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Over the years, fellow 356 owners and i've used some or all of the following with complete success: Gates 665, Gates 676, Goodyear 5373, Dayco 831X, Dayco 5373.

My '47 Super Clipper has a cogged Gates belt with a green stripe around the middle of the outside circumference, can't see a model #.
I've run it for years, a-ok.

However, after replacing my water pump pulley with a virgin spare which i first sanded, painted and baked (old trick, 180 degrees or so in the oven for 10-15 minutes makes painted items vastly tougher), i'm
getting belt noise.

(My existing water pump pulley had a harmless fingernail chip on the firewall side which harmed nothing but y'all know how these cars can bring out your inner Adrian Monk. That, and i decided to strip, buff and clear coat the factory steel fan blades so they'd look aluminum like the older Packard engines. Strictly a cosmetic thing i like, had the new pulley and fan balanced at the machine shop.)

I can soap the belt, another old trick,
but i'm thinking i should use my NOS Gates smooth belt (non-cogged) for the hell of it.

Are we right that in the day, all these fanbelts were smooth, and the cogged belts came later, much later, aftermarket?

And, what was the rationale behind a cogged belt? Cooling? Hard to fathom that, because the cogged portion is only the inner, bottom of the fan belt, which doesn't contact the trough of the pulley.

Finally, anyone ever hearing of a 356 fanbelt wearing out, let alone breaking? Stoutest fanbelts we've ever seen. A friend who still uses a '37 Caterpillar to fireguard his property twice a year says the Packard 356 engine fanbelt's stouter than the one in his Cat. It's
over half again thicker than the ones in friends' '41 Cadillac-ack-ack-ack-ack-ack-ack-acks.

Any insight into all the above?

Cogged belts generate less internal friction especially when turning around tight radii and less heat generated within the belt equates to longer belt life. In a cogged belt all the strength cord is in the upper/non cogged section so they are more flexible than the old style.

Yes, I've seen a couple of broken 356 belts but they were VERY old and not much elasticity left in them I guess. Back in the 60s a common replacement for the 356 belt was Gates 85T or 86T and later an 880T which were truck & bus belts also used on GMC, White, and others.

One reason for the cogs is increased flexibility when used with smaller diameter pulleys. I believe they also tend to run a bit cooler and I expect the fact that some amount of material can be eliminated so less cost to manufacture also comes into play.

There are a few videos on belt properties where the cogs are touched on. Here's one.youtube.com/watch?v=zH1RRx2j9SM

You can get a proper sized belt from John Ulrich, just up the Damn Road in El Sobrante. I tried a couple of NAPA/Gates belts, but finally broke down and got the right one from John. It is not inexpensive, about $50, but a quality item. It is difficult to install because of the deep pulleys and wide belt width. I know a couple of people who could not get their Ulrich belt installed and sent it back. I prevailed.

(o{}o)

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It CAN be tough to get that belt on, especially if the front motor mount has sagged enough to leave too little space between the crank pulley and the frame cross member. Also, if instead of moving the generator to it's innermost position on the adjustment strip you completely remove the strap, you can get the generator a bit more inwards and that often makes a tough job much easier.

Friends

I put a belt on my '41 160 two years ago. On these cars one has to wedge it between the lower pulley and frame on the RH side. After about 2 hours of 4 people working on it, I had an idea . We smeared the belt with silicone and pushed it through the gap with with a stick about 3 feet long.

Regards


John Harley

Thank you , college of cardinals. Now all that remains is to figure out w h y i'm getting belt noise when using this same Gates "Green Stripe" cogged belt for years before i never heard a sound. As above, i replaced my chipped water pump pulley merely as it had a small chip, a cosmetic flaw only, with another 356 water pump pulley i already had on hand, tho' virgin. Before installing the pristine water pump pulley, i sanded and sprayed it black, several coats, including inside the vee, which a wise auld car friend says was a mistake, i should've left the inside of the vee unpainted.

Can't imagine just having new paint on the replacement pulley vee would cause the new noise, but what else could it be?
Again, i baked it in the oven as i do all small parts, so the finish is nearly as tenacious, durable as powdercoating.

Can smooth, slick paint in the vee account for the noise?

Have any of you noted cogged or smooth belts being quieter? I wouldn't think it'd matter since none of the various 356 fanbelts mentioned above contact the trough of the water pump and generator pulleys.

Welcome any insight before i hassle trying my spare NOS Gates 665 smooth belt, getting the adjustment just right.
Too tight is murder on water pump and generator bearings,
but neither do i want either belt slipping.

My car also never made a sound.When I changed the water pump, I bought a John Ulrich replacement belt because mine had a nasty split in it.From the time I put it on until now, the belt would scream.I put fan belt dress on and that would quiet it for awhile but the noise always came back. I was fortunate enough to get an old napa belts without the cogs and the car is now quiet again. I know many people who have used John's belts and have never had a sound. Cannot explain why my car was different. See if you can find one witout the cogs and give it a try.

You might check the alignment of the pulleys to see if they are all in the same plane. The water pump pulley location is determined by the correct positioning of the hub (pressed on).

Thank you, gentlemen. The spare water pump pulley is identical to the chipped one i removed other than it's gleaming new smooth paint, so everything
remains aligned as before. Again, as the cogged underbelly of the Gates "Green Stripe" belt doesn't contact the trough (bottom) of either generator or water pump pulleys, only their veed sides according to Hoyle, i
can't divine this #!*&@!# noise.