serpentine belt question

I'm in the middle (well, hopefully past the middle) of installing a 302/5.0 from a '94 mustang into a '74 gt. The engine came stock with a six groove serpentine belt and to this point I've left that all intact. I have it in the car with an aftermarket a/c compressor and the stock alternator. The stock alternator is mounted on an aluminum bracket that incorporates a belt tensioner, and the alternator/bracket/tensioner is a large and heavy piece of kit. I've considered doing away with all of it and simply mounting a much smaller alternator on a custom bracket. It would save a bunch of room and a little weight. The belt adjustment would come from the a/c compressor bracket.

So, the question: obviously the tensioner is used by the factory for a reason, but is it okay to run a serpentine system without it? I'm picturing an initial period of carefully watching/adjusting the tension. After that, hopefully the belt would take a set and would only need periodic adjustment. Thoughts?

I really wouldn't try that if it were me. The Serpentine belts being very long and flexible tend to stretch to some degree and rely on the regular tension to maintain their grip. I think if you get creative you can find a way to mount the tensioner that will allow it to do its job. The belts do come in 1 inch length increments through a large range of sizes so you just need to figure the overall length you need.

You might also look at other years of the same car with different options as many have a variety of different belt paths and tensioner setups. Last you might look at a tensioner from another model car or even other maker to locate a tensioner that will bolt directly to an engine boss.(IE Cavaliers have a nice lightweight tensioner that would be easy to fab into place.

Ryan, if you're going to design your own bracket for the alternator why not incorporate the spring tensioner into the alternator mount letting it move and apply the tension to the belt. It shoud be easy to measure the spring tension of the stock tensioner with a torque wrench and then duplicate that tension on the alternator. Be careful with the waterpump direction, some are 'directional' and won't cool correctly when rotated in the opposite direction. Most of the time an earlier pump can be substituted that will work ok with the rerouted belt.

I think what you want to do would work. If you look around you might find applications that do not use a tensioner, and Gates and other belt mfgrs should have application data to give you the answer. Check with an industrial belt and pulley supplier.

Jim

I should have mentioned, the thing that got me thinking about this is the tr4 swap on the british v8 site. They are running the same exact engine, picture below. You can see the alternator mounted on the stock bracket, but for some reason they left off the tensioner. You can also see how high the alternator is mounted, which isn't a problem for me except that it looks a little dumb. My a/c compressor is in approximately the same spot at their idler pulley. Thanks for the comments, I'm really just thinking out loud...

Jim's probably right in that you probably can find a belt that'll work, but personally, i'd design a bracket that includes a tensioner. Take a look at what Larry Shimp did -- pretty much exactly what you're doing. He used a tensioner off a corvette if i recall right.

Check his write up on the V8 Newsletter...
http://www.britishv8.org/MG/LarryShimp.htm.
If there aren't good pics of the brackets there, I probably have some additional pics that may show it better. Shoot me a note if you need them & I'll check.

Rob

If you can use a tensioner it would be ideal, but Chrysler uses surp belts and Adjusters instead of tensioners on some models and I run my surp belt on my 5.0 with the Alternator as the adjuster but I don't run an AC pump.

Joe

Ryan, you can run either a tensioner or an adjuster. the belts come in the 1 inch increments as noted above. i would prefer the tensioner but my March Perf. set has a turnbuckle adj. at the alternator. Serpentine belts are easy to determine the size. take a cord, rope or other means and route around your items to be driven. once you have the measuring device correctly routed, mark the ends and cut them at that length. you then measure the total length from end to end; this is length of serpentine belt you need. the belts are sized in total length rather in diameter.
BTY, the new fuel tank arrived and i plan to begin the mods to install the GM module.
SAFETY FASTER !

Thanks for the advice guys, I'll have to ponder it a little more! :)

Ryan, Looking at the photo of the TR4 conversion, I think that is the motor for a SN-95 (1995) Mustang as I have the same motor in my MGC conversion. I think Ford mounted the alternator high like that in an effort to move it as far back as possible so it would line up with the new short water pump for that year. I believe you can fit the bracketry from the earlier Mustangs to that block although its nice to use the short water pump you get with the 95 motor. Many converters use the earlier (smaller) alternator and move it to the drivers side mounted lower down. But it may mean the longer water pump. Depends how much clearance you have to the rad. The question of the tensioner wasn't an issue for me as the '95 model used a different location than the earlier cars - low down on the run between the alternator and the crank. I would continue to use a spring tensioner if possible and only try a screw tensioner as a second choice. I'm sure both would work but the longer the belt, the more pulleys etc, the more you need a tensioner with some "elasticity" Good luck. Bob.