Okay, I just broke my second idler pulley, the one provided with the 8 rib kit. I figured the first time it happened that it was just an anomaly. Apparently that's not the case. Both pulleys broke in an identical fashion, and both belts shredded in half at the moment of pulley failure.

I've got the Whipple with 13 PSI pulley, 8 rib kit, and Kenne Bell tensioner.

1) What would you do to solve the problem?

2) Should I purchase an aftermarket pulley, something a little stronger?

3) Is this common on forced induction vehicles?

4) Is it normal for the belt to break at the same moment the pulley fails?

 

Here are a few WAGs

a) why a KB idler with the Whipple kit? Any physical difference to the Ford one (diameter, width)?

b) Is it possible you are over tightening the belt (I have not had the belt off this V8 yet, but gaging from other installations, the system usually has a spring loaded idler that self tensions the belt?).

c) is it possible you have an belt alignment problem with the idler? Missing a spacer on the pulley or something that could cause abnormal belt loading on the pulley?

 

I am with Paul, I'd be making some phone calls and checking my clearances, alignment, and torque specs Monday.

 

You should be following this other thread about blower belt failures. Appears its related to the durability of the tensioner and the size (diameter) of the idler pulley.

 

I'm definitely following those threads, and probably contributed to most of them. Oddly no one has posted of a broken idler pulley in those threads. When I posted this thread, I really just wanted some input as to whether idler pulleys should break at all. I've found plenty of aftermarket pulleys, so I'm led to believe stock pulleys break on high horsepower cars.

I've also purchased thump_rrr's custom tensioner. Hopefully I can just replace the entire system with stronger parts and be done with it.

 

The KB tensioner is just a stock tensioner with an additional billet arm welded to it. Nothing special.

I may be overtightening, but until someone takes a look at it for me, I'll never really know.

I have a spacer behind the idler pulley that's breaking. It's a wider 8 rib pulley. For now I'm just going to upgrade the pulley with a billett one. See where it goes from there.

I installed a Meziere pump yesterday to keep me from being stranded. Luckily my pulley failed (both times) near home.

 

Talk more to the guy who mentioned idler pulley diameter. This will have a direct affect the belt tension and that appears to be a critical factor. Coming off WOT and high RPM may be creating some belt / belt tensioner system dynamics. If the dynamics is such that the tensioner unloads during engine deceleration that might be setting up some cyclic load variation (belt whipping) leading to belt or component failure (your idler). The beefed up arm shown on that other post looks like a killer part, but if the system dynamics is not right (belt tension), failed belts may still b problematic and the root cause has not been cured. The spring rate of the tensioner may have something to do with the problem as well.

 

Whipple now recommends using the 90mm idler pulley that is removed from the drivers side(replaced with a Whipple supplied 100mm idler)be used on the tensioner in place of the 76mm stock idler. Hopefully this will work.

 

One word : Thump_RRR racing stuff

Nobody was able to broke it, 100% more than happy customer.

 

Hey Claude,

You will be the first to have our new billet 90mm idler pulley on your tensioner.
We just ran the first batch this morning and I'll be shipping it out tomorrow.

 

The only reason that pulley diameters are critical is to allow the tensioner arm to remain as far away from the stop as possible.
The only reason the Thump_rrr tensioner uses an upper stop is so that the tensioner bolt closest to the arm can be installed without the need to keep tension on the tensioner.
The limiting factor on the Whipple and Kenne Bell setups is the limited selection of belt lengths which is why they have adjustable idlers on both systems.
With the Saleen there is quite a variety of belt lengths available such as 107.5, 108.8, 109.2, 110.0.

If for some reason you end up wih less than 5/16"-3/8" clearance to the stop we recommend that you remove the setscrew.

Our tensioner is setup with 25% more tension than stock but we also proved the functionality of the system with stock spring tension.

The stock tensioner was never designed to run a blower belt but to simply drive accessories which is why it is a cast piece with a plastic bushing and not a billet piece with needle and ball bearings and a 4340 hardened shaft.

 

Great info.

 

Thump, I'll measure the distance in mine today, but I have noticed the stop has hit the tensioner, I can see the marks. Is that a big deal?

 

This is your solution. Period!!