Why is my alternator belt strecthing?

Discussion in 'Street/strip 400/430/455' started by skylarkroost, Jun 5, 2006.

  1. skylarkroost

    skylarkroost skylarkroost

    Finally got the A/C compressor (correct one) and all the correct pulleys and brackets on the car, so now the A/C works great but for some reason the alt. belts keep stretching and seem to be shrinking in width. The A/C belt does fine just the alt belt has issue. Has anyone else ever dealt with this problem? Is there a correct width belt that maybe I'm not getting? Help please guys I really want to drive the car to Indy instead of trailering but this could keep me from doing that unless I can resolve it.
    Thanks in advance.
     
  2. Yardley

    Yardley Club Jackass

    I believe the GS/Stage1 option has a narrower and deeper pulley to prevent throwing the belt off at higher RPM.

    Can anyone confirm?
     
  3. 462CID

    462CID Buick newbie since '89

    :confused: I've been driving a '70 Skylark as a daily car since '89 and I never had an alternator belt stretch even once. I had a few that were simply worn out and I threw one once, but that's about it...you say the width is actually visibly changing? I can't see how the a/c ingluences this, but was this problem around before you had a/c hooked up? Have you considered taking off the a/c belt and then seeing if the problem arises? In any case you need a new alternator belt in my opinion.

    What brand alternator belt are you using? have you tried just replacing it? Maybe it's defective. maybe it's getting coolant on it from a small leak you haven't noticed

    This is a problem I have never heard of before. I certainly don't know all but I would suggest seeing if taking the a/c out of the picture helps. Are you sure you have the belts on the right pulleys and that everything lines up?

    The belt shouldn't be that elastic...you should see fraying and wear before stretching in my opinion
     
  4. 65specialconver

    65specialconver kennedy-bell MIA

    poo poo parts

    ive seen it with the off brand belts. :mad: different rubber compound than the u.s.a. made stuff.with everyone going to the multi-groove,suppliers are buying the not-so-popular belts from overseas.find one made in the us.as far as width,it should be 3/8.if the stage1 option used a narrower belt,the crank pulley would be different also.even so,it shouldnt stretch.i assume your not talking about the common break-in readjustment stretch.
     
  5. I had this happen with an alternator belt on my Wildcat. The thing would keep stretching so I would keep tightening the alternator. It was driving me crazy because every week I went to start it and the belt was flopping around again. I was checking planes and pulleys and waterpumps, and everything seemed okay. One day the belt snapped, so I put a new one on there.

    Never had a problem since.
     
  6. tlivingd

    tlivingd BIG BLOCK, THE ANTI PRIUS

    your putting it on there loose right? meaning your not having to roll the belt on with a screw driver are you? If you twist a belt, or it's tight going on over the alternator pully where you need to turn the pully to get it on, there is a good chance you'll break the cords in it and it will just keep on stretching till SNAP.
    I know mine is a PITA where I in some cases I would have to roll it on. (my alternator dosen't swing close enough to the water pump :Do No: ). I've found on my 350 to use the "correct" belt I have to loosen the bolts on the water pump pully to allow it to deflect some then tighten the pully bolts back up again then tighten up the alternator.
    -nate
     
  7. Ken Warner

    Ken Warner Stand-up Philosopher

    Little recent experience

    Have used Kelly belts (autozone) since I put my GS together about 8 years ago. When I put the new AM+P engine in I put all new Kelly's on and put the old ones in the trunk for spares. I kept tightening the AC belt til finnaly I found it twisted. Decided to try the good ol Dayco belts I used in my SBC days (WAY more RPM's and never a problem). Same part number belt but it fit a bit looser and sat deeper in the pulley grooves. Went back to re-tighten last weekend and no need.
     
