This is what I made to fix the problem once and for all. Notice that I have almost 180 degree wrap on the alternator pulley and almost that much on the drive pulley.

The spring keeps a constant force on the belt as it stretches and wears in. The alternator is locked at mid point of its travel so there is room for adjustment both directions.




It is a very easy installation using just two bolts that you can actually get to with out dissembling half the car. The belt is 4 inches longer than the original.




Here are the parts that I made from some metal I had laying around. I purchased the main roller bearing and two smaller rollers for the swing arm.

I have about ten hours of labor (fun) in it.

Ray

Cool! A completely home-made belt tensioner. Great for early Duke folks. Dodgerunner made a similar mod for V6 cars, but his mod uses a commercially available tensioner. He made the brackets to fit it to the engine. Check out his here.

Nice mod.

I had the same problem with my 4cyl. The reason was that I was missing some of my alternator bracket to block bolts missing. You might want to check them.

Thanks TopNotch I checked out his site and his looks great.

Thanks again
Ray

I love this forum. Plenty of ingenuity and talent. Plus lots of help when you get to the limits of your own ingenuity and talent. Now we need one for 87-88 dukes.

*edit* for rating PFF member Positively on the basis of ingenuity and inventiveness.
------------------
John
1955 Chevrolet 210 Sedan (Sitting idle for the moment)
1988 SE seized duke... next engine... L81?
1988 CJB T-Top (Project car) # 385 of 1252
2001 Saturn LW300 (Daily driver until CJB done)
2001 Saturn SL1

[This message has been edited by FieroCustom (edited 03-23-2009).]

quote Originally posted by FieroCustom: Now we need one for 87-88 dukes.

Um.... 87 and 88 dukes already have a tensioner.

This is a great piece of fabrication work.

As a nerdy engineer, I do have to mention that V-belts are not intended to be bent "backwards" and the increased strain and tension in the fibers at the bottom "tip" of the V will cause a shorter belt life.

This is actually the reason for the invention of the "multi-rib" or "serpentine" belt, is to be bent in both directions. Serpentine belts have lots of "little Vs" that have an equivalent surface area for contact but are not as thick so the outermost fibers don't see as much stress.

Ok, let me clarify, yes, 87-88 dukes have a tensioner, an over priced one... I was thinking it would be nice to have a cheaper replacement than what I had to pay for mine. Thinking of things to improve, I should give TopNotch a + for his ultimate slave idea.

I have been wanting to build one for the duke but have never had an engine available to build one from.

Nice job though..