Off track serpentine belt

[Tynan918]

This is the second time my belt has jumped a rib on the crankshaft pulley...

First time I noticed, it was the last belt I had on it, the belt stripped from the same side...

I just replaced the 8" balancer with a 6.75" balancer, and a friend told me maybe because of the different height size balancers, would mean different depth sizes but after measuring the depth on both balancers, they are the same...

...so balancer is crossed out from the list of possible causes.

He said the another possibility he can think of is the crankshaft pulley being wrong depth size, causing the belt to jump a rib...are there different SBC crankshaft pulley sizes between cars and trucks ?

What do you guys think ?

 

[383_GrandPrix]

Find a ruler or flat piece of metal to check if all the pulleys are aligned as depicted in the attached photos.

 

[scoti]

Sometimes a pulley can be spaced DEPENDING ON WHERE THE MISALIGNMENT IS. You first need to determine if the other remaining pulleys are in alignment.

If the other accessories are all in alignment, it suggests something is different w/the crank pulley. Possibilities could be:

* The balancer isn't seated far enough for the crank pulley to align w/the others?
* The new balancer where the pulley seats is shaped different vs the previous unit?

There are different crank pulleys but I recall the differences were between the V6/sbc V8 vs. a BBC V8.

 

[WanaBa442]

Can you elaborate more please ?

Check Engine Belt & Pulley Alignment - MARINE DIESEL BASICS

Check Engine Belt and Pulley Alignment Importance of Correct Alignment and Tension If pulleys and a belt are out of alignment, the is out of alignment Getting Alignment & Tension Right Correct tension and near perfect alignment of the pulleys (sheaves) are the two essentials for long belt life...

www.marinedieselbasics.com

Get a long ruler, or other stiff straight edge and run it on the face of the all pulleys to see where the alignment is off.
You have parallel misalignment.

 

[Tynan918]

Get a long ruler, or other stiff straight edge and run it on the face of the all pulleys to see where the alignment is off.

Find a ruler or flat piece of metal to check if all the pulleys are aligned as depicted in the attached photos.

You first need to determine if the other remaining pulleys are in alignment.

If the other accessories are all in alignment, it suggests something is different w/the crank pulley.

Ok I'll do the straight edge test first thing in the morning.

 

[scoti]

Ok I'll do the straight edge test first thing in the morning.

If it's anything like my big-block set-up was, the straight-edge approach (like using a ruler) was not very applicable. I wound up using some string.

The same rules apply though. The string should make contact on both 'sides' of a pulley so when comparing two pulleys, the string/straight-edge should make contact @ 4-spots.

I'll also say this.....
Did you change any other accessories when doing this work? If no,,,,
Did the belt get off track by a couple of grooves @ anytime before? If no....

Verify the pulleys are aligned (straight-edge/string pull test).
Verify there is no physical difference between the balancer surfaces where the pulley sits.

The balancer is the only part changed so it's most likely that's where something changed if this wasn't an issue before.

 

[Tynan918]

Tech Tips

www.cartechbooks.com

I had a frayed belt edge...

From your link:

"Frayed belt edge: Misalignment of an accessory drive pulley.

An accessory drive pulley can be misaligned in either of two ways: “parallel misalignment” (sometimes called “offset misalignment”), or “angular misalignment.”

Parallel misalignment—the pulley is too far or not far enough onto its shaft, so that it is not in line with the other pulleys—is usually the result of replacing one of the engine accessories driven by the belt.

Angular misalignment—the pulley is at an angle to the other pulleys—results from worn bearings in an accessory. Belt tension on the pulley pulls the shaft off center, which puts that pulley out of alignment with the other pulleys.

Pulley alignment can be checked with a straightedge.

Place the straightedge across two pulley faces.

The straightedge should lie flat across them.

If it doesn’t, one of the pulleys is misaligned.

To figure out which one, check each against other pulleys until you isolate the one that is out of line.

 

[Tynan918]

This is how my crankshaft pulley is lined up with my power steering pulley... (Circled)

The crankshaft pulley sticks out a bit further than the power steering up pulley...with my long screwdriver laying across the face of both pulleys, the only pulley the screwdriver lays flat on, is the crankshaft pulley...

I'll run it along other pulleys as well...

 

[SSMonteMan]

Seems like, to me, everything is pointing to the balancer not being seated fully. Considering the threads on your crank are pulled out, sounds like that's the most logical conclusion.

 

[Tynan918]

Seems like, to me, everything is pointing to the balancer not being seated fully. Considering the threads on your crank are pulled out, sounds like that's the most logical conclusion.

I would assume the same, only the balancer tool didn't free spin as I kept tightening it down...eventually it stopped turning...I even had another guy holding down the other wrench as I pushed on the tightening wrench...it stopped, no free spin... It bottomed out...

Balancer is installed in there all the way, guranteed...

 

[Tynan918]

Could the idler pulley be installed incorrectly ?

Idler pulley looks pushed back further than the rest of it...