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drive sheave fit

Discussion in 'Fisher Engineering Discussion' started by Megunticook, Nov 2, 2008.

  1. Megunticook

    Megunticook Senior Member
    from Maine
    Messages: 190

    I run an older belt-drive system on a Dodge pickup with a 318 motor. Went to install a new drive sheave today (part #7748), which bolts onto the harmonic balancer on the crank (over the factory pulley).

    Much to my surprise, the pulley wouldn't seat properly in the female recessed hole in the center of the harmonic balancer (where the factory washer and center bolt were seated before being removed).

    Checking with my caliper, I found the male portion of the drive sheave measures 1.535" while the female hole in the harmonic balancer is 1.5.

    I double checked the part number and it's correct. Brand new, direct from Fisher.

    What gives? Why would a part like that be machined to 1 17/32" (approximately, it's actually a little bigger)? This must be a manufacturing error, right?

    Is there an easy way to safely remove a little material from the drive sheave? Only needs to be 1/64" all around. Would coarse Emery cloth do it?
  2. wirenut

    wirenut Senior Member
    from nh
    Messages: 529

    clean the balancer recess and get your file out
    i ran mine off the power steering with a double pulley
  3. Megunticook

    Megunticook Senior Member
    from Maine
    Messages: 190

    Thanks. I cleaned the balancer recess with Emory cloth and also the male part of the drive sheave. Still didn't quite fit. Tried a little grease, no dice.

    After a few unsuccessful rounds of Emorying the sheave and trying the fit, I finally pulled out the belt sander and took a good .015" of steel off.

    Went in fine after that. I was actually surprised how easily it went it, I may have taken a little more off than I needed...it was kind of clumsy method.

    But I guess the 3 bolts around the outer bolt circle plus the center bolt being torqued down to 100 ft./lbs. she shouldn't be wobbly or move any.

    A little scary to start removing material off a $180 part (no, that's not a misprint, that's what Fisher charges for #7748).