Upgrading your 500 cc engine

A lot of Fiat 500s drive with the bigger engine from the 500 R, 1st series 126 or second series 126. Upgrading your 500 cc engine to a stronger 600 or 650 cc engine is not very difficult, but you need to consider a few things.

1. The gearbox will no longer fit due to the changed location of the starter motor. The starter motor on a 500cc engine is located at the top of the gearbox. The starter motor of the 126 engine is located at the right-hand side of the gearbox.

You can either mount a gearbox of a 500 R, a gearbox of a 126 with the adjusted shorter drive shafts of the 500 or you can change the flywheel house bell. With this last option you need to consider the gearbox ratios are not adjusted to suit the additional power the bigger engine has. It will respond quicker when starting to drive, but it will have higher revs and make more noise in 4th gear.

2. You will have to change the starter motor to suit the different gearbox or flywheel house bell for a starter motor from a 500 R/126, our US1220.

3. You need to check what type of drive shafts are mounted. If you old gearbox has 17 or 19 mm drive shafts and your new one has 24 mm drive shaft you also need to change the drive shaft flanges for the correct size, which normally will be 24mm on a 500R or 126 gearbox. You will find these in our webshop as VB1010. If your 500 is a 500 N or D you need special drive shaft flanges to fit the smaller rear triangles on the N or D, our VB1093.

4. You will also need to change the following items to make everything fit:

• - KB1012 Starter cable
• - KB1019 Starter cable retaining clip
• - KB1139 Accelerator- & choke cable clip
• - VS1007 Heating tube
• - KP1046 Clutch kit

5. If you mount a 650 cc 126 engine you will no longer use the original mechanical voltage regulator. The 126 engine has an AC generator on which a voltage regulator is already mounted. You will find an instruction for this in our technical section.

6. The carburettor of a 126, Weber 28 IMB, has a fuel return line. On a Fiat 500 you need to close this return line. You can either do this with a little piece of fuel hose with a plug in it or close it directly at the carburettor by removing the brass spigot and then tapping a thread into the hole. The hole is then closed with a screw with some thread lock and a Dowty washer.

7. The engine mount on a 500 N-D-F and L is different compared to the one used on the 500 R. You will have to change the 2 studs on the engine with our MV1017 as the studs that are mounted on the engine are too long.