Slipping belt
Thread Starter
Racer
Joined: May 2014
Posts: 396
Likes: 36
From: Victoria BC
Slipping belt
I've been driving my 69 L36 roadster all summer after restoring it last winter. I have worked out all the bugs, except I can't get the alternator belt to stop slipping when I get on it. I know I have the correct alternator pulley the other two pulleys are 3 groove , which may not be correct, as the car was not ordered with power steering or air, but I'm sure the grooves would be the same anyway. Someone told me that you can buy a deeper v belt which would get more traction, but I asked at the auto parts store, and they told me no. Just wondered if anyone had had the same problem?
Race Director
Joined: Apr 2011
Posts: 11,183
Likes: 3,335
From: North of Toronto - Ontario
OK, here's just the normal reminders
Check the tension, put a socket on the alt nut and give a good pull, it should try to turn the motor (it won't with the plugs in) before it slips. Seems like we generally don't tighten them enough, plus the newer belts don't stretch much so they feel tighter than they are.
I've had better luck with the notched belts (internal or external, my preference is the Dayco Topcog) which bend easier and seem to be less likely to want to run off at higher rpm.
If the pulleys are out of alignment, at higher RPM or load the belt will try to walk up one side of the pulley
If the belt is glazed from slipping, it'll keep getting worse
if the pulleys are worn the sides aren't going to contact the sides of the belt very well
belt dressing is only good for an hour or two, mainly for selling cars I believe
M
Check the tension, put a socket on the alt nut and give a good pull, it should try to turn the motor (it won't with the plugs in) before it slips. Seems like we generally don't tighten them enough, plus the newer belts don't stretch much so they feel tighter than they are.
I've had better luck with the notched belts (internal or external, my preference is the Dayco Topcog) which bend easier and seem to be less likely to want to run off at higher rpm.
If the pulleys are out of alignment, at higher RPM or load the belt will try to walk up one side of the pulley
If the belt is glazed from slipping, it'll keep getting worse
if the pulleys are worn the sides aren't going to contact the sides of the belt very well
belt dressing is only good for an hour or two, mainly for selling cars I believe
M
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Sometimes (well, a LOT of times), the auto store clerks can pick the right LENGTH but the wrong TYPE of belt. There are different angle/groove configurations. They must make sure that they have the correct LENGTH, STYLE, and WIDTH belt, if it is to fit properly. You can measure groove WIDTH at the outside edge of the pulleys. It is possible that you have pulleys of different widths for the alternator belt. In that case, you need to install a belt sized to the largest width of the pulleys in that system. If you don't do this, the belt will just slip in the widest width pulley.
Drifting
Joined: Jul 2004
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From: Kissimmee fl
Finalist 2021 C3 of the Year - Modified
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St. Jude Donor '07
Does the waterpump pulley have 2 grooves? My SB needed the belt from the WP to the crank to stop the squeal.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
If your engine came from the factory with only ONE powered accessory, it would have had that crank-to-water pump belt in addition to the single accessory drive belt. If it had TWO driven accessories, then it would only have the belts for those two devices and not the crank/waterpump belt. GM wanted to have TWO belts driving the water pump at all times, so that if one broke, the pump would still function to cool the engine while 'limping' home.
If you only have one accy belt now, you do need to add the crank-to-waterpump belt, as only one is not really adequate to drive the pump and prevent squealing.
If you only have one accy belt now, you do need to add the crank-to-waterpump belt, as only one is not really adequate to drive the pump and prevent squealing.
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Thread Starter
Racer
Joined: May 2014
Posts: 396
Likes: 36
From: Victoria BC
If your engine came from the factory with only ONE powered accessory, it would have had that crank-to-water pump belt in addition to the single accessory drive belt. If it had TWO driven accessories, then it would only have the belts for those two devices and not the crank/waterpump belt. GM wanted to have TWO belts driving the water pump at all times, so that if one broke, the pump would still function to cool the engine while 'limping' home.
If you only have one accy belt now, you do need to add the crank-to-waterpump belt, as only one is not really adequate to drive the pump and prevent squealing.
If you only have one accy belt now, you do need to add the crank-to-waterpump belt, as only one is not really adequate to drive the pump and prevent squealing.
Thread Starter
Racer
Joined: May 2014
Posts: 396
Likes: 36
From: Victoria BC
Awe , never thought of that, I was thinking I would have to take it right off, which as we all know is a b*#€£ to get back on , thanks for the tip!