Belt tightness

[1956322]

How tight should the generator belt be..I  think  it's tight enough but I can watch it jumping all over the place.. Trying to figure out if my random noise is belt related.. Can't drive with the belt off it's to random to know when it'll do it but occasionally on take off I hear a popping doesn't last long can't figure this out..56 322

[Guest]

It shouldn't be jumping anyway.  A rule of thumb is put a straight edge from water pump to generator, depress the belt at the half-way point.  1/2 inch deflection would be normal.

[Beemon]

 

The shop manual goes into detail with belt tightness. Belt tightness should be 3/8", 1/2" for AC cars.

 

If your generator pulley is tight, then you might need a new pulley. Likewise, make sure water pump and crank pulley are tight. If using power steering, then the pulley channel closest to the engine is for the generator. Also check to make sure the generator is mounted correctly with both legs on the outside of the bracket and the adjusting arm on the backside of the top leg.

Edited March 6, 2017 by Beemon (see edit history)

[old-tank]

Replacement belts are cheap enough, so replace it.  The replacements will have notches on the pulley side for noise control.  On mine, using a belt without notches produces a popping sound.  When adding A/C to the nailhead in my 51 F-1, I left off an idler pulley and there is some belt whipping that sounds like a rumble.  The original belts had no notches, but were fabric wrapped like lawn equipment belts.  Now you have a spare to carry in the trunk!

[1956322]

Thanks for that..I  have  one inch deflection so that's not right wondering if that's causing my random popping sound in take off... Should the power steering be the same 3/8....I  do  hados manual but left that in storage lol

[Beemon]

There isn't a deflection reading for the power steering. I'm always tried my best to pull it tight in one hand and tighten with the other. Usually results in about the same belt deflection, with no issue.

[1956322]

Ok so I got my pry bar out and got her tightened up I measure 3/8th deflection with at most 1/2 if I really push down..I  think  I'm good there so hopefully no more random popping

[NTX5467]

 One KEY thing about v-belts is to have the correct width of belt for the PULLEY.  On later model cars, about the only place GM spec'd a notched belt was on the late 1970s Cadillac Eldorados with the 100amp alternator with the SMALL pulley on it.  They needed the notched belt so it'd make the "wrap" around that smaller pulley as a non-notched belt wouldn't "make the turn".  Of course, they can be used in other places they didn't normally come, too.

 

In those same general model years, GM would use a 3/8" belt in production and then spec a 7/16 belt "for service replacement".  Using the wider belt in place of the 3/8" belt would mean you also needed a LONGER belt, about 1" by observation, than what was stamped on the 3/8" belt for length.

 

When the two pulleys are far apart, the "whipping" is part of that equation.  Trying to tighten things so that it doesn't happen or is minimized will put additional loads on the front bearings of the particular driven items and shorten the life of those bearings.  Might even lessen wear on the lower half of the front main bearing, too!

 

When any drive belt is new and stiff, do an initial adjustment "to spec".  Then about 1000 miles later, after it's got some time on it, re-adjust to specs and that one should hold for a long time.

 

NTX5467

Edited March 7, 2017 by NTX5467 (see edit history)