How To Adjust A Blower Belt
When running a Roots type blower (BDS, Weiand, Blower Shop, 6-71, 8-71, 10-71, 12-71, etc,) and you have either a 1/2" pitch, an 8mm rib, or even a 14mm rib drive belt, the object of a blower belt not slipping isn't "tension" like a normal V or serpentine belts because blower belts rely on the "teeth" or cogs of the belt to prevent slippage.
What's hard on a blower, as well as a crank snout, the front main bearing, as well as the blower drive bearings, is a belt that's too tight. You'd be surprised how much a blower "grows" when it gets hot and all of that aluminum expands. It can take a belt that has an inch or so of play in it when it's cold and make it tight as a drum when it's hot, which as I just said, is really hard on things.
Some people say to adjust the belt so it has half a "twist" of "slop" in it when cold. My trick is to just run it loose, then let the engine warm-up and THEN adjust the belt after the engine has gotten to full operating temperature and that blower, manifold, etc, have all expanded to their hot running size, THEN adjust the belt so it has no slop, but isn't "tight". Wherever it ends up when it's cold is just where it's going to be.
You aren't running the engine cold, or at least not hard when it's cold, so don't worry about it. Doing it this way takes-out all of the guess work out as to how loose the belt needs to be when everything is cold, or how much the blower might, or might not, expand once it's hot. Just do the adjustment when it's hot and take all of the guess work out of it and you'll be good to go. Remember, not tight... just enough tension so it isn't slopping around once it's hot. It ain't a V or serpentine belt o don't treat it like one.
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