Belts getting thrown off ?
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Intermediate
Joined: May 2023
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Belts getting thrown off ?
My 1978 c3 is throwing belts stock 350 with 4 speed trans every belt I get is like it’s to short and the belts are all at a slight angle possible harmonic balancer ? It doesn’t appear to wobble at idle but maybe at higher rpm it is ? Not sure if anyone has had this problem thanks
Race Director
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From: Sunshine Coast, Queensland, Australia
2025 C3 of the Year Finalist - Modified
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2022 C3 of the Year Finalist - Modified
Cruise-In VIII Veteran
Belts need to be straight. If your belts are to short buy the next longer size.
probable causes, Wrong Water pump. This one is common. A fair few mechanics out there believe there are 2 Chevy small block waterpumps. A short nose and a long nose. Unfortunately, there are 3. The third one is the Corvette only waterpump. Putting on a short nose will fit on the engine but put your belts on a angle.
Harmonic balancer has slipped its ring? Pulleys are bolted to the solid inner hub of the balancer, not likely your problem.
Incorrectly installed accessory brackets. This is also common.
probable causes, Wrong Water pump. This one is common. A fair few mechanics out there believe there are 2 Chevy small block waterpumps. A short nose and a long nose. Unfortunately, there are 3. The third one is the Corvette only waterpump. Putting on a short nose will fit on the engine but put your belts on a angle.
Harmonic balancer has slipped its ring? Pulleys are bolted to the solid inner hub of the balancer, not likely your problem.
Incorrectly installed accessory brackets. This is also common.
Safety Car
Joined: Sep 2005
Posts: 4,226
Likes: 643
From: Orange County Ca
Yes, something is wrong if the belts fly off.
There are different width belts available. A too wide belt, which I suspect you have, will not sit down into the V to the correct depth. A too thin belt will go too deep into the V and rided on the bottom. It may slip because it doesn't grip on the sides.
The correct belt should have the top surface just a little lower then the outside edge of the pulley, and only grip on the sides
Contrary to what some people think, a LITTLE misalignment of the pulleys is not a major problem. It may look bad, but it could work well. Sometimes very hard to get a perfect alignment.
If the supossedly correct belt is to long or too short, take it back to the parts store and get a longer or shorter one. I buy belts from a local parts store, not on line, just for this reason. Easy to exchange for a better fit.
There are different width belts available. A too wide belt, which I suspect you have, will not sit down into the V to the correct depth. A too thin belt will go too deep into the V and rided on the bottom. It may slip because it doesn't grip on the sides.
The correct belt should have the top surface just a little lower then the outside edge of the pulley, and only grip on the sides
Contrary to what some people think, a LITTLE misalignment of the pulleys is not a major problem. It may look bad, but it could work well. Sometimes very hard to get a perfect alignment.
If the supossedly correct belt is to long or too short, take it back to the parts store and get a longer or shorter one. I buy belts from a local parts store, not on line, just for this reason. Easy to exchange for a better fit.
Is my vette stock?? HAHA
Joined: Oct 2015
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From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
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usually you just need a shim to line up the pulleys......pics do help
Team Owner
Joined: Jan 2006
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From: Crossville TN
Belts need to be correctly matched with the pulleys on which they run. There are different configurations of belt cross-section shape. I suspect someone at the car parts store selected the wrong one for you (if you didn't select it yourself). Use the web to figure out EXACTLY what belt you need. Also research how to put the belt on properly and set proper tension.
