How much belt wrap?

Between trying to keep the engine (SBC) short to clear steering components and getting it down low between the frame rails, I have run out of room for the alternator.

If I bracket it up above the valve cover and in front of the carb I'd be good, but with a single belt there wouldn't be much belt wrap on the water pump.

How much belt wrap is needed to drive the water pump?

Anyone have pics of their high mount alternator.

 

I ran pretty much the same setup in the 48 once and another problem is keeping the belt tight enough.
I don't know if there is room enough to put an idler pulley between the alternator and pump pulleys but that might be a solution. That would get the belt to wrap around both a bit more.

 

Yeah, I thought about an idler pulley but I don't see any set ups for single V belt Idler pulleys in any of my catalogs.

 

Catalog?!?!? How about the junk yard. Almost every car out there has a self tensioning idler on it. They are for serpentine setups, but modifying one to tension the back side of a V belt should be easy

 

If you can fab up the mount, the dodge caravans use a v-belt idler
theres a few listed on this page with the sizes.
http://www.carpartswholesale.com/parts/dodge/caravan/acc-dot-_belt_idler_pulley.html

 

I would not bend a conventional v-belt on its back, they aren't designed to do that. Probably would have a pretty short belt life.

 

Back side idlers have been used forever on V belt drives. There shouldn't be a problem. I understand the idler should be on the "slack" side of the belt for best life expectancy.

 

This set-up help? Works perfectly in the blazing Florida heat. It is actually the left side brackets, reversed and mounted on the passenger side. It was originally done by the 2nd previous owner before me, and I reworked it, machined 2 new parts, corrected the spacing and alignment, and now it works excellent. I spin it up to 6500 RPM on a regular basis. Single V belt and no issues. click, this set-up gives 6" of wrap. TR

 

Mine has 3 inches of wrap. It doesn't slip but I'd feel more comfortable with more wrap. I used a curved bracket arm from Speedway, which had to be bent for my purposes. Sorry, no pics.

 

Ford successfully used a back-side V-belt tensioner in the '70s on some cars. Works fine. I had to make a similar setup on the '50 for the AC. Just don't use Dayco top-cog belts, use smooth back belts.
You don't need much more than 1/4 wrap for a water pump. I like at least 1/3 wrap for AC and alternators.

 

Paul, are you running a fan mounted to the water pump or an electric one ? If you don't have a fan on the water pump it will require a whole lot less "wrap", at least that's the experience I've had on race cars.

 

If I remember correctly, that one only deflected the belt a fairly small amount. That small amount would not add up to much more belt wrap on a good sized pulley. Going for more wrap would put a hell of a strain on the non-cord side of the belt.