the hobbler said:

If I remember correctly (it is about 4 years since I did the tune-up on my engine) the 126 flywheel is a bit thinner than the 500 item. Compare them before you fit the 500 flywheel onto your 650 engine.

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Well I have both fly wheels here and I fit the 500 into the 650. Problem is that the starter gear cannot reach and engage the flywheel cogs! 650 FW protrude 11mm out of the engine block surface (talking about surface that gear box bell housing attaches) while 500 FW protrude only 5mm. Do you remember if you have modify your starter so it can travel deeper and reach the FW cogs?
500 flywheel at the left of the picture.

Have you actually trial-fitted the flywheel Thomas? I would have thought that the 650 flywheel would have been more dished in the middle so that the teeth were pushed out further.
Changing flywheels has been recommended quite frequently here, so I'm surprised that no-one has mentioned this issue before or jumped up to give you the solution.

Peter as you said 650 FW has teeth pushed out, closer to starter and that is why 650 teeth are thinner than 500 FW. On the other hand as you can see in the picture 500 teeth are closer to the engine block.
I'm going to start a FW thread so we can discuss this issue with other guys that have done this modification.

So what you think about this head, in the end I brake and decide to remove head to see what's inside and put some silicon seals I had on the push rod tubes. looks like new but I have seen others with smaller chamber. Camshaft is 25/56 66/16 same as fiat 600 so I guess this is an early 650 motor.
Thomas

I hope within the week i will put the 650 engine. How about the heater duct, do i have to do any modification or replacing with another duck or i can put the 500 one?

gordinir8 said:

I hope within the week i will put the 650 engine. How about the heater duct, do i have to do any modification or replacing with another duck or i can put the 500 one?

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Many people appear to have modified the original with a bit of hammering to clear the starter connections. I found this to be unsatisfactory as the starter cable was stretched and the metal duct was very close to the electrical terminals. It might be different with the solenoid starter but when I bought the correct "R"/126-type duct I found that it had a completely different geometry as well. Its outlets point in a different direction than the 500.

https://www.fiatforum.com/500-class...ements-650-engine-i-fiat-500-a.html?p=4295717

Maybe discarding the original duct and put a flexible one all the way to the tunnel is not a bad idea. There are some silicon ones that can handle up to 150 Celsius , i think that's enough.

I wonder would a section of flexible stainless steel ducting as used as a chimney liner or some air-conditioning/heat exchanger ducting fit and work?

AL.

Poweeeeeeeeeeeer...at last. Just got my first ride with my new shiny 650 engine. I really couldn't belive that 6 more horses could make that diference. Car is nice to drive now and safer on modern roads. (now I need bigger brakes!!) Anyway a few more issues to check and little beast will be ready.