Serpentine belt rpm limit?
02-07-2019, 09:05 PM
#1
ModSquad
Thread Starter
iTrader: (6)
Serpentine belt rpm limit? Got the car out today. It was in the 70’s and absolutely beautiful. Picked the boy up from baseball practice, and we all went to dinner in it. Had a great time until on the way home, I hit my rev limiter, which is set at 7800ish I think, and my serpentine belt shredded. It didn’t snap, it kinda de-laminated, for lack of a better way to describe it. 3 of the 6 grooves on the belt just flew to pieces, and in the process, took out my power steering line. I’m running Holley Corvette style accessories, and my a/c was off. Everything is new of course. All my pulleys are fine. It was the belt that came with the Holley set up. I’ve never seen this before. Anybody out there ever seen a belt do this?
02-17-2019, 07:58 PM
#2
TECH Senior Member
iTrader: (7)
I was shredding belts when I had my LS6 powered RX7. I swapped over to the non-spring loaded tensioner from Katech and never had a single problem since. I've used them on 2 other builds since then without any problems. Katech developed these tensioners a long time ago for the C5R racing program.
My only complaint is that the anodizing is not color fast and will fade when exposed to sunlight. This is not a problem for most, but my Cougar has a hole in the hood and the tensioner has faded as a result. Still works perfectly. I wish they would use Type III hard anodizing.
Andrew
My only complaint is that the anodizing is not color fast and will fade when exposed to sunlight. This is not a problem for most, but my Cougar has a hole in the hood and the tensioner has faded as a result. Still works perfectly. I wish they would use Type III hard anodizing.
Andrew
02-17-2019, 08:08 PM
#3
TECH Addict
I've seen a small shock used on a belt tensioner to prevent the belt from flapping due to harmonics.
Also matters how long the gap is between pulleys, longer distance is more likely to flutter.
+1 on the mechanical tensioner I get about 50K out of a belt on my jeep with a solid system.
Also matters how long the gap is between pulleys, longer distance is more likely to flutter.
+1 on the mechanical tensioner I get about 50K out of a belt on my jeep with a solid system.
02-19-2019, 06:05 PM
#4
ModSquad
Thread Starter
iTrader: (6)
Guys, I super appreciate the info! I’ll look into that tensioner.
02-20-2019, 04:31 PM
#5
I haven't seen that exact situation but I used to toss belts and have them fly off in situations where it revved real fast then slapped a gear.
So on my slow poke car it always happened on the 1-2 shift.
Increasing tension eliminated problems. I did it through a truck alternator and a buick high wall tensioner pulley. The truck alt sits a little further out and the buick high wall is a little bigger in diameter, both lead to pulling on the tensioner more which puts more tension on the belt.
All that being said, I vote for a new gates belt and higher tension on it.
some talk about throwing belts and shredding
https://ls1tech.com/forums/new-ls1-o...oming-off.html
Pics of the high wall pulley in post #7
https://ls1tech.com/forums/generatio...ing-belts.html
buick pulley info
https://ls1tech.com/forums/generatio...swap-pics.html
So on my slow poke car it always happened on the 1-2 shift.
Increasing tension eliminated problems. I did it through a truck alternator and a buick high wall tensioner pulley. The truck alt sits a little further out and the buick high wall is a little bigger in diameter, both lead to pulling on the tensioner more which puts more tension on the belt.
All that being said, I vote for a new gates belt and higher tension on it.
some talk about throwing belts and shredding
https://ls1tech.com/forums/new-ls1-o...oming-off.html
Pics of the high wall pulley in post #7
https://ls1tech.com/forums/generatio...ing-belts.html
buick pulley info
https://ls1tech.com/forums/generatio...swap-pics.html
Last edited by 00pooterSS; 02-20-2019 at 04:37 PM.
02-20-2019, 05:35 PM
#6
For fast shifting transmissions, the best relief for the accessory drive is an alternator one-way clutch pulley, or de-coupler pulley. Unfortunately GM does not use them much, Ford and FCA do. The alternator has the highest amount of inertia / momentum spinning mass, combined with the smallest pulley, so it has the hardest time slowing down quickly and without slipping and causing momentary slack in the system.
They were first brought to mass market when auto transmissions went to electronic control due to their fast shifting ability. There would be a momentary belt chirp during full throttle gear changes.
They were first brought to mass market when auto transmissions went to electronic control due to their fast shifting ability. There would be a momentary belt chirp during full throttle gear changes.
Last edited by FormulaBoat; 02-20-2019 at 05:41 PM.
02-20-2019, 06:30 PM
#7
ModSquad
Thread Starter
iTrader: (6)
Pooter, I appreciate the links sir. It looks as though I need the Katech tensioner. My belt isn’t throwing off...it simply slung half of itself apart. From reading up on it, it appears as though it’s because of slack and slipping caused by the tensioner.
