I’ve been on a wild goose chase of sorts tracking down components to build up my 36hp motor for the Frankfurt Flyer. Thanks to the help of two fellow Porsche Enthusiasts, David Bisiri and Land Speed Record holder and fellow VW/Porsche NUT Tom Bruch I’ve been able to speed up the process of finding out what’s compatible with this engine and what doesn’t work.

Many purists may raise their nose to the idea of using Porsche parts in a VW motor but for me, I love experimenting and learning how to interchange components, modify them and make one hell of a motor. That said, Here’s my engine blue print for the bottom end:

What you see in this picture is a 1958, 36hp Volkswagen engine case. 36hp cases are easily identifiable by the oil filler/generator stand that is cast into the case, similar to early Porsche motors.

The cylinders are the original 36hp 77mm size. I was having a heck of a time deciding what to do with my piston/liner setup. More about that later, here are the piston liners (they turned out great!):

Deciding on using the original pistons/cylinders was tricky. I want this little stroker to move and have a good compression ratio. What Tom clued me in on was the fact that 66 Bug (1300) motors have the best pistons available for this motor and they slip right in without any modification to the original 36hp liners! The bonus shown in the following pictures is that there is significantly more product at the top of the 1966 Bug pistons than the earlier models which allows me to dome them for better compression!

The Piston at left is the original 36hp, you can’t see it from here but the design of this piston leaves very little “meat” at the top making it impossible to put on a lathe and dome. We feel that this would end up in a blown piston. The middle piston is the 1966 version. Notice the wrist pin is the same size as the piston at right (Porsche 912). This allows the 66 piston to slip right onto the Porsche connecting rods. The middle piston is also domed on the inner casting, giving it significantly more material at the top which allows me to throw it on a lathe and dome it, like the Porsche piston at right. As for wrist pin placement you can see they are all three different heights. I will have to use spacers or shims to boost the top end out for clearance.

The rods I’ve chosen, as mentioned above are the Porsche 912 rods. These will work well with the 74mm Stroker 912 Crankshaft Pictured here:

The 912 Crank will be “turned down” on two of the mains. This means that the thickness of the metal at the main bearing points will be removed as to fit into the VW 36hp case. The stock mains for the Porsche are 55mm and the VW is 50mm. So, in theory 5mm will be removed. We will dial this in precisely at the crank grind shop. Here are the VW and Porsche Cranks side by side. The Porsche Crank at top and the VW Crank below. You can see the size is greater of the Porsche crank, this is why the engine will be referred to as a Stroker.

As for the cam, I will be using an original Iskenderian 2-J or “Isky” cam. This gives a nice lopey lift and great power all the way through the range. Tom is the current custodian of the cam and I plan on picking it up next week.

The conservative estimated HP for this set up will be 70hp. I will update on the heads and carbs next. Stay tuned!

Tags | Homebuilt Racer, Porsche, Vintage Speed, Volkswagen