Adding a belt tensioner.

[celticwarlock]

I would like to add a spring-loaded belt tensioner (or an adjustable stationary one) to take up the slack on the alternator belts in my '69 New Yorker (with A/C). Both belts are about a half inch shorter than the factory ones so I can better tighten them with the alternator (with the stock ones, the adjustment at the alternator was basically maxed out), but even so, the great length between the A/C compressor and the alternator causes them to slip & flap a bit when the A/C is on and it's wet out.

I am pretty sure that the later 440's had a factory tensioner for this purpose, but I can't seem to find one. It's likely that I would have to adapt it to my motor anyway, but this would probably be easy enough. Failing that, I could almost certainly adapt something from a different application.

Has anybody here done something like this, and if they have, what was used? I am looking for something to put tension on the back side of the belts (a smooth, flat wheel that is wide enough to span the two belts). I already have a pretty good idea of where I'm going to bolt it in, but the wheel/tensioner itself is something I'll have to be very careful in selecting.

Any ideas?

 

[cbarge]

Speaking from experience, looking up belts nowadays you cannot rely on the aftermarket partz jobbers listings.
A lot of them hsve become generic or "fits all models" when they don't.
Take the number from your existing belts and go one size smaller..try that.
I use Goodyear Gatorback belts which are now Continental belts.
I use my Chrysler parts book and cross over to Continental belts.
They fit in the groove much better and no squeal.
You will get some slop that is to be expected and about 1/4 inch is acceptable.
Too tight of belts can and will wipe out the alternator or compressor bearings.
So no tensioner..no recomendy..lol.

 

[celticwarlock]

I don't have a problem using a tensioner, particularly one that is spring loaded, so long as I'm careful and don't have the belts "gorilla tight" to begin with.

The belts I am currently using are indeed high quality, and since they are shorter than the ones the application calls for, I have a bit of room to tighten them more, but I fear they may stretch further after I do so. In my opinion, I think a tensioner on the back side of the belts would be an elegant solution to this issue. It is not that big of a problem, as I rarely drive the car anywhere when it's wet out, but I was wondering if anybody here has tried this before.

 

[CBODY67]

I know the "harmonicing" belts look flaky, BUT there's no telling how many MILLION miles that have accumulated with that set-up.

In the EARLIER times, the a/c and alt belts were sold as a MATCHED SET to minimize the flopping around at certain rpm levels. Now, it seems you just buy two of the same part number and take your chances. More consistent manufacturing processes?

NOW, as to belt lengths . . . there are usually TWO belt widths. Yes, widths . . . .380" and .440" for the same stated length, usually. As the .440" belts are wider, they sit higher in the pulley groove than the same length .380" belt. Here's how it all interacts . . .

If the spec belt was .380" as factory production, sometimes (at least in GM), the replacement belt would be .440" wide, which meant the same belt length would not fit right. So, what I learned to do was to add 1" to the length of the .380" belt and use that length for a .440" belt. That usually worked and stopped the "Give me somethng that will fit this time" return trips by the techs. Plus the "That's what the book calls for" endless discussions! When going to a .380" belt from a .440" belt, it usually took more of the adjustment slot than before.

Chrysler did add a tensioner pulley (similar to the LA motors) when they redid the accessory mountings on the middle-later '70s B/RB motors. But to use it, you'd need to change all of the mountings and then use the appropriate belts.

I'm wondering if the rubber composition in the belts has not evolved into something different than what it was in prior times? We used to never have any issues with belts (OEM or Gates Green Stripe) slipping as long as they were properly adjusted (to a certain deflection between the pulleys). Even in wet weather. I tend to suspect that even with a tensioner pulley, the belts you have would still slip, as the total tension would be the same. Just possibly a slight bit more "wrap" around the pulleys.

Just some thoughts,
CBODY67

 

[celticwarlock]

I'm willing to try it. If it's true that the rubber compound has changed, there's literally nothing I can do about that, so I might as well try what I'm planning.

 

[Davea Lux]

If you drive the car only rarely, your pulley grooves may be rusting during the idle time. The belt riding on rust covered grooves eats away at the sides of the belts making them thinner when you start the car. The thinner belts ride lower in the groove and become loose and squeal. Check the width of your belts with a digital caliper, if they are "thin", the most economical solutions is to replace the belts. Thin belts ride at the bottom the the pulley grooves and a tension pulley is not going to help that.

Dave

 

[oldkimmer]

Also don’t forget that the pulley groves get worn after many miles. A wider belt may cure ur problem. Or u may need new pulleys. Kim

 

[BIGBARNEYCARS]

Just fab your reverse pulley bracket and elongate the mounting holes in the bracket to adjust the tension on the belts. You don't need a lot of tension on the top side of those belts to stop them from "dancing", Just a bit of tension. Been there done that and problem solved on my Hurst, Jer

 

[Ross Wooldridge]

I built a belt-keeper for my alternator that will hopefully stop the belts from getting thrown off the pulley during shifts with the AC on - a known problem for manual trans cars with AC... while I haven't tried it yet, it should help I would think.

 

[oldkimmer]

Nice. Kim

 

[celticwarlock]

Just fab your reverse pulley bracket and elongate the mounting holes in the bracket to adjust the tension on the belts. You don't need a lot of tension on the top side of those belts to stop them from "dancing", Just a bit of tension. Been there done that and problem solved on my Hurst, Jer

This is precisely what I intend, and I agree that it wouldn't take much to keep them from flopping around.