gthill13

I recently converted my 4-rib MP 62 to a 6-rib. Had it humming along for maybe 6-months with the crappy stationary pulley that came with kit until the bearing imploded. I converted to a dayco auto tensioner and continue to work through alignment issues. I ended up getting the alignment laser and everything checks out including the front to back tilt. I continue to have the belt moving one rib forward on the nose pulley. I also went with a slightly shorter belt that was a real bitch to get on. This one worked good for two days and did not jump off but separated along the ribs two times in a row. I am now wondering if it could possibly be that idler pulley needs to be moved in a little. I noticed that the belt is at the extreme edge of the idler when on both pulleys and seems to sit a little better when it is off a rib on the nose pulley.

Was going to shorten the standoff bolts to move the idler pulley in about 6mm. Am I flailing or does that sound reasonable?

gthill13

I found a local machine shop to shorten the standoff nuts by 6mm and will see if that makes a difference with the belt tracking. Unfortunately won't have time to work on it for another week. Should have taken some before pictures, but will be sure to post some after photos.

RunninOnEmpty

iTrader: (5)

6mm is equivalent to about a quarter inch, might be easier just to find an equivalent stand-off of the same thread. (McMaster Carr, or Ace Hardware?) Even if it were a little shorter, you could shim it with washers, which might be helpful to fine tune.

just going to throw an idea out here…. What if your charger is back too far? How about pushing it forward a bit? I remember you stating the belt would rub the water pump pulley…. Using flat stock or a laser to align pulley planes only works if the pulley edges are of the same thickness, otherwise the faces are actually off. Also, it is possible that it’s slid back over time.

I’d try loosening the bolts on the two vertical brackets, then giving it a tap forward. Another idea, just do like BOFI does with their kits and stick an 8 rib on there. It’ll find it’s natural spot and you’re done. Or the cheapest option I ran with for a good while, run 5 ribs (happened when my outer rib tore off just like yours did).

you shouldn’t need a really short belt. The autotensioner should be doing the work. It just can’t help if things are misaligned.

Godless Commie

iTrader: (2)

I had an MP62 setup for 10 years. Ran anywhere between 8 to 18 PSI using a number of pulley combinations.
There were times when the belt was just fine for months, and others where I was replacing belts every couple days.
Did everything I could to align things, including micro machining the autotensioner plate standoffs to make sure the damn belt stayed on.

You know what cured the belt problem?
Removing the damn power steering belt! Yes. The PS belt.
I promptly converted my PS to electric (no belts, yay) and ran it that way until I got sick of the whole SC thing, removed it and proceeded to install a progressive twin turbo setup.

I believe the crank (and the crank pulley) goes out of alignment when the revs climb quickly under high load, and removing the PS belt reduces some of that load from the crank.

Ted75zcar

iTrader: (2)

I too have been running SC for years, and I build my own DIY compound craziness. I have zero belt issues.

The #1 issue I have seen people have is alignment, and everybody always insists that their belts are aligned. They also usually align using the pulley face instead of the pulley groove, which is the wrong way. Alignment should always be referenced from the groove. I use a precision ground edge to get it right.

I do not run any other accessories other than an alternator, I did run AC with my original JRSC.

gthill13

I checked the thickness of the pulley walls and did see that the crank pulley was slightly thinner, but either way I absolutely agree with what you are saying. I know that I was dead on with the laser and back checked with a straight edge across the pulleys factoring in the thickness issue. Tried to check the blower angle best I could but still no luck. Going to try to build a stationary tensioner instead.

gthill13

I came across your 2014 post which detailed all the maneuvering you went through with pulley issues and decided to try a stationary approach. I will report back with the progress over next month or so as I get time to tinker. The general approach is a 1/4 inch steel plate mounted to the standoffs with a TDR tensioner mounted on top of that. It may be hair brained but it makes sense in my head based on the fact that the stationary tensioner that came with the upgrade kit worked for a bit.

Icedawg

Indeed, another belt saga
sorry, just came to mind, inspired by the thread title

RunninOnEmpty

iTrader: (5)

I dunno, I think you’re overthinking it. Yes, a lot of info to take in. But there are plenty of other 6-rib setups - FFs coldsides included - that are using a simple crank, sc, autotensioner setup. None use extra pullies as guides, across relatively long distances.

You know your belt is uncomfortably close to you water pump pulley (I think it was that one), you feel the autotensioner isn’t quite aligned to give even pressure to the belt (which could stretch the belt weirdly). You feel the belt is naturally tracking and preferring one rib off. I’d go with your gut based on what you’re seeing once the engine has ran, rather than relying on laser precision in a static environment. By no means scientific, but you just want the car running. Your findings really won’t apply to anyone else. So a little unexplained voodoo is okay if it solves your problem,

I’d still try humoring me, and throw on a thinner 4-rib or your torn-off belt, stick it dead center, and let it track for a few days. Adjust the SC around where the belt wants to naturally travel. Adjustment is literally the two vertical mounts, or taking some washers and shimming the SC pullie forward after filing out a key way. That work will take you an hour and less than $1 rather than tooling stuff that others haven’t usually needed.