[DeTomaso] FW: Custom pulleys

[F&D Terry]

There is ample room to run a 10 ribbed belt without relocating the 
engine. I did so with a supercharged engine in a '72 and '87 Pantera. 
There is no hazard of running any accessory in the wrong direction if 
the ribbed side of the serpentine belt is the contact side. All driven 
pulleys should be grooved pulleys so the ribbed side of the belt will be 
the contact side. Aluminum pulleys are not weaker than steel when used 
in a serpentine belt application, however, I strongly recommend they be 
hard surfaced. The governing factor in any pulley application is the 
speed at which the pulley is driven. Cast iron pulleys should be 
balanced if their speed is excessive but aluminum will tolerate much 
higher speeds. Very few cast pulleys are in use today since the casting 
process is very expensive when compared to CNC formed pulleys. Some 
companies supply cast ribbed pulleys suitable for timing belts but they 
are in small diameters and of no practical value since most must be 
mounted on special hubs.

I have said many times that there is nothing to be gained over the stock 
vee belts by running a serpentine system. To install a serpentine system 
properly requires that a tensioner be added to the slack side of the 
driver pulley. A serpentine belt can easily "grow" over 1/2 an inch 
under load so when incorporating an A/C compressor it is best to use a 7 
ribbed belt, with 8 being a good choice. All pulley diameters should be 
a minimum of 3-1/2" in diameter to reduce belt fatigue. The Gates Rubber 
Co. offers some very good design manuals covering all types of drive belts.

Take a look at http://www.bcpl.net/~gt5s/drive_belts.jpg. The drive 
system for the lower belts uses a 10 ribbed serpentine belt, a stock 
V-belt and a 1/8" notched timing wheel and does not require the engine 
to be moved rearward. The upper belt is 14 ribs wide. Both drives use 
automatic tensioners and run flawlessly. The back cover of POCA profiles 
issue 2004 #4 offers a better picture of the complete installation.

Fred T.

David & Marilyn Bell wrote:

>Forwarded from Jack DeRyke:
>
>-----Original Message-----
>From: JDeRyke at aol.com [mailto:JDeRyke at aol.com]
>Sent: Saturday, May 05, 2007 3:06 PM
>To: DeTomaso at realbig.com
>Subject: Re: [DeTomaso] Custom pulleys
>
>A few thoughts- because the belts are wider, you may need to shift the
>engine
>and ZF backward a little to clear the firewall and access cover, and
>remember
>when running a flat or toothed-belt drive, the accessories may be driven
>backwards depending on the design. Some waterpumps and most alternators (due
>to
>the mount of the brush in the back) are designed to run in one direction, so
>this may increase the expense if you convert, but does save the complication
>of
>buying & changing pullies on the accessories if they're all-new. I think
>rotary
>A/C compressors are OK spinning either way. A few mfgrs use
>cast-and-machined
>aluminum pulleys which can be significantly weaker than steel, or aluminum
>pulleys made from plate. Some older cast/machined flat-belt pulleys have
>cracked
>in use- usually leaving the Pantera dead on the side of the road unless one
>carries spares & tools. This's one reason why I made my own- no one could
>guarantee the available alloy pullies were strong billet. Good luck- J
>DeRyke
>
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