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Finally got my car running , but keeps throwing belts off.
Ive attached a picture of the setup we run, the two idler belts are just flat tops.
Straight edge on balancer to alternator , and balancer to tensioner is good.
tensioner to alternator is maybe 1mm out.
belt jumps forward on the alternator pulley about 5mm idle , and if I give it a rev flys off.
originally the guy who built it had 5mm spacers behind the alternator which stopped it flying off but it used to scream on occasion and lose charge, but was still the best setup so far.
im gonna buy a manual tensioner , as I cant think what else is could be, I did swap this tensioner with another though. same issue
There has to be a misalignment somewhere. Best is to sight along the belt where it hits the pulleys. Usually it will be obvious where the misalignment is.
you might want to check out ictbillet, they have a lot of mounting options. the s10 LS swap setup might be what you want to emulate.
you might also want to look at how much tension is on the belt, perhaps get a smaller size belt. how the idlers are set up by the alternator bother me, not sure how the belt riding on the flat surface of an idler will affect the ribs, if that right idler is flat. it's hard to tell from the pic. it could also be that the alternator isn't sitting square, even though the pulley is lined up. that bracket might be tweaked somehow.
The right idler is flat. I didn't want to add a ribbed one yet and complicate things further. I've got a new tensioner now I'll try that tomorrow, if still no luck yeah I'll be looking into those ict stuff.
If only alternator , crank, and tensioner have the ribs how far out from each other would they need to be to cause problems like this.
would 0.5mm / .02"
too much
I think I would start by getting rid of the pulley between the water pump and alternator. Simplify the setup and give it more wrap around the alternator at the same time. Then go from there. Look for any pulleys that lean at all. They have to be perfectly straight or they will push the belt off.
I also take a long extension and with the motor running I use the extension (since it's nice and smooth on the sides) to apply light pressure on the belt forward and backwards between all the pulleys and see what seems to help the belt ride properly and or stop squealing. Then I can narrow down the problem area and look at that area closer.
Can't take that pulley off because the belt will hit the belt underneath, hard to see from the photo.
problem with lining it all up is.
crank balanced is 14mm to centre rib, tensioner is 13mm, and alternator has the long snout so can't put a straight edge against. But I measure that all carefully but it's why I ask if there is any error allowed.
trying my new tensioner today if not I'll try few other things.
No there isn't any tolerance really. It only takes a tiny amount of misalignment to cause problems. Very small amount.
Picture every rib on the belt ans being one single rib that cannot go left or right, it can only bend around the pulleys. That rib has to take a completely straight path all the way around, it cannot flex and contour by bending on the belt's flat plane to try to meet the misalignment, so it will try to find its own straight path which makes it enter the next pulley out of the grooves and walk itself right off.
They have to all be perfectly inline.
The flat sided pulleys don't care, the belt will ride where it rides, but if they aren't perfectly 90 degrees to the face of the engine, in other words if they lean, they will push the belt the direction they lean but the belt may still stay on (seen that a lot) since the ribs will follow the grooves in the pulley and will force the belt to ride where it should on the smooth pulleys, if the smooth pulley is real far off it will also push the belt right off. But if a grooved pulley is out of alignment it's gonna toss the belt off of any of the low walled pulleys. A pulley with high walls will keep the belt on but they don't really make pulleys like that anymore and they walk off with the slightest misalignment
Last edited by 00pooterSS; Dec 6, 2019 at 03:12 PM.
Ive got no idea , everything seems lined up good. put the alternator forward 4mm which is completely out but belt stays in position and doesn't squeak so far. I could try an ICT kit , might be the next idea but I would hate for it not to work as they are expensive.
I'm amazed that a belt stays on there at all. You're running only 2 grooved pulleys out of 6. The belt has almost nothing keeping it in line except for some tension and that's being applied to the wrong side of the belt. Probably better off just running multiple V belts since they take less space and can be run in straight shots without tensioners.
I'm amazed that a belt stays on there at all. You're running only 2 grooved pulleys out of 6. The belt has almost nothing keeping it in line except for some tension and that's being applied to the wrong side of the belt. Probably better off just running multiple V belts since they take less space and can be run in straight shots without tensioners.
3. Alt, balancer, and tensioner, and there's one at each corner so should be okay.
Originally Posted by lscamaro234
Gave up and bought an ict kit now. Will put on this week hope it works. If not will be really confused. Will Let you know.
Hope that fixes it or at least shows you where the issue is somehow during the install of it. The only thing that I know that causes belt issues is misalignment, poor tension, or leaning pulleys. Even a really **** belt will usually do fine if everything else is fine. But if you can turn it by hand and it starts to come off, something is out of line.
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Accessory Belt problems 
something must have been out. 