Alternator Pulley


See pulley installation instructions below.

Dave discovered an interesting situation with his alternator pulley. He found a non-standard split-ring washer on the alternator shaft between the forward half of the pulley and the alternator body. The washer (which didn't even fit properly) had been placed there by a PO to prevent the pulley flange from rubbing against the rear face of the alternator. Following is some conversation regarding this situation.

Dave wrote - I ordered another pulley ..., so I have THREE now! And the lip that protrudes forward on the front pulley half is different on all three. The one that was on the car is the worst -- without the washer that the PO put in it would chew the alternator to pieces. The one from John Connolly (Aircooled.Net) is better, but still rubs slightly. The new chrome one protrudes forward the least and clears the alternator completely. Very strange.

Three pulleys supposedly for exactly the same application, all different. The three I have are virtually identical, EXCEPT for the depth of the lip on the front half. And that depth is critical -- if its too deep, it will rub on the alternator. The one that was on the car had that problem big-time -- the lip is about 1/8th inch deeper than the new one I'm putting on, and would have gouged a big chunk out of the alternator were it not for the big washer that the PO stuck on the shaft in front of it. (The washer didn't even fit properly on the shaft!) The pulley John Connolly sent me is better, but the lip is still about 1/32th inch too deep. I could grind it down without any problem, but its ugly! :-) So I'm going with the pretty chrome one with the shallow lip.

I'm also thinking about replacing the crankshaft pulley with a pretty one with the degrees printed all around it -- I don't know -- that's probably pretty silly. No real useful purpose -- just "tricks out" the car.

Rob responded - I guess they work okay. But DON'T get the "power pulley" version. These have a smaller diameter so they spin the fan slower, allowing a few more hp for the wheels. But of course that also means reduced cooling, so it's bye-bye engine much sooner.

Dave wrote - John Connolly (Aircooled.Net) wrote me last night to make sure I was putting both pulley halves on the alternator shaft when checking for interference -- for some reason it makes a difference. Still some slight rubbing -- I think if I take a few rough edges off with my grinder it will be okay.

I also put on the fan belt, but I'm not finished with that. I have a hard time holding the belt up so the rear pulley half goes on straight, and keep bunging up spacers! Gotta refine my technique.

Rob wrote - A new belt is always tricky. I find if I grab both "sides" just under where it will go round the alt pulley (just above the "middle of the belt if that makes sense) and squeeze it whilst pulling it up tight around the engine pulley I can hold it clear of the shims and usually get the outer pulley half on enough to start the nut.


Pulley Installation Instructions.

Note: Beware of the "tricked-out" chrome pulleys. They are an inferior product and break easily (i.e., the center portion breaks completely out). Dave experienced this problem and had to cut the old chrome pulley completely off with his Dremel.

  1. To remove the old alternator pulley, first remove the nut holding the pulley to the alternator shaft. Do this by inserting the blade of a flat-blade screwdriver through the cutout in the front half (front is front) of the pulley and brace it against the generator/alternator housing bolt to keep the pulley from turning. Remove the pulley nut with a 19mm wrench.
  2. With the nut removed, you can then remove the bell shaped spacer, followed by a number of very thin shims. Remove the outer half of the pulley, and the fan belt will come off. In-between the pulley halves, will be another group of pulley shims that adjust the belt tension depending on the number of shims used.
  3. Remove the second half of the pulley, being careful not to lose the small woodruff key that installs into a small slot in the alternator shaft. Removing the second half of the pulley with the woodruff key slot facing up, will help keep the woodruff key in place. It can fall out, be careful not to lose it, as its function is very important!
  4. Note: Don't damage your engine case and pulley by trying to remove the crank pulley with a pair of screwdrivers! It is highly recommended to use the crank pulley puller to make easy work out of it! To use the tool, you will need to remove the rear most piece of tin from the car, and, depending on what exhaust you are running, you might need to remove that as well. Remove the crank pulley bolt from the engine, and slide the crank pulley puller into position. The puller will work on a few different sizes of pulleys by sliding the arm on one end of the puller to the desired position. The center bolt will also slide, allowing you to center the pad on the end of the crank. Rotating the center bolt in the clockwise position will easily remove the crank pulley from the crank, without damaging the pulley, or engine case.

  5. With the woodruff key in position, install the front half of the new pulley onto the alternator shaft (push the pulley onto the shaft as far as you can by hand). Make sure the woodruff key is fully seated into the slot in the center shaft, and that it does not slide out of the slot while installing the pulley half.
  6. Note:If the woodruff key persistently slides out of the slot while installing the pulley half, use a very thin screwdriver to hold the key in place from the backside while installing the pulley, you may have to tap it back in place from in front of the pulley a couple times as you put the pulley half on.

  7. YOU MUST HAVE AT LEAST TEN SHIMS! Install all ten shims between the pulley halves as a starting point, and place the belt into position while installing the other half of the pulley. Install the bell shaped spacer and tighten the nut. Tightening the nut will pull the new pulley onto the end of the alternator shaft.

    Note: When working with the drive belt, make sure your hands are clean. Any oil on the belt can cause it to slip under stress.

    Note: It's absolutely critical that the belt is PROPERLY ADJUSTED. A Broken pulley is almost always the result of an improperly adjusted belt! Just because the belt tension is correct does NOT mean the belt is correctly adjusted. You absolutely MUST start with the belt too loose, and remove shims 1-2 at a time until you are at the correct adjustment. If you do not do it this way, it's very possible the pulley halves are not flat against one another, so the belt "wobbles" as it rotates, and this fatigues the center of the pulley half, which then breaks.

  8. Make sure the key is off, then rotate the engine a full revolution and check the belt tension. You should be able to push the belt in between the two pulleys 5/8", no more, and no less. If you can move the belt more than 5/8", you will need to remove shims from in-between the pulley halves, and add more if you cannot move the belt 5/8". The belt is tightened by moving the pulley halves close together, which makes the belt ride up higher, and this removes slack.
  9. Note: Remember to rotate the engine between each fitting of shims, to make sure the belt is fully seated before you check it's tightness. Always put any extra shims between the outer pulley half and the bell-shaped spacer for safe keeping for when you need to replace the belt in the future. It is VERY important that you always make belt adjustments starting too loose, then slowly tighten up. This ensures that the pulley halves are tight against one another, though they may have shims between them (this is ok). If you make the mistake of trying to rush, and do not have enough shims between the pulleys, the belt will get tight before the pulley halve are seated (and the nut is tight), and when you run the engine the pulleys will wobble and destroy themselves, the belt, and maybe your alternator. This is the most common mistake when adjusting the belt, so make sure you are patient and do it the right way to prevent walking at 3am on a rainy night. ;-)

    Note: One last tip! How far out on the pulley your belt is also determines how fast the fan spins. You can make a larger belt "work", but this slows the fan down and the engine will run hotter. Many cases of engine overheated are the result of the wrong size belt! Your engine will run cooler if you run the slightly shorter alternator belt, instead of the generator belt (they ARE different), this is one reason why the factory changed belts in mid 1973.


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