oldcar

1922 Fiat 501 Targa Florio

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Hey Berny, the 501 cylinder head had the spark plugs offset to the side of each cylinder, where as a 503 cylinder head had them evenly spaced which was much better for combustion efficiency and torque! There was also whats known as a Ricardo cylinder head developed before the 503 came out, which had the even plug spacing, and the combustion chamber was smaller which bumped the comression ratio up and gave a bunch more torque. I haven't heard of any plug depth differences, but haven't compared the heads myself either! From what I understand the 503 head adopted this combustion chamber design. The way to tell is the 501 head is ballooned out, while the Ricardo/503 head is chamfered over the piston (and the plugs are evenly spaced). Both are interchangable on a 501 block, but the head gasket needs to suit the cylinder head from what I've been told.

 

While im at it, the 503 oil pump has a bigger capacity over the 501 and its reccomended to be installed in conjunction with the head. You can visually tell the difference as the 501 pump has a flat base, while the 503 bulges out. Hope that helps!

 

Brodie

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Bernie,

My dad used to say 'All the world is strange cept thee and me, and sometimes I am not too sure about thee!'.

My impression of side valve heads from Ricardo is that there is a large squish area over the piston to improve turbulence and gas movement. Reading up on Ricardo's work is very rewarding, as he pioneered many important developments (eg thermostats to speed up warming), and his company is still doing leading edge stuff.

Could the thicker head have bigger coolant passages inside to improve flow? 

jp 26 Rover 9

PS Have you seen this item from 1951? Alloy Ricardo head added !

https://www.motorsportmagazine.com/archive/article/july-1951/25/modernising-501-fiat

Edited by jp928 (see edit history)

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Regarding heads, it would be great if a Silvani ohv example suddenly turned up. I believe there is one in Oz.

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Crossflow head with some huge exhaust ports! Wonder why they didn't design an individual runner system for the intake, versus using the siamesed ports?

 

Still, a really neat piece. Did he send you any pics of the combustion chambers Bernie?

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Thats a decent size drum Bernie! My rover also has 2 foot and 2 hand brake shoes per drum at the rear, but they occupy roughly a quarter of the circumference each, rather than widthways like yours. Can you advise where I might get woven linings please, as mine has bonded linings that I suspect are too hard to be effective, and I have a few hills between me and civilization ?

thanks

john 26 Rover 9

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Thanks Bernie. I will just have to keep looking....

 

jp 26 Rover 9

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Hello John

I would try some of the "out of town" Brake Repairers. You never know what you may find. 

 

Bj.

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Congrats Berny, a massive milestone! Not long now and you'll be driving it around with a milk crate clamped to the chassis like I did! 

 

As for the difference, is the left hand spring mounted back to front? The rear hanger is at a different angle compared to the right one!

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