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 ?

 

[mikester]

Have to agree with DRIVEN above, the pulley is attached to the center hub of the damper not the inertia ring. There is a chance the damper was not fully seated or is working its way out. Were you get a balancer bolt to tighten up in the end of the crank or were the threads pulled and not usable?

You need to read through the 50 pages of the first thread regarding the balancer. Its all explained in there somewhere.

 

[scoti]

This is an area those 'before you remove the existing balancer' measurements sure would come in handy.

 

[Tynan918]

Have to agree with DRIVEN above, the pulley is attached to the center hub of the damper not the inertia ring. There is a chance the damper was not fully seated or is working its way out. Were you get a balancer bolt to tighten up in the end of the crank or were the threads pulled and not usable?

Threads were pulled and not usable...

I been driving around without a bolt in it since July 2021 without this belt issue...

Yes balancer was put on all the way...any more inward on the balancer and the belt would be more than 1 jumped rib...

I know that both trucks and f-body used serpentine belt setups, f-body used the 6.75" balancers, and trucks used the 8" balancers...

That being said, were the serpentine belt brackets the same size ?

Where the crankshaft pulleys the same size ?

 

[WanaBa442]

Threads were pulled and not usable...

I been driving around without a bolt in it since July 2021 without this belt issue...

Yes balancer was put on all the way...any more inward on the balancer and the belt would be more than 1 jumped rib...

Disagree here.
If the balancer was "out" more (as in toward the front of the car) then you'd have the problem as you describe.
The balancer needs to be set further "in" towards the motor to allow the pulley to engage ALL the ribs in the belt.
But, have not seen if all the other pulley drives are on the same plane yet.
Run a straight edge across them all first, you cant get to the end if you don't know where the beginning is.,,,

 

[Tynan918]

The balancer needs to be set further "in" towards the motor to allow the pulley to engage ALL the ribs in the belt.

I used the harmonic balancer install tool to install this balancer and turned it until I couldn't turn it anymore, with someone else holding it from the opposite side...there's no way the balancer isn't on all the way...

 

[Tynan918]

Run a straight edge across them all first

Can you elaborate more please ?

 

[Tynan918]

A 1/8" crankshaft pulley spacer wouldn't fix this problem ?

 

[bruisedbanana79]

Can you elaborate more please ?

Tech Tips

www.cartechbooks.com

 

[ostrich]

That spacer will make it worse, the pulley has to go more towards the motor not the rad. Look at you belt pic the pulley has to go in not out. Means the balancer is not on far enough. Just did mine last week, takes a bit to get it all the way on/seated.

 

[mikester]

If you didnt have a spacer before you shouldnt need one now.