General Camshaft for 500N

[TeleSpeed]

Greetings!

I am starting the restoration of my 1959 500N Jolly and am having the engine rebuilt. Rather than increase the case opening to accommodate a larger cylinder, I plan to reuse the original 479cc cylinders and fit new 66.8mm pistons that I already have. The question I have is concerning the camshaft. I was planning to install a new camshaft that can provide better performance (nothing too radical). I was thinking about installing an original Nuova Sport camshaft, but I can't find one. Nanni Ricambi have two different options for a 500N camshaft, a 75/35 - 35/75 and an 80/40 - 40/80. However, those numbers are not even remotely close to the Sport Specs in my original 1959 factory workshop manual 25/51 - 64/12. Perhaps I am not interpreting the differences correctly. Knowledgable advice would be appreciated.

Eric

 

[Bleeding Knuckles]

Greetings!

I am starting the restoration of my 1959 500N Jolly and am having the engine rebuilt. Rather than increase the case opening to accommodate a larger cylinder, I plan to reuse the original 479cc cylinders and fit new 66.8mm pistons that I already have. The question I have is concerning the camshaft. I was planning to install a new camshaft that can provide better performance (nothing too radical). I was thinking about installing an original Nuova Sport camshaft, but I can't find one. Nanni Ricambi have two different options for a 500N camshaft, a 75/35 - 35/75 and an 80/40 - 40/80. However, those numbers are not even remotely close to the Sport Specs in my original 1959 factory workshop manual 25/51 - 64/12. Perhaps I am not interpreting the differences correctly. Knowledgable advice would be appreciated.

Eric

Hi Eric, Although not particularly relevant I have modified two engines using each of the cams you quote. The first using the 75/35-35/75 gave a solid 36.2 bhp at the flywheel @ 5000 rpm this engine was enlarged to 712cc using 80.5mm pistons. The second using the 80/40-40/80 has not been tested (covid) , but exhibits more power with 704cc and 80mm pistons, the point here is that both engines are now showing the power increase much further up the rev range making them more peaky. I would try to find that elusive sport cam or see if you can get something close re-ground.
Ian.

 

[Toshi 975]

I have an original 1960’s genuine Abarth camshaft that was described as fast road/rally. It is new but I tested it for 800 miles in a tuned engine and it worked very well.

 

[TeleSpeed]

Thank you for the feedback Ian and David. Regarding the Abarth cam that you have David, what are the specifications? Does it have the correct size drive sprag slot for the Nuova oil pump?

 

[the hobbler]

The 35-75-35-75 is the 'softer' of the 2 cams that 'Nanni Ricambi' are offering. If you can't find a geniune 'Sport' cam,that is the one that I would go for. The original 'Sport' cam doesn't have a great deal of overlap. Toshi's cam might be the answer for you, as long as the drive sprag matches with the oil pump. The only other alternative is to have a word with either 'Kent Cams' (who do cams for Middle barton) or 'Newman Cams' and have your cam built-up and reground to match the old 'Sport' specifications. Both the above mentioned companies have very good reputations.

 

[the hobbler]

Sorry, forgot to mention--when you rebuild the oil-pump, fill it full of Petroleum jelly (NOT grease) prior putting it all back together---it gives the pump something to suck on when initially cranking the engine over, and will help give you oil pressure quicker.

 

[Toshi 975]

Thank you for the feedback Ian and David. Regarding the Abarth cam that you have David, what are the specifications? Does it have the correct size drive sprag slot for the Nuova oil pump?

I do not know what the camshaft specification is all I can say is that the guy I bought it from some years ago described it as a fast road / rally cam and not a more extreme racing camshaft. He said that he raced a Fiat 500 back in the 60’s and he kept a selection of new spares in case of a breakdown as was born out by the fact that he also sold a collection of Abarth parts on eBay and I was lucky enough to win the camshaft. I can tell you that it has a lift of 7.3mm on the lobes. I once tried to check the specification of the Alquati camshaft I had but I got in a total mess and gave up. I also had a sport camshaft that had been fitted in a 595 Italian prepared Abarth replica and that had a 7.65mm cam lift.
I have been measuring 500 and 126 oil pump drives and what you call the sprag, I call it a dog drive, and the slot in the camshaft is definitely a fraction smaller in the Abarth camshaft I would say by a fraction of a millimetre. I can’t get my callipers in there to measure it. I would say that the slot is about 7mm as opposed to 7.4mm on later versions.
I have come across this situation in the past when assembling engines and always check the fit and if necessary just carefully grind a fraction off the oil pump.
I am also expecting a 35/75 camshaft to be delivered soon which will be spare as it is coming with a collection of tuning parts I have purchased.

 

[TeleSpeed]

David, the Abarth camshaft is sweet. I'd really love to have it, but it is my understanding that the dog drive on the N and D oil pumps fit into a 6mm camshaft slot rather than 7.3mm (if anyone can verify or correct this understanding, please advise). Also, without the full specs, it is difficult to determine if the cam will be too hot for the 479cc engine. If you get more specific info in coming weeks, please let me know. Tom, thank you for your excellent guidance.

 

[the hobbler]

Yes, the early engines had smaller drive 'sprags between the oil-pump and the camshaft. In order to use David's (Toshi) camshaft, you might be able to fit a 500 (NOT a 126) oil-pump into the timing-chain cover--they can be bought seperately and are not very expensive.