This is a follow-up to an earlier thread about alternator rpm's.  For the record, my engine is a J-spec 20B.  The crank pulley is 5.5" dia., multi-rib design.  I'm running two 55 amp Geo ND altrnators.  These alternators have a shaft size of .594" and came with 2" pulleys.  I had calculated that they would be turning approx. 21k rpms on takeoff and climb, if they lasted that long.  So, I set out to find larger ones.  Bulent suggested the Honda Prelude alternator pulley as a suitable replacement.  It has a diameter of about 2-3/4".  I found one on ebay, bid and got it.  It came with two stock belts and a stock power steering pulley... all for $5.50.  Not bad, if I could use it.

When the items arrived, I discovered that the Prelude alternator pulley had a larger hole size and wouldn't work without a bushing.  However, the power steering pulley had the right size hole, and was about 3-7/8" diameter.  This would result in about 10K alternator rpm on takeoff.  Only one little problem, it had splines about half way down the hole to match those on the power steering pump.  The rest of the hole was smooth and the right size. So, 15 minutes of lathe work (thanks Bob) and the bores mated perfectly.  Problem solved.  Install a longer belt and its done.  Now to repeat the process for the other alternator.

A side note... the Prelude alternator pulley is the correct size for the Mazda alternator.  So, I gave it to Bob.

Mark S.