Just when I am trying to downsize some of my spares a pal of mine put some interesting bits on ebay. I told him I know I am crazy but I have got to have those NOS 70mms pistons and barrels which give a modest 540ccs but the piston tops are shaped to give a higher compression and the rest of the piston design is more like the later 126 than the very plain original 500 ones. Took some pics of 126 and 500 Pistons for comparison.

Took possession of the bits today at the Uxbridge motor show and showed a piston to one of the knowledgeable Fiat 500 Club members who told me that they came from one of the original Abarth conversion kits which came as a whole set of bits including badges so you could build your own official Abarth motor. Anybody got any info on this as I had never heard of a 540 kit ?

I haven't seen one for anything other than 595 and 695. Personally, I only found a full digital copy of the 595 instruction booklet. The 695 ones were too poor to read. Here's the one I have....





























cheers, Steve

Totally baffled there Toshi---the bore of a '595' is 73.5mm---I can't find any of the small Fiat engines that had a 70mm bore (Fiat 600:- 60mm; Fiat 600D:-62mm; Fiat 850:-65mm) On the Abarth variants, to go to 1,000cc Abarth fitted a longer throw crank (to 74mm) but retained the original bore. I have also checked through all my Giannini information, and they didn't use a 70mm bore either. The only variant that I can think of is the Steyr-Puch which had a 70mm bore on their first cars based on the 500D body. With a crank throw of only 64mm, it made for a 493cc engine The Steyr-Puch engine is a air-cooled boxer twin---could the pistons be for one of these engines (and if they are, could be rare, and valuable!). The Steyr engine used slightly domed pistons!!

btw, anyone know the purpose of the blanking plate in figure 7? My Italian is not so good, but maybe it's for extra ventilation to the dynamo.

cheers, Steve

Hi, I have heard of 540 kits but never in relation to Abarth. The advantage of the 540 kit is that it allows an increase in capacity without having to fully dismantle the engine and bore out the crankcase for larger barrels- the kits I saw were both piston and barrel but it may be possible to bore out the 499cc barrels from 67.4 to 70mm if there is enough material.
I'm not sure who produced them but they apparently resulted in a noticeable performance increase relatively simply.
As for Figure 7 in the Abarth catalogue that is a duct that allows the cooling air to be blown through the oil cooler section of the sump- all 500 engines should have one although it is possibly modified in the case of the Abarth to accomodate the alloy sump.

Don't you just love these little mysteries ? Let's face it they are all part of the Fiat 500 history and its evolution and worth recording. So I was initially told that the high compression Pistons gave you that desired "square" engine with a 70mm bore and stroke. As Damon says the modest increase in bore size means that you do not have to bore out the crankcase.
Now this being fresh in my mind when I woke up in the middle of the night like you do an idea came into my head. So whilst the slight raise in capacity and compression ratio would give more power to all of the engines up until the 500R if you were going to go Abarth would you not go for the 595 at least? So I wondered if this might have been part of a very early Abarth kit that might have pepped up the smaller capacity 500N engine ?
I seem to be having trouble posting pics at the moment but I will post a picture of a Styer 70mm piston for comparison

I know they're not exactly the same but VdL have always supplied 540cc pistons and barrels. https://www.fiat500vdlaan.nl/en/webshop.php?CategoryID=6

Peter you have definitely nailed it there and I had no idea abut these but as you say not quite the exact match as I can't see any depressions to clear the valve heads . On the casting inside the piston skirt it has "ASSO WERKE" and 475 on the other side. Internet check shows this as an Italian piston manufacturer that seem to have a history but I do not speak Italian so could not find out anymore.

Toshi 975 said:

but I do not speak Italian so could not find out anymore.

Click to expand...

If it helps, I use google chrome browser with auto translate turned on for looking at Italian parts/info sites. Does a reasonably good job of translating.

cheers, Steve

Steve , forgot to say how much I enjoyed looking at that booklet you posted , all very interesting. So while I was out this morning my pal sent me a link to Nanni Ricambi who are still listing these exact 540 Pistons so that closes that chapter and mystery solved. But just as one door closes another opens. I went out this morning following a lead I got at the weekend about the guy who had the original Abarth parts. I wanted to see what Pistons were in the kit and if they matched the ones I now know are from Nanni. Well they did not and here they are



Boxes not in the best of condition but they are unused and in good condition. Next thing was a nice little wooden box with "ABARTH TORINO" printed on the lid.