  8. skylarkroost

    skylarkroost skylarkroost

    Ok, first belt was an advance cheap brand because they didnt have a Dayco that size in stock. I don't have to "roll" it on the pulley. The generic one got loose after about 4 hours run time, typical time to retighten a new belt to allow for intial wear in. BUT then in another 6 to 10 hr. run time (rough guess) it started squealing again. Tightened it again. Same thing in an even shorter time. Noticed black rubbery flakes on bottom side of hood in line with belt. Finally it broke. By this time I had bought a Dayco else where. So far I just had to do intial wear in tightening. The A/C belt has never been retightened after intial wear in tightening and is still fine. No squealing when I turn on the air either. Today I notice a really dim red light in the GEN light. Is it possible the alternator (which is less than 6 months old) is turning hard enough to cause this? One other note is that my A/C belt ride just barely above the bottom of the rear alternator pulley. I've seen some that rode in the same place but some almost an inch or better over the top of the pulley. I have the correct oversize pulley on the compressor too. Any thoughts?
     
  9. copperheadgs1

    copperheadgs1 copperheadgs1

    Eddie, 70 455 Ac belt should clear the rear part of the alt pulley by a good distance maybe an inch or more. Sounds like something in the system is wrong year part. Maybe lower comp. bracket or alt bracket. 71-72 ac belt touches rear of alt pulley. Also Gates belts are very good. MAde in USA and don't stretch. Can you post a couple of pics. front and side views?
     
  10. 65specialconver

    65specialconver kennedy-bell MIA

    any chance any of the pulleys are worn excessively?you also mention a dim alt light,which would cause the alternator to work too hard creating more of a load,but shouldnt effect the belt unless its slipping.all it takes is a tiny ding in a pulley to eat belts.
     
  11. defan238

    defan238 Well-Known Member

    are the pulleys out of line? grooves pitted? try by hand without belt and spin alternator to check bearings when alt is cold and hot ,also taking note of the resistance while turning.cack all grounds and battery conections to make sure you are properly charging so that you are not overworking alt then causing your belt problem.
    ed
     
  12. skylarkroost

    skylarkroost skylarkroost

    I'll work on these recommendations tomorrow and see if I can come up with an answer. Thanks guys, I'll get back and let you know what I find.
     
  13. 462CID

    462CID Buick newbie since '89

    Describe exactly when the GEN light comes on, and how bright

    The idiot light actually has four conditions (on, off, full bright, half bright) and will tell you a good amount of info
     
  14. skylarkroost

    skylarkroost skylarkroost

    Chris, Its just barely visible. Very dim would be the best description.
     
  15. 65specialconver

    65specialconver kennedy-bell MIA

    if its the internal reg type its a diode trio.local rebuilder can sell you one for a couple bucks.id offer,but shipping would be more than the part :pp
     
  16. skylarkroost

    skylarkroost skylarkroost

    Ok, update on this prob. The Gen light was simply the fan belt loose enough to flop (although it wasn't squealing). Tightened it back up and light went out. However the Dayco belt is doing the same thing. I don't know for sure but I think the alternator is sitting cockeyed from the rest of the components. Here are some pics that show the setup. First pic shows crud from belt on carb.
     

    Attached Files:

  17. skylarkroost

    skylarkroost skylarkroost

    View of pulleys
     

    Attached Files:

  18. 65specialconver

    65specialconver kennedy-bell MIA

    in your second pic,i think i can actually see the belt tapering to the inside.something isnt aligned.are you sure you have the correct brackets?short of that, there are shims that go behind the alt fan for worn spacers.i use them on generator to alternator conversions when someone fabs a bracket.once again you should go to your rebuilder and get a couple.no more than that.it will place the pulley farther out.
     
  19. copperheadgs1

    copperheadgs1 copperheadgs1

    Eddie, is that a parts store rebuilt alternator? The bottom holes on these are always egged shaped for some reason like the rebuilder reams them or something. This causes the thing to sit everyway but straight. I have also had this problem until I found an original unmolested alt out of a junked car and had that rebuilt. If you loosen the bottom bolt and eyball it straight then tighten bottom bolt it may work but it is tough.
     
  20. 65specialconver

    65specialconver kennedy-bell MIA

    thats true,in mid 1977 they went metric,a bit larger than sae.every rebuilder on the planet drilled them out for both 3/8 & 10mm applications.some put a thin removable sleeve in the hole to take up the slop.virgin housings are far & few between.
     

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