Tearing belt edges

At beginning of season I put on new belt on a new to me engine using BDS water pump mounted idler pulley and bracket I have used in past. Which is a KB Chevy 526 conv heads. Littlefield intake with set back littlefield 1471 HHR pulleys are 8mm 25-30% OD. It has an ATI dampener instead of crank hub. Crank trigger wheel incorporated into dampener. (Would rather have hub but that's what it came with). Use 1600 mm carbon GT RCD belts. I set tension by measuring flex in middle of longest side. I set to 1" cold I think this is relatively loose but I don't have crank support. After run or warm up tightens to 3/4". This setting has worked well on similar combo for many years.

First 4 races no problems but at 5th race belt broke. After inspection it starting shredding about a 1" width longitudinally then belt broke horizontally. Don't know which side of belt longitudinal cut started. Assumed belt got loose (idler moved?) and belt got up on top of dampener lip, which is around 1" larger than pulley OD (so about 1/2" on each side), then finally just ripped belt. So put last years belt on with 3/4" tension and torqued idler pulley to 120# and ran 3 more races with no issues. Got new belt and set tension to 3/4" cold. On 2nd pass tore 1" strip off side facing motor on burnout but belt survived the run. Put last years belt back on and set tension to 1/2". On 3rd pass tore 1" strip from outside edge this time.

So what could be causing this? It's happening on both sides of belt so idea that it's getting loose on top of dampener is invalid. I have tried tighter tensions. Will post pic tonight.

Thanks

 

There will be many more technical comments but I will tell ya my blower belt story....1st car came with 13.9 MM and we got the belt super tight when cold - 1st hit it broke at 330 ft. cone when it got hot....so I was very reluctant to ever run a belt that tight....ran em looser after that.....our next belt system was 8MM GT with the good belts (more overdrive choices with 8MM)....broke 3 belts in 1 year (26 runs)....but they were run too loose and I figured the belt was jumping over the tooth on the slack side therefor making it REAL TIGHT again as it was not engaged in the teeth properly....this was also operator error on my part as I was scared to over tighten (see beginning of the post on 13.9 system)....you gotta get the 8MM belts really tight so that they stay engaged with the pulley....we now run 14MM and give em a little slack like you are doing....maybe only 1/2" to 1" total deflection cold....I hope this helps but there is probably a more scientific reason you are breaking belts...

 

Pictures



This is not a 2" belt on a three inch idler. It has 1" shaved off on last run.





Above you can see how the belt got up on the idler. But the belt that shredded before this shredded the opposite side.??









Belt on left is first break after 5th race. Belt on right is 2nd occurrence. Belt on car is third occurrence.

Anybody got any ideas?

 

first of all remove the washers behind the idler bracke and make a longer idler-pulley spacer, also an idler support like the RCD idler assembly will prevent for bending the idler-pulley.

 

x 2 ditto that

 

Belt

Hi Casey,

Is this a new/different manifold? I have seen manifolds that were not flat with the crank raise hell on belts as well.

Best wishes,
Trevor Sherwood

 

Bbc

I never ran with a damper but I had that idler setup before and when you cracked the throttle you could see the idler whip back and forth.eventually I built the plate out of 7075 t6 and made it taller with 2 extra spacers tying into the threaded water fittings on the front of the intake.
When I switched to a screw I ran the plate completely flat against the engine block but had to run a big spacer behind the idler pulley. This setup would flex for sure so I built an outboard support like the hemis run.
I had good luck with all different belts on my Chevys except I never ran 8mm.

 

Belt

I've never had to do it yet but you might consider putting a go pro camera on it.belts do crazy stuff under load

 

Looks like your at the outer edge of adjustment and the plate is flexing. Like the others said an outboard support should cure the problem. You could put more teeth on the pulleys. Keep the same od that will bring the adjustment in, or get a large dia idler if that is the small one. Shorter belt ??

 

Checking in

I don't think the intake is out of true as I'm thinking that if it were it would shave the edge of the belt like it did and continue to push the belt over on that edge?? It didn't do that so that's why I think that's not the problem. This bracket is not the BDS bracket. I got confused when explaining in original post. This was made by the guy I bought motor from and he only put 6 passes on it. Don't know the grade of aluminum. Also the idler dosent have a crown like my BDS one does. On my other car I have the same pulley ratios same belt with BDS bracket and idler and have never had this problem. So the tips about the bracket flexing are making since especially as I shredded 2 at same race when went from 25 to 30 OD so idler farther out. Nitro madness is sending me a front support. Considering swapping brackets but that's an $$ way to test with $200 belts. Gonna try to find a used gopro I guess as need to look at this, my other windshield moisture problem and my dad is also saying dragster is shaking the tires every pass but I don't feel it and it's consistant so I think it's just getting up on the tire or my butts just numb!

Thanks ITA. keep me coming.

 

Belts

Your probably right on the intake continuing to spit the belt off.

I just looked at the photo and these guys are right, that idler setup is nuts, While the outboard is a great idea and recommended we did run a single on the top dragster I worked on and never hurt a belt running 6.20's but we also ran the 11mm 3.5" wide stuff, we also ran a single bracket on a buddies pro mod that ran 4.0's with no problems and that was 8mm 3" wide. One of the first things I did on that TD car was to fix the idler system because he was doing the same thing, washers and such. A couple of properly machined spacers out of the right materials will work wonders. The crowned pulleys are nice but I have seen both work just fine. If you can a dual support system is great but doesn't seem to be entirely necessary.

My money (What little I have) is on the idler setup as well.

Best wishes Casey,
Trevor Sherwood