[bhill86]

Just wondered if anyone had any insight into some belt flutter I’m experiencing.

Just finished an Original Air A/C kit install but one of the issues I’m having is the belt fluttering like crazy at around 2k RPM and up. I adjusted the compressor to line up with the crank pulley and have loosened the tension and tightened it but I’m trying not to tighten it too much.

Any other thoughts?

[Tom Vaught]

I wonder if you have all of the parts for the A/C install you are doing.
Sometimes GM would use a Idler Pulley to avoid the issue are experiencing.

You have given no information on the vehicle, engine, year of vehicle so very difficult to
help, at all, except to agree you have a problem. Much more info would help.

Tom V.

[chuckies76ta]

Originally Posted by bhill86

Just wondered if anyone had any insight into some belt flutter I’m experiencing.

Just finished an Original Air A/C kit install but one of the issues I’m having is the belt fluttering like crazy at around 2k RPM and up. I adjusted the compressor to line up with the crank pulley and have loosened the tension and tightened it but I’m trying not to tighten it too much.

Any other thoughts?

I had this issue at the track this year with an alternator belt. The belt was fluttering and was coming off after a run. I changed the pulley to a 3" to see if that would help. Lined everything up. Same result came off after a run.
A guy in the pits was looking at my issue and said Tighten that belt up!!! You have it too loose. Like you I was afraid to tighten it up too much.
So try tighten the belt up and make sure the pulleys are clean.

[bhill86]

Sorry, it’s a 400 in my 77 T\A.

[bhill86]

Originally Posted by chuckies76ta

I had this issue at the track this year with an alternator belt. The belt was fluttering and was coming off after a run. I changed the pulley to a 3" to see if that would help. Lined everything up. Same result came off after a run.
A guy in the pits was looking at my issue and said Tighten that belt up!!! You have it too loose. Like you I was afraid to tighten it up too much.
So try tighten the belt up and make sure the pulleys are clean.

Maybe I’ll have to try that

[Tom Vaught]

There is a spec for belt deflection vs a given belt span width.
Vs "TIGHTEN THAT SUCKER UP". THAT ADVICE USUALLY KILLS WATER PUMP OR ALTERNATORS OR A/C COMPRESSOR BEARINGS.
$$$$$

https://www.ibtinc.com/how-to-tension-a-v-belt/

Tom V.

[tjs72lemans]

I installed the Old Air system in my Lemans. It's an all inclusive unit requiring no idler. Maybe try a different style belt. I use the serrated style rather than the solid type. The belt may be sitting in pulley too far and causing it to stick if you will.

[Vid]

I question the quality of certain belts based on a very recent experience. I had belt issues on my ‘69 LeMans (no a/c) during Reno’s gigantic Hot August Nights car culture festival.

Doing a poker run, had an older belt break (it was getting pretty dry and crusty). Made a quick stop at the ubiquitous Autozone, replaced both belts on the spot with new Dayco belts they sold me, and I’m happily back on the road.

Within 45 minutes of cruising around, I heard something fly off under the hood, suddenly steering was gone, temp started to climb, no question what just happened, it’s the belts. I thought damn I must’ve installed them too loose. Oddly one of the brand new (lifetime warranty) belts had broken and the other belt was off the pulleys and felt unusually soft.

Went to the closet auto parts store that happened to be our local Summit store, bought a pair of AC Delco belts, installed at same tension, drove around for hours, zero problems. When at operating temperature the belts feel strong and snug like belts should, not like licorice strips. Not knocking Dayco belts but that was my experience.






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[HWYSTR455]

Auto parts store belts can be hit or miss, and there's no way of knowing how long they've been sitting on a shelf there. Just like tires, they can dry rot, and regardless of how they look, can be compromised.

I see so many people who have belts on their' rides that they have no idea of the age. 10+ year old belts are asking for trouble, it's just a no-brainer, they are wear items.

I have a dry erase board on the wall of my garage, and mark when wear items are replaced. Can't tell you how many times I comment 'I just replace that', and when I looked, it had been years.

Sadly, when I began my tribute project, during the summer, I got angry at a horse fly, and sprayed wasp killer at it. It was like a scene from a 3 stooges episode, the stream from the can arcing and right behind the horse fly as I followed it around the garage, and, sprayed the dry erase board, wiping out all the history. Thankfully, with the project, I just started fresh.

That A/C belt is pretty long, and every one I've ever seen has that 'wobble'. MAYBE, if you tighten the crap out of it, it will wobble less, but as previously stated, you can wipe stuff out by overtightening. Because the belt is so long, it actually has a different adjustment value than the rest of the belts, but am unsure of what that spec is (depends on model, etc)

One thing to check though is if there's any slop in the brackets/mounting of the compressor. It needs all the correct bushings and braces, and need to be tight. If the brackets don't hold the compressor in a solid manor, that can cause oscillation.

I see a lot of folks with pre-1970 AC the compressor 'Y' bracket gets eliminated for one reason or another (valve covers, aftermarket intakes, etc), and that will cause oscillation.

The bracket that I got from Classic Auto Air for the 442 on the adjustment side was a sleeve with a bolt welded to it, and the entire side of the compressor was supported by that one threaded rod/bolt. That thing has serious belt wobble, but it never flew off. The Vintage Air brackets are much better, got those, and it dramatically decreased the belt wobble.

But like I said, I have never seen it completely eliminated with OE brackets, just nature of the beast.

.

[bhill86]

Thanks for all of the replies. I had some time before work today a bit. Pet of my issue was the alignment of the compressor with the crank pully. I got it about as close as I think I can. I’m not overly impressed with this kit so far and the brackets are no exception.

That seemed to reduce the fluttering but I still have some. I didn’t have time to make tension adjustments yet. I’ll have to try that next.

[Tom Vaught]

First I read about this being a A/C Compressor Kit, vs Factory Components.
The Pontiac A/C Engineer put a lot of different parts into his A/C Installation Kit.
RARELY do the aftermarket kits come close to the same pulley alignments, and
compressor mount design in being rigid.

Tom V.

[Tom Vaught]

This is the first I read about this being a A/C Compressor Kit, vs Factory Components.
The Pontiac A/C Engineer put a lot of different parts into his A/C Installation Kit.
RARELY do the aftermarket kits come close to the same pulley alignments, and
compressor mount design in being rigid.

Tom V.

[bhill86]

Just thought I’d come back with a small update. Haven’t had much time to mess with much lately but rather than foot then bill for a set of VA brackets I decided to try something that was free and easy.

I have pretty rigid Edelbrock valve covers which my compressor is already super close to so I adjusted the compressor to rest on the valve cover which still maintained some belt tension and as it happens the flutter seems even further reduced. Certainly the best it’s been so I think it is more of a bracket stability than belt tension although I’m sure the tension plays its part. I may try to fabricate something to improve the stability of the compressor and maintain the ability to adjust the belt tension. I feel like a combination of a bit more tension and compressor stability may be the key. If that fails, I’ll grab some VA brackets.

Thanks again for all of the responses.

[Goatracer1]

My 1962 Bonneville came with an Old Air AC installed. It had an idler pulley but it was installed on the INSIDE of the belt which actually lifts the belt in the wrong direction. I bought just the pulley part and installed it on the OUTSIDE of the belt solving the problem. If you add an idler it should fix your problem. There are dozens of different kinds online for a few dollars.

[bhill86]

Ok, I may try that too if needed.