, should I expect to have to re-jet the Carbs. Also, should the idle speed change and what kind of hp change would be expected? I am currently making around 950 hp.

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  3. #2
    steelcomp was here
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    Quote Originally Posted by jimsplace View Post
    If I change pulleys, what happens?
    I am currently running a 540 BBC, Dart Pro one heads, 9.4-1 Cr. with a Blower Shop 14-71 driven at 5% under on e85. According to the Blower Shop catalog I should be making about 9.5 lb. of boost. If I swap my current pulleys, the boost should go to about 12 lb. Would that a big change or just some change?
    My question is, should I expect to have to re-jet the Carbs. Also, should the idle speed change and what kind of hp change would be expected? I am currently making around 950 hp.
    If your tune up is good now, you shouldn't have to change anything. 2.5lbs of boost could add 50hp. The idle speed may go up a little.
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    Senior Member racinjason65's Avatar
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    I have a 1471 on a 565 and when I swap pulleys I just change fuel and minor idle adjustment is all that's needed.

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    Quote Originally Posted by steelcomp View Post
    If your tune up is good now, you shouldn't have to change anything. 2.5lbs of boost could add 50hp. The idle speed may go up a little.
    I saw a thread that was written a couple of years ago related to this and in the first half of the threads there seemed some consensus that for each 1 lb. of boost there would be about 5-7% increase in power. Does anyone remember that thread?
    I only got through half of it, but that seemed a bit optimistic to me.
    Am I not remembering correctly?

  7. #5
    Senior Member racinjason65's Avatar
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    5-7% is not realistic. On a 1,000 hp motor that would be 50-70 hp per pound of boost. I tried several pulley combos on the dyno, from 10% under and 6 lbs of boost to 16% over and 12.3 lbs of boost. We saw 25-30 hp per pound of boost.

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    I am going to spend more time looking for that thread and read all of it, but the posts so far are more in line with what I would think might be correct.
    Thanks.

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