Floppy belt.

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firstgencamarojunkie
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Floppy belt.

Post by firstgencamarojunkie »

Well, I guess I'm not immune - out for a test drive when I suddenly hear a whining sound like a spooling turbo. Was on freeway and really couldn't stop,wasn't too worried as fan idiot light remained off and temp was normal. Thought perhaps turbo was having an issue, but back in garage saw the belt had flipped. Tried resetting it and flipped two more times. Car came with two "new" (?) Belts - Goodyear gatorback 15565. Seems to fit.. is this belt ok to run? Pulleys and such seem ok. Can I assume a worn belt or......?
66vairguy
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Re: Floppy belt.

Post by 66vairguy »

Wrong belt. Auto stores list the wrong part for Corvair.

Use Gates 3V560.

Once a belt "flips" it's junk. Not sure why, but it's reported a flipped belt will just keep flipping, or come off.
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bbodie52
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Re: Floppy belt.

Post by bbodie52 »

It is unusual for a street-driven late model (1965-1969) Corvair to flip fan belts. The cumulative mass of the rotating fan and generator/alternator is continually at war with the changing rotation speed of the crankshaft pulley. Manual transmission cars in particular place a lot of stress on the belt as the engine revs up to speed and then suddenly drops off at each shift. The "flywheel effect" of the heavier steel fans put a lot of strain on the fan belt as the crankshaft speed changes and the heavy steel fan resists the engine RPM change. The fan belt ends up straining with each engine speed variation, and the lightweight magnesium fan greatly reduces the stresses involved. The lightweight magnesium blower and belt guides seem to work very well — with minimal stress on the belt.

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The belts do fatigue with age and should be replaced every few years as a precautionary measure. It is usually not a good idea to reuse one after it has flipped — even if it looks OK and seems to be intact. Internal damage to the hidden tensile support strands can occur if the belt flips and is forced to ride up over the pulley structure. If a new belt flips it may have stretched with "break-in" mileage and might have needed to be re-adjusted. If you repeatedly have such problems with your Corvair there may be a problem with excessive drag in a faulty fan or idler pulley bearing, or a problem with the alternator bearings. A failing harmonic balancer can also cause belt problems.

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The image above displays the support strands that are embedded around the perimeter of the belt to provide it with tensile strength. A belt that has flipped off from the Corvair pulleys on its own may have suffered damage to these support strands that are internal and hidden from view. However, one or more damaged strands within the belt can severely weaken its overall tensile strength, which means it is likely to flip off again as it stretches if a damaged belt is reused.

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There are two 9/16 inch fasteners securing the idler pulley. The hole and the separate groove (or slot) in the above photograph shows the locations where bolt and nut tension is applied to secure the idler pulley in place. Late-model cars that are fitted with a magnesium blower also have belt guides at the idler pulley and at the main fan pulley. Specified clearance between the belt/pulley and each belt guide is 1/16 of an inch. The idler pulley tension must be adjusted to provide both proper belt tension and proper clearance between the belt and the belt guide.

A good rule of thumb (literally) when adjusting belt tension is that proper tension has been achieved if there is a slight slippage between the belt and the alternator/generator pulley when pressure is applied with your thumb to the alternator/generator cooling fan blade. If there is no slippage the belt is likely too tight.

Tightening a Corvair fan belt w/ordinary tools
1961 Shop Manual, Page 7-4 wrote:Adjust belt (if necessary) to give a 3/8" deflection between blower and idler pulley under a 15 pound load. If a new belt is installed, adjust deflection as described above, then operate the engine at 1500 rpm for at least one minute to "seat" the new belt. Recheck deflection.
If you have a harmonic balancer on your engine, you should check it for signs of slippage between the center crankshaft hub and the outer harmonic dampener. The two steel components are held together in a press-fit by a rubber ring. This rubber component can deteriorate with age, which can permit slippage of the outer steel dampener. A slipping outer dampener makes for an inaccurate timing mark, and the outer ring will eventually completely separate. If the register mark between the inner hub and the outer ring shows signs of slippage, the harmonic balancer should be replaced with a new harmonic balancer.

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Brad Bodie
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Image 1966 Corvair Corsa Convertible
firstgencamarojunkie
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Re: Floppy belt.

Post by firstgencamarojunkie »

Thanks Brad / I probably should have mentioned it's a '65 Corsa Turbo. May have been my own doing as I was trying to see how much boost I could get out of the turbo - and - had to back off quickly a couple of times as I heard detonation. I plan on retarding the timing a little tomorrow to see if that fixes the pinging. I know the pressure retard is working as I tested it on the car with a controlled air source. Eventually I plan to install an EDIS system so I can map the entire RPM range.
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Danny Joe
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Re: Floppy belt.

Post by Danny Joe »

If your belt shows excessive wear, make sure there is no rust in the pulleys. It acts just like sandpaper. I had belts worn down to half the original width. I probably went through 4-5 belts before finally sanding the last pulley smooth, have been using the same belt for close to 20,000 miles now.
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firstgencamarojunkie
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Re: Floppy belt.

Post by firstgencamarojunkie »

Thanks Danny, sounds like good advice. I also see many post saying spray the belt with silicon.
66vairguy
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Re: Floppy belt.

Post by 66vairguy »

As I posted already --- your 15565 belt is too WIDE. A problem well documented by experienced Corvair folks about belts being too wide causing problems. Those with experience state the narrower 3/8" Gates 3V560 is the same width as the original Corvair fan belt. Clark's also sells a "wrapped" fan belt (similar to original) that is the correct size.

The 15565 is 0.44 (7/16") wide. Yes the extra 1/16" makes a difference. The experts note it rides too high in the pulleys.
firstgencamarojunkie
Posts: 126
Joined: Sun Jul 27, 2014 2:08 pm

Re: Floppy belt.

Post by firstgencamarojunkie »

Thanks '66' - already ordered two "Otto" belts from Clark's. Too bad they're on the "other coast" :ty:
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