Double v-belt Alt/AC...one is loose.

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JoePole1

JoePole1

A dude in a B body
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Somewhat odd. LA 360 with PS and AC. I noticed an engine noise (not squeal of screech) at rpms over 2500 and wound up replacing my 10 year old v-belts. Problem solved. Within approximately 400 miles The symptoms returned. All is fine at lower rpms however I noticed that the outer belt on my double pulley Alt/AC/crank has a lot of play in it. You can see it kind of "flapping". Unfortunately I did not take notice on my old belts if I had the same issue but I assume it was. I still have the old belts. Both new belts look to be seated in the pulleys the same amount and I know my pulley alignment is good because nothing has been changed in many years. All brackets and mounts are solid. I was thinking of taking one of my old "stretched" belts and swapping with the new inner belt. This may give me the ability to get them balanced and see what happens. Another thought is to run a single belt (I believe I read that here) as my A.C. is not currently charged however it is on my to do list. Any thoughts or similar experience?
 
Go to a GOOD parts store and ask for a matched set. NAPA should be able to hook you up. Get a good brand like goodyear or gates.
Damn ya beat me to it.
 
I was going to be #3 with the matched set deal. Used to sell them at the parts store back in the day.
 
yes, I did also. last time I asked I was told that production is so good now that matched sets are not used. but as pointed out, maybe that only works with GOOD brands and not house brands.
 
I think dayco only sells matched belts now. Look at your new belts now,there is a batch number,check them both. I think you can request belts from the same batch, and if i recall if the number is within 10 apart they will be very close.
Swap belts front to back and see what happens.
As far as installing them,i dont put them on real tight, then run for 10-15 minutes. Re-adjust.
The slightest wear on the outside groove, a tiny amount of play in water pump bearings or a bent alternator bolt can all cause this phenomenon
 
You expect me to take advice from "The king of cobble and the master of the broken bolt?!?!?! JK.
Was thinking about swapping the new belts in their respective grooves.
 
9 years selling parts and most of my life pulling wrenches. I have seen some odd things...
 
Yes the "matched set" thing is the best advice, however, don't be surprised to get the deer in the headlight look even from a manager, because most people won't know what you're talking about. Good luck.
 
Or you could go thru their belts and look for a small number identified on the belt. That used to be the batch number and belts with the same batch were used in matched sets. Had a Gates rep tell me once that there could be up to like an 1/8” difference in length with same part numbers. If I remember correct. That’s been close to 40 years now. Of course over time they may not identify them by batch, haven’t really looked recently.
 
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I have 3 sets of belts and tried mix and match many combo's with the alt/ac/crank but still having the noise starting at about 2200rpm. Every once in a while it will go away. I was looking around under the car and noticed what looks like a 1 piece felt ring at the dampener. It is loose and I can spin it freely. Any idea what it is from? I moved it in between pictures. Thanks.
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Thanks Dicer....is it common for them to come loose? Sign of another issue? Trying to track down a noise at my pulley/ front of engine.
 
Hard to tell from the picture, but it looks to me your dampener does not have the cup to hold the felt in correctly...I would just pull it out.
 
Matched belts have always been cut off the raw stock side by side. This is how they sold "matched" sets. I am sure they are still available.
 
The thing about it is that I am getting the same results using different combinations of the 3 sets of belts I have and around the same rpm. That includes moving the inner to outer and mix and match belts. I am thinking it's not a belt issue. You would think I would get some slip and noise at start-up but only comes in above 2200 rpm. A lot less play in the belts now after tightening up alt but not overly.
 
are all 6 belts the same brand? are there any that have matching numbers, besides the size. can also do the thumb to thumb stretch and see which ones come out the same.
 
You ought to be able to push in or pull out on both belts side by side with the same force, and get the same deflection. If one moves more than the other with the same force, then they are still mis-matched. How much different they can be for deflection with the same force, I do not know a tolerance. But this source (from Gates) gives you maximum length differences of matched belt sets on page 7.
http://www.mpair.com/assets/pdf/general/v.belt.tips.pdf

If you are using used belts, then I suspect all bets are off for trying to match them by length.
 
And if the AC is not operating, why not just run a belt from the crank to the alternator, or a single belt around the AC pulley too, and not worry about the matched belts. The extra belt is there only for the AC load.
 
Thanks Mark. All of my iterations have 1 belt reflect more than the other. I tried running 1 belt alt/ac/crank with one of my new belts but get an initial screech when starting engine. It's louder than the noise that I get over 2200 rpm. I hope to get the A.C. charged soon or early next year so would like to run double belts. Looks like the consensus is matched belts just wish I knew why the problem is fairly new and is the same with old and new belts. The old belts have about 4000 miles on them.
 
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