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Old 09-03-2009, 12:15 PM
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Still more blower questions

I started a new thread as this is not about the carb.

BDS tell me that the stock harmonic balancer is not to be used with a blower as it will break. They tell me to use their hub or an aftermarket balancer that states that it's for a blower. Which one would that be?

We are going to be underdriven and always on the street, is it so?

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Old 09-03-2009, 01:41 PM
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they usually recommend a steel hub or steel damper as they are less prone to fracture from the harmonics and stress added by the gilmer belt and adtnl. drag from the blower drive. you can do a search on this site for damper opinions for whats best. I ran a 671 on a sbc for 6 years on the street/underdriven with a stock balancer, but back then it was: a hub that was not a harmonic balancer, or a factory balancer,as there weren't any aftermarket dampers
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Old 09-03-2009, 03:13 PM
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Also, hubs and balancers meant for blower use will have a second keyway in them 180 from the factory keyway. It is usually a larger size keyway to take more load, using just the factory stock key will end up shearing it off, tearing up the crank snout and possibly throwing the balancer.

If you don't already know this, you have to get the crankshaft nose cut for this second key also.
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Old 09-03-2009, 03:46 PM
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Because this is more of a ENGINE question ... As Moderator, I am moving it to the ENGINE area where perhaps better informed engine folks might see the question and the answers MAY HELP others interested in supercharging their engine.

Deuce ... Moderator
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Old 09-03-2009, 05:33 PM
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You don't need a harmonic damper on the crank if you run a Roots type blower with the toothed Gilmer belt. The belt absorbs harmonics and protects the crank from cracking just like a harmonic damper would. Use a solid hub and you'll be fine.

Just to clarify, on all small block Chevies up through 350, the unit is correctly identified as a harmonic damper, not a balancer. On a 400 small block, it is a harmonic damper/balancer.
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