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500 (Classic) Ducati powered Fiat from California

I have taken on the crazy task of trying to stuff a Ducati 1100 air cooled L-Twin engine in the back of my 1974 Fiat 500R, and solving all the challenges that will arise because of it!

Introduction

Hello everyone! As the title suggests, I have decided to build a Ducati powered Fiat 500!

I have restored a couple classic American cars, some motorcycles, and have designed and built a handful of Formula SAE cars in college, but I've always wanted to build my own motorcycle powered road car.

After a decade of working at one of the largest Spacecraft companies in California, I decided to take a break and try to make this dream a reality. The car needed to be simple, lightweight, relatively cheap, and older than 1975 (California smog requirements). I have a buddy that did this with an old Honda S600, and another with a Fiat 850 spider, but I wanted to do something a bit less roadster-y. Then, as the wife and I were honeymooning in Italy, I saw the answer: the old Cinquecento.

There seems to be lots of motorcycle powered 500s for hill climbing, and Z-Cars is one of the most popular swaps out there with their Suzuki Hayabusa swapped "Fiabusa" (they also make a Subaru swapped "Fubaru"), but I wanted to keep the motor air cooled (no big radiator up front) and Italian. After a bit of research, I decided to go with my favorite motorcycle engine, a Ducati 1100. The last of the big, air cooled, dry clutch L-Twins. How hilariously adorable would this car be with that noise coming out of it?

I spent a few months looking for the perfect car - something that was driveable, in decent shape, but not too nice, so I could save money up front and put it toward the swap. I ended up with a clean-ish 1974 Fiat 500 R with about 26,000 km on the clock that had been imported into the states a few years prior. The body was in pretty good shape until a strap broke towing it home resulting in a head on collision with the trailer. I minimally repaired the damaged area so I could turn the wheels full lock again, then drove it around a few months until I got the car registered.

Now that the car is legal, it's time to begin the project!

I'm looking forward to sharing the progress and hearing everyone's thoughts on the build. I have reached out to a few people individually and everyone has been extremely nice and very helpful!
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That's interesting, I haven't heard of Ducati working with Fiat on this. I know Moto Guzzi had a proposal, but ended up not going through because Fiat didn't think Moto Guzzi could keep up with demand. More about that here:



I had originally looked at doing a Moto Guzzi and VW option (would have packaged nicer) but I'm too much of a Ducati fan boy having owned 3 of their motorcycles!

You are correct, it was Motor-Guzzi and NOT Ducati----but it would still be very interesting to see how they fitted the engine and what transmission they proposed to fit. I have seen the result of a VW engine fitted into a 500 when I was at Radbourne Racing.The car was called "The Little Red Rooster" and (I think it was) 'Hot-Car' magazine did an article on it---it was not a pretty conversion---the VW enine is just plain too big.
 
Quick update before I break for some major CAD design work on the rear suspesion and differential mounting assembly

Front Suspension

I welded in the front cross braces and shimmed/aligned all the control arms. I'm petty happy with the setup, just need massage the pinch welds for clearance at full bump. I'm running about +/- 40mm of travel (limiting rebound but could go more) with about -1.2 deg of static camber. I haven't set up the steering yet (will likely make a separate post for that) so we'll see how bad the bump steer is with this setup. I'm really don't want to make custom front uprights, like I have to for the rear!

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Engine Frame

On the last update, I had just started tacking together the engine frame, but was still missing the other half, some engine mounts, and the structure to connect the two. Well, now it's all (mostly) welded! I still need to add some gussets and clean up some of the welds, but I'm happy to move on to the next portion of the build - the differential frame. This will probably take a while to flush out, since this frame will hold the differential/reversing gearbox and the suspension (control arms, shocks). I want to make sure this all is lined up pretty well since there's not a ton of room under this thing.

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Neatly done engine frame; it will be interesting to see how you build the rear-end. Couple of questions---(1) how are you going to cool the engine? In the bike instalation you have the cold air created by the forward motion of the bike helping cool it, and with the original engine installation, you have a fan and (2) How much static camber? 1-2degrees is a lot of negative camber (static) which will increase when you put weight into the car (to-wit, the driver). On my own car I have a whiff of POSITIVE camber when the car is empty and static, although I set it up with a fair bit of weight in the front of the car with '0' camber. Toe-in (again with weight in the front of the car) is best at '0', and make sure that the track-rods are of the same length after any adjustment.
 
Neatly done engine frame; it will be interesting to see how you build the rear-end. Couple of questions---(1) how are you going to cool the engine? In the bike instalation you have the cold air created by the forward motion of the bike helping cool it, and with the original engine installation, you have a fan and (2) How much static camber? 1-2degrees is a lot of negative camber (static) which will increase when you put weight into the car (to-wit, the driver). On my own car I have a whiff of POSITIVE camber when the car is empty and static, although I set it up with a fair bit of weight in the front of the car with '0' camber. Toe-in (again with weight in the front of the car) is best at '0', and make sure that the track-rods are of the same length after any adjustment.

Thanks Tom!

The bike has a small oil cooler but no fan. I plan to have a much larger oil cooler (maybe 2 if I can package them) with fans and I also plan to put a fan aimed at the cylinder heads, drawing air under the car and out the back. I may need more louvres on the rear bonnet, or just leave it off all together on hot days or days I plan to drive it spiritedly. Cooling is one of my biggest concerns, but since this won't be a track weapon, I'm hopeful I can make it work.

Regarding camber, I have -1.2 degrees static camber, which climbs to about -3.5 degrees camber under full bump. I picked the camber curves based on how much roll I expect the car to see, and wanted to minimize how much the unloaded tire goes positive. These are totally different kinematics than stock, so I could see how you might want some static positive camber to get this thing to better behave in cornering or braking, especially depending on the tires!
 
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