Rubber belt & pulley problems---

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Caprimaniac
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Rubber belt & pulley problems---

Post by Caprimaniac »

This story starts awhile back, and there have been multiple problems.
Some 5-6 years ago I put together a GM alternator and a SBF. Low mounted, found a pully I could use, and machined a crank pully, smallest diameter possible. It has been working good.
A year ago my charging lamp started flickering, then turned on, but thank fully faded when on the highway. Last year I also managed to empty my battery at a dragrace, don't know how.....
Anyway. This year the car has worked OK. This weekend I was off to a track meet. Charging lamp had a faint light as I left, then faded.... Did some laps and then suddenly the engine was hard to turn... Low batt? Hmm. I also figured the charging lamp no longer had light when ignition on....(?)
No; after a few laps, it started good. And the Next time. Saw the RPM Counter do some strange Things out on the track, but engine ran ok.
18.00 hours and time to leave for home. NO START...... Got some cables and a running car, started up- no prob. Got into the car , driving home..... For 300m. Engine acting strange, rpm Counter jumping around. Then a sudden holt! No more battery voltage or amps... Totally drained.

So; then I was 100% sure the charging system was nonfunctioning. Time for repair or New alt. That night my old man and I drove his car 1,5 hours carrying 4 fully charged batteries to pick up my car. Paralelled 2 batteries in the trunk and fired up. Old man measured amps, and figured I could drive for 2 hours without changing batteries. It was correct; home by 2 in the night, drove With no headlights.....

Awrighty; New alt. Changed over the pulley, and got it all together. A hell of a job as I had to remove front apron and cooler to get to it.
Attempted to start the car.... With bad Luck. Was really hard to crank over. Sputtered and spitted. But- at last it fired up. And what a fire..... The garage was full of smoke in no time! My old man think he saw some sparks in the front of the engine too.
Question was where the smoke was coming from.... And after some thinking and smelling: The belt was slipping.....!!!! And yes, trying to turn the engine over showed the alt pulley to be stuck entirely.

Image

Had to do it all over over again; drain the water, remove all hoses etc. Did some cutting for clearance and had more room for alt, so the belt could be tightned and loosened in a good fashion. Did all kinds of test wit low ad high tension on the belt. Nothing mattered, it would turn some but soon hang up, and belt would spin.

The alternatorpully/ axle spins freely w/o a belt.

The alt pulley is questionable. Consists of two sheet metal pieces (don't remember what alternator/ car it came from). Orginally inteded for alt axle With dowel. It has a slight wobble, as far as my eyes can tell. It also has a Ridge Close to the rim befor the V starts dloser to the centre. I SUSPECT the belt has worn into the V and now is riding on this Ridge ( or shoulder); this is also where the belt has it's reinforced layers.... see Picture, and a wear Ridge is clearly visible....

Image

What I'm interested in is how I can choose a pulley and be sure it will fit the belt. The belt is quite wide, Heavy duty. Continental AVX13 x 725
I was thinking a v- belt is a v- belt. But not so...?

I might ahve a same length belt, but narrower.... Should I try it? yes, maybe. Easier than finding a New pulley!
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Re: Rubber belt & pulley problems---

Post by jeff swisher »

Today's V belts suck. I Hate those cogs in them.
I was getting my V belts recently from an industrial supply house.
I also tried narrow ones and cloth coated ones for lawn mowers.

The old solid V belts were in fact a tad narrower than the parts store replacements they try to sell me.

Will not hurt to try what anything at this point.. I eventually went with a serpentine belt.
Found pulleys at salvage yard and had to weld a ford pulley to a chevy to get what I want .. but looks like you could go there.
If nothing else works. And if you have room.
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Re: Rubber belt & pulley problems---

Post by Keith Morganstein »

There are Many different profiles of v-belts.

Look at opti belt. They have the best manual about v-belts, drives and components (and make the best belts). It's all here
https://www.optibelt.com/fileadmin/cont ... drives.pdf
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Re: Rubber belt & pulley problems---

Post by pdq67 »

If I remember right that through the years, the best belts were from Gates that had the cogs on the outside flat. Not the inside of the V flat.

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Re: Rubber belt & pulley problems---

Post by hpetew »

The cogs are for cooling they shouldn't contact the pulley. I've always had good luck with dayco industrial belts.
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Re: Rubber belt & pulley problems---

Post by tenxal »

If the bottom of the belt is in contact with the pulley, you'll have problems like this.
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Re: Rubber belt & pulley problems---

Post by pdq67 »

I remember back then how small/narrow my alt. belt was. It started slipping at rpm and would throw off.

