[T3] Serpentine Belt on a Type 3 Motor

[Gary Forsmo]

Did you do all of the "lathe work" at your home, or did you have another
location with the available lathe.

Nice work BTW for the pictures & the process of the modifications.  Did you
have to preplan the mods on a CAD/CAM?

Gary F. - Oregon WI

On Fri, Oct 17, 2025, 11:41 AM John Jaranson <john at carartbyjohn.com> wrote:

> I did a write up on the Samba about the modifications I made to Jill’s
> Type 34 Karmann Ghia in order to run a serpentine belt for the alternator
> for the electric A/C.  Thought I would share it here also.  If you were at
> the Ticonderoga Invasion last year, you saw the system in person.
>
> Time for a little update....even if it is back dated a little.
>
> Back before that last Invasion, I wanted to switch to a serpentine belt
> system to help with the belt slip issues we were having driving the 150 amp
> alternator (now 95 Amp) for the electric A/C.  Of course there are no kits
> for this conversion like there are for the upright Beetle motors....so more
> custom work.  The Type 3 motor also poses the additional challenge in that
> the crank pulley is also a fan that i necessary for the cooling system.
>
> I started out by turning a stock pulley in my lathe to remove the v-belt
> groove and the lobes around the outside.  I did leave a flange on the
> inside edge of the pulley to give me something to mate the new aluminum
> multi-groove ring to.
>
> https://www.carartbyjohn.com/JillsGhia/Ghia_Serpentine_Belt_2.jpg
>
> https://www.carartbyjohn.com/JillsGhia/Ghia_Serpentine_Belt_3.jpg
>
> Then I got sleeve of aluminum and turned the inside diameter to be a few
> thousandths interference fit to the modified stock pulley and cleaned up
> the outside diameter to make sure everything was concentric.
>
> https://www.carartbyjohn.com/JillsGhia/Ghia_Serpentine_Belt_4.jpg
>
> https://www.carartbyjohn.com/JillsGhia/Ghia_Serpentine_Belt_5.jpg
>
> https://www.carartbyjohn.com/JillsGhia/Ghia_Serpentine_Belt_6.jpg
>
> https://www.carartbyjohn.com/JillsGhia/Ghia_Serpentine_Belt_7.jpg
>
> https://www.carartbyjohn.com/JillsGhia/Ghia_Serpentine_Belt_8.jpg
>
> Then I parted off the appropriate length and end up with two parts that
> now needed to be shrink fit together...
>
> https://www.carartbyjohn.com/JillsGhia/Ghia_Serpentine_Belt_9.jpg
>
> https://www.carartbyjohn.com/JillsGhia/Ghia_Serpentine_Belt_10.jpg
>
> I made a simple wooden fixture to hold the pulley, through it in the
> freeze and the outer ring in the oven for an hour or so.  Dropped the
> frozen pulley into the fixture.  Dropped the hot ring over the pulley and
> clamped it all together to let it come back to ambient and lock together.
> Worked great!
>
> https://www.carartbyjohn.com/JillsGhia/Ghia_Serpentine_Belt_14.jpg
>
> https://www.carartbyjohn.com/JillsGhia/Ghia_Serpentine_Belt_15.jpg
>
> https://www.carartbyjohn.com/JillsGhia/Ghia_Serpentine_Belt_16.jpg
>
> https://www.carartbyjohn.com/JillsGhia/Ghia_Serpentine_Belt_17.jpg
>
> Next, I had to make a cutting tool that matched the profile of the grooves
> for the serpentine belt.
>
> https://www.carartbyjohn.com/JillsGhia/Ghia_Serpentine_Belt_18.jpg
>
> https://www.carartbyjohn.com/JillsGhia/Ghia_Serpentine_Belt_19.jpg
>
> https://www.carartbyjohn.com/JillsGhia/Ghia_Serpentine_Belt_20.jpg
>
> Then I machined the profiles into the ring and cleaned it all up.  I
> transfered the timing marks to the outer diameter of the pulley (this is
> one thing I still need to improve by transfer the marks to the outside edge
> of the pulley so you can see them easier through the timing hole).  The
> pulley mods were done.  Not just need assembly...
>
> https://www.carartbyjohn.com/JillsGhia/Ghia_Serpentine_Belt_21.jpg
>
> https://www.carartbyjohn.com/JillsGhia/Ghia_Serpentine_Belt_22.jpg
>
> https://www.carartbyjohn.com/JillsGhia/Ghia_Serpentine_Belt_23.jpg
>
> https://www.carartbyjohn.com/JillsGhia/Ghia_Serpentine_Belt_24.jpg
>
> https://www.carartbyjohn.com/JillsGhia/Ghia_Serpentine_Belt_26.jpg
>
> I did have one other mod I had to make.  The idler pulley for the
> serpentine belt had larger ID than the old v-belt idler, so I turned a
> bronze bushing to make up the gap.
>
> https://www.carartbyjohn.com/JillsGhia/Ghia_Serpentine_Belt_29.jpg
>
> https://www.carartbyjohn.com/JillsGhia/Ghia_Serpentine_Belt_31.jpg
>
> Assembled onto the motor with all the tin in place.
>
> https://www.carartbyjohn.com/JillsGhia/Ghia_Serpentine_Belt_33.jpg
>
> https://www.carartbyjohn.com/JillsGhia/Ghia_Serpentine_Belt_34.jpg
>
> The system works great.  I might try finding and fitting a sprung belt
> tensioner idler pulley, but for now the static tension adjustment at the
> alternator brackets seems to be just fine.
>
> We now have well over 6000 miles on this version of he system after the
> 4500 miles we just put on going to Las Vegas and back.  We have had no
> issues with belt slippage or the pulley mods.  The A/C system still blows
> plenty of cold air.  We used it for 4 hours straight one day on the drive
> out to Vegas and it kept the Ghia nice and cool and comfortable.  It was so
> much nicer driving with the windows up where Jill and I could actually have
> a normal conversation in the car.
>
> John
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