Vortech/Paxton_Belt Jumping

[gjpundsack]

My 2017 GT 5.0 is seeing the S/C belt jump one rib. Here are the relevant specs: Vortech V-7 JT head; 8-rib kit; 3.3 pulley; ATI 15% crank pulley; Gates green belt #K081000HD (100.58" outside circumference; tensioner adjustment set at the last hole to the right on the driver's side of the car (Vortech calls this the #5 hole). The belt tensioner assembly is the stock one and it only has 6,500 miles on it.

Installed new belt (replacing the original belt which was a Gates K081000 (EOM style black belt) and when warming up at idle, heard a slight noise, shut her down and found the belt had jumped one rib on the ribbed idler pulley between the S/S steel plates that mount the S/C to the engine. No belt damage visible. Pulley routed in place correctly on all pullies. Belt is aligned properly (in the grooves) in the ribbed pullies on the S/C, the water pump, the alternator and the crank. Same thing with a visual on the smooth pullies. All pullies in the assembly with snap rings holding the bearings in have the snap rings facing the radiator.

As a part of the new belt installation, I had first set the tensioner adjustment at the second hole from the right on driver's side of the car (#4). But, I couldn't get the pulley on the tensioner pulley. It seemed as if the belt was too short. Took the mounting assembly apart and moved it to the #5 hole. It took a little pressure to get the belt onto the tensioner, but not too much. Turned the engine over by hand with a socket on the crank bolt and visually checked everything before fire-up. Belt was properly aligned. All pullies turned freely with out the belt. All pullies looked to be the same distance from their rear side to the S/C mount plate that bolts to the block. replaced all grade 5 fasteners with grade 8 bolts and washers.

I'm at a loss to understand why this is happening. Can anybody help?

I wonder if it has anything to do with the tensioner assembly.

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[beefcake]

99% it is in the tensioner assembly,

i would pull it back apart and mic all the spacers

 

[gjpundsack]

99% it is in the tensioner assembly,

i would pull it back apart and mic all the spacers

 

[gjpundsack]

I think you're right. I now suspect its because I mounted the ribbed pulley in the #5 hole and not the #4 hole hole causing the belt to "whip". The first belt installed--when everything was okay--was in the #4 hole. The other two belts I bought are the same size as the first. So, they should go on the same setting. Because it was so hard to do, I went to the #5 hole. Gonna try it all again this week. Will post results.

 

[Justa3v]

I have the same issues, whatever became of this?

 

[andrewtac]

I am fighting this with my 10 rib setup, made a post the other day. I never had issues with the 8 or 6 rib, and I am using the same brakets. I think the smooth tensioner prior to the ribbed tensioner might not be square, as I can see the belt bounce slightly on this pulley, which pushed the belt out and causes it to jump off the grooved pulley. I now have a phaser issue so not able to troubleshoot the belt issue until I get this sorted.

 

[Justa3v]

Mine does the exact same thing, it’ll jump back and forth from the position it should be on the rib, to 1 rib forward( wrong location).
I think it’s the ribbed pulley, (exasperated by the griptec pulley, and 10 rib alt pulley.

Ian going to shim the bracket pulley over with a washer and see if that affects the blower pulley. If it doesn’t I’ll keep this in place. If it messes up the blower pulley, I will remove some material from the smooth pulley shim, directly in front of the ribbed pulley.

 

[andrewtac]

I used a couple washers to space the ribbed pulley out and the belt would stay on. I made a few pulls to 8k like this and it worked. However you could still see the belt bouncing on the smooth pulley prior to the grooved, it tries to ride off the front of this pulley, but being smooth it bounces back. I think spacing the grooves pulley allows it to work but doesn't necessarily fix the issue. With the grooved pulley spaced out I did not have any issues with the blower pulley and the two smooth ones adjacent to it. I think the griptech realligns the spaced forward belt. I really wanted to try to address the issue, hopefully at some point I'll get back to it.

 

[Justa3v]

Thanks for responding to this, this is all good information

 

[Brevin]

Thanks for responding to this, this is all good information

I have seen this a few times and it is almost always an alignment/offset issue. I have seen griptec pulleys with incorrect offset cause this. First thing I would check is an OEM Vortech pulley offset vs the offset of your griptec. Put them both next to eachother on a flat surface and compare the ribs to see if they align. If those are the same I would buy/ rent a laser alignment tool and check alignment of all ribbed pulleys in relation to the crank. For it to jump like that on a 10 rib belt it would need to be off fairly significantly. This is the laser I’ve used and it should help narrow down where the issue is. I believe some auto parts stores rent them.​

https://shop.advanceautoparts.com/p/dayco-belt-diagnostic-kit-93874/10030803-P
​

 

[Justa3v]

I have this exact device, and all ribs line up including the griptec.

I went straight to 8 rib. 6 rib was never used.
I used American racing solutions for the 10 rib pulleys on the alt and water pump.
( due to 10% OD damper)

I am starting to think, the bracket or a pulley is out of square in the bracket.

 

[andrewtac]

I have the laser tool, the griptec, water pump, and alternator were all aligned with the balancer. When I pull the blower off I'll check the idlers. I am not sure the laser will show if a smooth idler is tilted in the vertical or horizontal. I might be able to scribe some lines on it and see if it is out if plane. I think a tilt of a smooth pulley would cause what I am seeing. There is something wrong on mine still, it is between then tensioner, first smooth idler and the ribbed idler. I've tried several tensioner, and moved the grooved idler out, also tried a different smooth pulley. I got a 12 rib smooth idler and a custom spacer built. Thinking the belt was hanging off the 10 rib smooth and that was pushing the belt out. With the 12 rib pulley it actually shifted even further forward, this is what made me think it might be out of plane.

 

[andrewtac]

We replied about the same time, that us what I think my issue is. I bought a small machine square I plan on checking with when I pull the blower off.

 

[Justa3v]

So as an update and hopefully to help others, I added 1 washer to the ribbed idler, in the bracket, I added 1/16th shims to the tensioner pulley.
My belt jumping is fixed, and the belt does not turn or have a hump at the smooth idler before the ribbed idler in the bracket.

thanks for the help and pointing me in the right direction.

 

[andrewtac]

I am tearing the motor apart to put new springs on the heads, another story. Anyways, I ordered an MPF bracket with crank support. I suspected my bracket wasn't true and this was causing the issues. The washes were just a bandaid, and probably would have worked. This is the pulley I thought was causing the issues. Got a quality square on it. The pulley is tilted down, causes a normal force on the belt as it goes over the pulley, pushes the belt forward, which causes it to jump off the ribbed pulley. I also put a straight edge on the back of rhe bracket once I removed it, visible bow. I suspect the 8 rib belt being more narrow, and the 8 rib pulley being more narrow and smaller diameter put less normal force on the belt, and probably why I didn't have problems until I went 10. Hopefully I get the motor back together in a couple months and install the MPF bracket and all my problems will be solved, not going to hold my breath.....race car life.

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