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Thread: blower pulley question

  1. #1
    steelcomp
    What's the difference between 8mm and 16mm pulleys, and what are the pro's and con's regarding each? What is ther preferred set up or is there such a thing?
    Thanks :coffeycup

  2. #2
    Fiat48
    I don't know of a 16mm setup and neither did RCD so I can only assume you meant 14mm or I am behind the times which would not surprise me.
    The old 1/2 pitch stuff started having belt problems at about 25% over. So then came the 8mm and that solved that. Then came the 13.9 and the 14mm stuff for these really tight blowers and the ultra rpm. And now there's this 8mm GT pulley the fuel guys have gone to.
    Bottom line...1/2 inch pitch has it's limitations. 8mm has always been my choice. It's all you need and offers a better choice in fine tuning the drive percentage. 1 tooth difference is 2% drive (or very close) so it's easy to figure and more % changes available using the same blower belt. But any of them work.

  3. #3
    steelcomp
    No...you're not behind...I'm stupid. Just wasn't thinking. 8mm vs. 14mm. So it is about the pitch. I thought so. I was told that it had to do with the offset of the pulley(s). (in their defense, by someone who wasn't sure either.)
    So how is the offset issue adressed? What determins what offset you use? The blower I bought has the top pulley, but I have no crank hub or lower pulley yet. The idler comes with the blower as well, so I'm guessing that I'll have to go with what's there.
    Thanks again. :coffeycup

  4. #4
    Fiat48
    Yes..that is all pitch.
    Alignment. They make different blower snouts in length. It goes back to the old wars of Crager and Wiend and where they located the blower on the manifold.
    Long snouts to dodge a car water pump or for blowers set way back. But I think you got a BDS manifold and that is going to take a short snout (6" as I remember), the idler pulley will have a spacer or be made for some adjustments and then on the crank snout you generally have to build your own spacer behind it (varies but maybe .200). Bottom line is you want to be able to straight edge it all when you get done. Some guys just live with the bottom not spaced out but then they kick blower belts once in a while or chaff edges of belts.

  5. #5
    steelcomp
    Yes..that is all pitch.
    Alignment. They make different blower snouts in length. It goes back to the old wars of Crager and Wiend and where they located the blower on the manifold.
    Long snouts to dodge a car water pump or for blowers set way back. But I think you got a BDS manifold and that is going to take a short snout (6" as I remember), the idler pulley will have a spacer or be made for some adjustments and then on the crank snout you generally have to build your own spacer behind it (varies but maybe .200). Bottom line is you want to be able to straight edge it all when you get done. Some guys just live with the bottom not spaced out but then they kick blower belts once in a while or chaff edges of belts.
    OK...I get it. Blower, pulley, intake, idler all came off the same BB Chev, so it's as I thought. Common sense.
    Thanks. :coffeycup
    Wanted...bottom hub and pulley!!

  6. #6
    Fiat48
    Not that easy.
    I got a 500 tooth bottom pulley...you want it?
    Buy a standard blower crank hub. If internal balanced. If external balance, then they make one for that also. Then get all your stuff mocked on.
    Get your mock up done...then refer to chart. http://www.goodvibesracing.com/Engin...lt%20Chart.htm
    Match your belt, blower manifold, engine etc with the chart. The chart is ballpark of what pulleys you can use (total teeth). But applications vary...deck height, etc.

  7. #7
    steelcomp
    OOOOhhhh...I know it's not THAT simple. Right now I have a BDS 14mm 36t pulley on top. I may switch it out and just start over with 8mm, since that seems to be the way guys are going. Internal balance. Neutral hub. Looking for 14-15 lbs to start. Don't know what the overdrive will be for that. I'll look at the charts to see. So much to learn...so little time!!!

  8. #8
    Fiat48
    10 lbs boost at sea level on a 496 with 11.5 to1 compression can make 1050 hp and change at 6500 rpm at 100% ve. Try 10% over if a loose blower to start. Cherry tight blower try about 6 over. The above numbers were for gasoline so add whatever for alcohol.

  9. #9
    steelcomp
    Thank you, thank you. I see an assortment of pulleys in my future! :redface:

  10. #10
    78Eliminator
    Fiat, I think blowers are going away soon. I have seen too many dyno results for NA motors that are making 130%VE. Blowers are a thing of the past..... :notam: :devil:

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