My understanding is that the deep-groove pulleys were used on engines that would see regular high r.p.m. use. The grooves were deeper to prevent the belts from jumping off the pulley. From an engineering point of view I don't think the diameter of the pulleys (over-drive or under-drive) was important to a mass production car manufacturer, and they tended to stay the same diameter as production pulleys.
The engineers didn't worry about over-speeding the alternator or other driven accessories EXCEPT for the a/c compressor. They kept a/c off the option list for the radical engines, and for cars like the '67 Chevelle SS396 with air conditioning they only came with 3.07 axle ratios regardless of transmission or engine horsepower, in order to prevent compressor damage from over-speed.
It was a big thing back in the 80s/90s to install underdrive pulleys for Mustang 5.0 in order to reduce the parasitic losses. You just have to watch out for an undercharged battery if you don't keep the revs up.
SGS Welding said
January 26th
I think in my particular case
my car already had a slightly under driven factory set up
the water pump pulley is 7 1/8 approx
and the crank is 6 3/4
the only place I found I could get an advantage with factory parts
was the corvette (and some other sporty models) alternator pulley
-- Edited by SGS Welding on Friday 26th of January 2024 11:35:35 PM
Does anyone know?
My best guess for more power to the back tires is
to use the pulleys from a 67 Camaro 302?
Anyone here played the pulley game?
Is there a site that gives specs for all the different pulleys
used over the years?
Here is my crank and power steering pulleys
I cant remember if they are 2 singles or a funny looking double
they are 6 3/4 diameter
short water pump style
Anyone with some racing knowledge from back in the day?
The engineers didn't worry about over-speeding the alternator or other driven accessories EXCEPT for the a/c compressor. They kept a/c off the option list for the radical engines, and for cars like the '67 Chevelle SS396 with air conditioning they only came with 3.07 axle ratios regardless of transmission or engine horsepower, in order to prevent compressor damage from over-speed.
It was a big thing back in the 80s/90s to install underdrive pulleys for Mustang 5.0 in order to reduce the parasitic losses. You just have to watch out for an undercharged battery if you don't keep the revs up.
I think in my particular case
my car already had a slightly under driven factory set up
the water pump pulley is 7 1/8 approx
and the crank is 6 3/4
the only place I found I could get an advantage with factory parts
was the corvette (and some other sporty models) alternator pulley
-- Edited by SGS Welding on Friday 26th of January 2024 11:35:35 PM
How does the speed of the water pump change?
same factory crank pulley
same factory water pump pulley
slightly bigger alternator pulley
the only thing that changes is the alternator now runs a little slower
a tiny bit of power now goes to the rear tires instead of turning the
alternator as fast as the old pulley I removed
or am I missing something?