<VV> Shop Manual, Corvair Basics Manual, VV

[Jim Simpson]

I do have a strand tension gauge (from the late John Moody) and trust me,
the shop manual specifications are WAY too tight!  If you do actually use a
strand tension gauge and tighten a new belt to 75 lb tension, make sure you
have a spare -- you'll be replacing the fan belt soon.

The 50+ years of accumulated wisdom and experience of Corvair owners (as
opposed to the original engineers) has shown that a somewhat loose belt
works best.  As pointed out in the Corvair Basics manual, just tight enough
so you can just barely turn the alternator/generator with your fingers is
about right.  I measured that as somewhere around 15 - 25 lbs tension
depending upon how well calibrated your finger might be.

I did a little research to see how Chevrolet came up with the recommended
tension and as best as I can find, they used the formulas published by the
drive belt manufacturers such as Gates.  If you make some assumptions as to
loads and RPM, you come up with numbers like 75 lbs tension in order to
make sure that nothing (fan & alternator) is slipping at high RPM.  I
suspect that this high tension specification is one of the reasons why
Corvairs developed a reputation for short fan belt life.  That and the high
rotational inertia of the early steel fans and generators.

The collective experience is that it's better to allow some slippage.

Jim Simpson
Group Corvair