I ended up going to someplace like Western Auto(?) and going though their belts. This is when I found out about automotive vs fractional HP belts. It ended up that I installed a larger dia. Z-28 alt. pulley and the right belt after I checked and found out that my alt's. front bearing was going bad.

My OEM alt. after an R&R is on my 496 now out in the garage.

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Re: Rubber belt & pulley problems---

Post by hoodeng »

As has been pointed out earlier the belt is sitting low in the alternator pulley groove and the pulley has worn flange faces ,it's these faces + tension that provide drive and must be in flat sound condition and aligned true vertically and in line .The rib construction in the inner of the belt is to aid flexibility/cooling.
A brand name belt is just that, be it Gates ,Dayco or Bosch or a number of other reputable manufacturers ,a good belt won't improve the performance of worn pulleys ,just burn out nearly as fast as a cheap belt.
When adjusting belts if you can beg or borrow one use a tool like the "Gates KRIKIT tension gauge" pn91107 ,run the new belt for five minutes after installation and re tension to spec. A forgotten service requirement from the past is that V belts were supposed to be checked for tension every oil change, [a bit like plugs and points at the same time].
When i got one many years ago i was staggered at how tight a belt is when correctly tensioned compared to what i had been tensioning to by feel for years previously .
Alternators free wheel easily on the bench but when on line draw considerable torque from the engine.
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Re: Rubber belt & pulley problems---

Post by CharlieB53 »

Even a worn belt and pulley the alternator will not lock up and stop turning. The belt will slip and overheat, but the alternaotr will still be turning NOT stopping.

I highly suspect an alternator bearing is dying, occasionally locking and again releasing and turning.

New bearings, replace the pulley and belt.

The CS series of GM alternators have long priors for killing a bearing and locking up. Many have actually started fires before killing the engine.
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Re: Rubber belt & pulley problems---

Post by BrazilianZ28Camaro »

Once I burnt a low quality Dayco alternator belt. Dayco is junk here in Brazil.

It simply couldn't handle the torque needed to spin a loaded 90 amp alternator, then I istalled a 10% bigger alt pulley and replaced the old belt with a Gates belt. Ran like a champ.

When your battery is full discharged it will put a lot of load on the alternator,you might see the the belt curving on load.

If the pulleys are worn in the V surface, or the belt is bad, it will eventually slip and burn.

Remember, new belts stretch and should be readjusted soon after install.The belt shouldn't be off the V but slight inside the edge of the V. This helps the belt to not fly out at high RPM.
'71 Z28 street strip car
Pump gas All motor SBC 427
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Re: Rubber belt & pulley problems---

Post by Caprimaniac »

Lots od good stuff here, thanks.

This belt is (was, se below...) 13mm I did try a 10mm belt, but didn't work any better.

I ended up grinding the Ridge off the flange and tighten up the belt good, and it turns. The alternator is brand New, and bearings seems 100% right.

I need a underdrive pulley.... ( Now turns 14 000 rpm at 7200 engine rpm).

IF I want to buy a pully from an Automotive Source, will it be for a 10 or 13mm belt, or will it work for both?
I did choose the 13mm belt for confidenca, and it has lasted for 5-10 years.
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Re: Rubber belt & pulley problems---

Post by BrazilianZ28Camaro »

Caprimaniac wrote:Lots od good stuff here, thanks.

This belt is (was, se below...) 13mm I did try a 10mm belt, but didn't work any better.

I ended up grinding the Ridge off the flange and tighten up the belt good, and it turns. The alternator is brand New, and bearings seems 100% right.

I need a underdrive pulley.... ( Now turns 14 000 rpm at 7200 engine rpm).

IF I want to buy a pully from an Automotive Source, will it be for a 10 or 13mm belt, or will it work for both?
I did choose the 13mm belt for confidenca, and it has lasted for 5-10 years.
I'd use a 10mm belt, it will fit the pulleys better.
Your belt must match the pulleys V size otherwise it might touch the bottom of the V and burn again, meaning do not install a 10mm belt on a 13mm pulley V.

The alt RPM sounds right for a street strip car.
'71 Z28 street strip car
Pump gas All motor SBC 427
3308 lbs-29x10.5 Hoosiers
NEW BEST ET
1.38 60' / 4.05 330' / 6.32@111.25mph

https://www.youtube.com/watch?v=99p13UK ... ture=share
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