3800 Fiero – Relocate The Alternator


Unless you managed to mount your engine extremely low on the cradle, you are likely to find that the alternator on the top of the Buick V6 3800 engine fouls the stock Fiero trunk lid preventing it from closing.  Some people modify the trunk lid, there is a spar on the underside of the lid that you can cut a notch in to provide more clearance but I chose to relocate the alternator.


Since I wasn’t overly concerned about comfort, I figured that I could live without air conditioning and came up with a plan to move the alternator to where the ac compressor was.  This plan involved deleting the AC compressor from the engine, and coming up with a new routing for the serpentine belt.  The stock Buick V6 3800 engine has two serpentine belts that run on inner and outer tracks on the balancer pulley.  The outer track only turns the supercharger while the inner track turns all the other accessories; the water pump, power steering unit, the alternator and AC compressor.  Since I was deleting the AC compressor and had no use for the power steering unit, I realized that if I made my new alternator mount line up with the outer track, I just needed to move the water pump to the outer track to be able to run a single serpentine belt.  This routing also ensures that the water pump and alternator are turned in the correct directions.

A bit more weight saving was had by deleting most of the rest of the AC hardware like the refrigerant tubes that run to the front of the car and the accumulator and tubes under the hood.

First thing to do was to remove the ac compressor, and get rid of the pulley there as well that had become surplus to requirements.  Then offer up the alternator and start thinking about mount design.

The upper mount for the alternator was a simple long bolt with a snug fitting sleeve cut to the right length to position the pulley directly in line with the outer track on the balancer pulley and the supercharger pulley.  The lower mount was made from a beefy piece of square section tube securely mounted to the engine as there is good amount of force in the belt and you don’t want it wandering around on a flat pulley somewhere.

I came up with a neat solution for moving the water pump pulley to the outer track (that I since found out has also been done elsewhere), I took the pulley off and had a good friend machine the dome off the outside face and ensure clearance on the ID … and then I installed it inside out.

In the pictures below we can see how the ‘inside out’ water pump pulley lines up with the supercharger pulley, it sits a fraction further out than perfect but looks fine with the engine running and is very difficult to modify.
We can also see the new belt tensioner mount, and the alignment of the tensioner and alternator in the second picture.  The stock tensioner was loading the belt outwards that would be trying to lift the new belt off the pulleys, furthermore the mount point had to be set so that the tensioner would apply the right amount of force with the belt in place – the running range is marked on the tensioner.

The belts seem to be available in many different lengths so once everything was in place, I simply ran a piece of string around the route but bypassing the tensioner and then measured the length of the string.  Then I took the old belt to the local CarQuest and they got the part number from a catalog and handed me the correct size belt (obviously I had to pay for it!).


Now there is plenty of clearance around the trunk and the new highest point on the engine, the supercharger snout.

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