Boxed contained 2 piece head gasket, two exhaust valves, a set of Abarth 500 / 595 valve springs and an unused Abarth camshaft.

Well. well, you have opened a Pandora's box. I have never heard of a 540cc Abarth conversion for the 500, but if you can fit the bits without having to machine the crankcase I can see the logic of it. Coming in an "Abarth Torino" box of that size is also interesting, because when you look at the 595 and 695 kits, they came with all the bits you have (leastways, I hope you did snatch them out of his hand) plus an exhaust, badges, instrument panel, exhaust heat shield etc. so the box was normally somewhat bigger!
At thr risk of being told to 'bugger off and mind my own business' (which I fully accept--did you buy the parts and how much did you get them for--and if you didn't get them--how much does he want for them?

Hi Tom , I think that you slightly misread what I said in that I went on the mission this morning to try and see if the 540 Pistons were part of an old Abarth kit but found out on my return by e-mail that they were a Nanni part and still available.



The picture shows the two Abarth Pistons which are 499 standard size (67.4) along with the Nanni top left and Styer bottom right which are both 70mm. The box was obviously made just for the camshaft and the other parts just put in there for storage. I am amazed that they made a dovetailed jointed box just for a camshaft. I was told that there were other parts like the things you mention but they are sadly long gone. It was a bit like opening a lost tomb of treasures and I salvaged what I could.



Even the wrapping
The Pistons are stamped with the part no 63761 2

Well done for rescuing them!! It is so easy to 'just miss' these little bits of history and hear that 'oh, I scrapped them'---once they're gone, they're gone forever, totally irreplaceable.

Damon500 said:

Hi, I have heard of 540 kits but never in relation to Abarth. The advantage of the 540 kit is that it allows an increase in capacity without having to fully dismantle the engine and bore out the crankcase for larger barrels- the kits I saw were both piston and barrel but it may be possible to bore out the 499cc barrels from 67.4 to 70mm if there is enough material.
I'm not sure who produced them but they apparently resulted in a noticeable performance increase relatively simply.

Click to expand...

as far as I know, that is completely correct.
That 540ccm-sets were aftermarket-parts for early tuning...

somewhere I have a picture of one of those 540ccm-pistons. If I find it, I will post it...

Damon500 said:

As for Figure 7 in the Abarth catalogue that is a duct that allows the cooling air to be blown through the oil cooler section of the sump- all 500 engines should have one although it is possibly modified in the case of the Abarth to accomodate the alloy sump.

Click to expand...

The purpose of that shield is to reduce fan-air-loss (do you understand, I do not find the correct words) when using an Abarth Oilpan.

I have build an engine that is very close to the 595 esse-esse by Abarth using many genuine Abarth parts and did read and look for as much information as I could get. And of course I did use that shield too for better cooling...

I had a couple more pictures of the Pistons

Seems that I can only post one picture from this iPad for some reason. Also measured the camshaft lif which looks to be about 7.2mm.

My final observations on these parts show the valve springs and they actually have Abarth printed on them and the package slip that I managed to almost unfold.









Any thoughts on date as there are no clues? Also forgot to mention that the camshaft has a small dab of yellow paint on it and I seem to remember someone saying that this was some sort of colour coding but not sure where.

as far as I know, those valve springs are early D-type springs.
Later ABARTH valve springs are paintet blue and are double springs consisting on inner an outer springs...
Look here: http://www.ebay.it/itm/Molle-valvole-Valve-Springs-Ventilfedern-Ressorts-Abarth-per-Fiat-500-126-/131887753243?hash=item1eb51f681b:g:dbUAAOSweW5VKndB

I own a set of those early springs too (and some other parts. if you like, I will post) and do not mount them because I do not race my 500...