FormulaBoat, your info makes sense. I never thought about pulley deceleration in the alternator, but you are correct. There was substantial belt dust on the alternator itself, from the belt slippage there due to exactly what your saying.
I really appreciate the help guys!
FormulaBoat, your info makes sense. I never thought about pulley deceleration in the alternator, but you are correct. There was substantial belt dust on the alternator itself, from the belt slippage there due to exactly what your saying.
I really appreciate the help guys!
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02-20-2019, 06:50 PM
#8
TECH Addict
De-lam can be caused when the pulleys "stop" faster than the belts your putting the laminations of the belt in shear and they dont have much strength that way. Thats why the decouple works, when the belt gets stretched then relaxes it causes harmonics, Use a timing light to stop action your belt while revving the engine up and down, I've seen 4" of throw on a 24" gap.
02-20-2019, 06:51 PM
#9
TECH Addict
Oh and on serp belts the best investment you can make is a good tension gage, made a huge difference on belt life on my jeep I went for 12 to 15 K miles to about 40K..
02-20-2019, 07:16 PM
#10
Pooter, I appreciate the links sir. It looks as though I need the Katech tensioner. My belt isn’t throwing off...it simply slung half of itself apart. From reading up on it, it appears as though it’s because of slack and slipping caused by the tensioner.
FormulaBoat, your info makes sense. I never thought about pulley deceleration in the alternator, but you are correct. There was substantial belt dust on the alternator itself, from the belt slippage there due to exactly what your saying.
I really appreciate the help guys!
FormulaBoat, your info makes sense. I never thought about pulley deceleration in the alternator, but you are correct. There was substantial belt dust on the alternator itself, from the belt slippage there due to exactly what your saying.
I really appreciate the help guys!
Yours self destructed for the same reason mine was flying off. Same fix. Should have stated that.
I like the idea of the katech tensioner, but anytime I can have zero issues and keep a spring loaded tensioner I'm going to go that route. Easier on all the bearings and belt.
You could do the katech and the buick high wall and have a really nice setup too. However the high wall may not be necessary if it isn't slinging it off. I liked the looks of it though and I think it was $8 for the pulley.. essentially I saw it as cheap added insurance and since it had a larger OD it kept more tension on the belt and everything was gravy after that.
Last edited by 00pooterSS; 02-20-2019 at 08:31 PM.
02-20-2019, 07:17 PM
#11
Do you happen to have a 90's 4.0 inline 6 in that thing? Early in my career as a tech I had one of those eat my lunch on trying to get the belt tension just right.
Last edited by 00pooterSS; 02-20-2019 at 08:30 PM.
02-21-2019, 07:27 AM
#12
I had a 1999 Jeep Cherokee 4x4 5 speed manual 4.0L that was my daily driver from brand new for 17 years. Had the manual serpentine belt tensioner. Hated the tensioner, but it worked. Didn't like that the jackscrew for it would corrode pretty quick, and that made for fine adjust later to be difficult. Would basically have to take the belt off of it, lube the screw, run it its full travel in both directions with an air ratchet, then put the belt back on and adjust it to the setting you want. Spring loaded is nice, but they wear out pretty quickly, lose tension, bushings wear from vibraiton, etc.....
02-21-2019, 01:43 PM
#13
TECH Addict
The Katech tensioner comes with a high wall pulley. I went from a stock size torque converter to a 91/2" converter and then I couldn't keep a belt on it. Installed the Katech tensioner and no more problems.
02-21-2019, 05:37 PM
#15
I have that 50 page alternator thread and I have been through a lot of alternator issues. On my SS the OEM alternator and the 145 amp OEM never minded going to 7000 rpm, but EVERY parts store alternator took a **** right out of the box, or the first time it saw over 6000.
On my truck the OEM 105 amp and the used 145 amp got spun to 6500 daily and never skipped a beat.
I know there is a certain point they don't like RPM, but that's all I can offer on it.
All of the above situations were with a stock diameter balancer and alt pulley
02-21-2019, 09:14 PM
#16
ModSquad
Thread Starter
iTrader: (6)
I’m running the big 2500 truck DR44 alternator, which I’m sure amplified the deceleration issue there. It’s heavy.
02-22-2019, 11:43 AM
#19
I lost a belt in my rx7 once too. I thought the bottom end let go it was so loud. The thing shredded and whipped the underside of the hood and frame which gave it that scattering sound. It was an absolute mess under the hood, but luckily didn't damage anything.
The recommended belt for my ATI balancer was too long. I kept having issues with them until I went to the next shorter belt and it has been fine to 7200 rpm. I still have the factory tensioner, but have a Katech tensioner waiting to go on my ls7 build.
The recommended belt for my ATI balancer was too long. I kept having issues with them until I went to the next shorter belt and it has been fine to 7200 rpm. I still have the factory tensioner, but have a Katech tensioner waiting to go on my ls7 build.
