Technical Carburettor question

[dragonwagon]

Has anyone ever used a 1.25" or 1.5" SU on a 500/126 engine with any degree of success?
Seriously considering one in the general absence of Dellorto FZD's unless there's some other reasonably common alternative

 

[124BC1]

This topic was covered previously :-

Carb change | FIAT 500 (Classic)

I have fitted a 650 engine into my 500. As I am familiar with S.U. Carbs I would like to fit one. I see that some suppliers are listing a manifold to suit. Has anyone experience of this mod?

www.fiatforum.com

 

[dragonwagon]

This topic was covered previously :-

Carb change | FIAT 500 (Classic)

I have fitted a 650 engine into my 500. As I am familiar with S.U. Carbs I would like to fit one. I see that some suppliers are listing a manifold to suit. Has anyone experience of this mod?

www.fiatforum.com

Thank you for the link but it doesn't answer the question in any way, shape or form. It is mere conjecture.

 

[the hobbler]

Thank you for the link but it doesn't answer the question in any way, shape or form. It is mere conjecture.

The HS2 SU CAN be used on a 500--being that the "angle of fitment" and the flange measurements are the same, you use the inlet manifold for the FZD carb. To the best of my knowledge, nobody has come up with a definite spec for the HS2 (1-1/4 inch carb). but when I had a chat with the Burlem guys at Goodwood a few years ago (I was also looking at fitting a HS2), the best advice they could give as "somewhere to start from" was to use the settings that were in the MC2 (horizontal 1/14 inch) that was used on the Police Triumph 6T Thunderbird motor-bikes. These are:---a 'left-hand' carb (float on the left as you look down the inlet tract)--90thou Jet--M9 needle (weak needle 'MO'---'5' rich needle--spring--AUC 4387 (which I think is the red spring)--VZX1101 Needle-valve---WZX 1302 Float. As I said, these are only suggestions by Burlem as they have not made a specific carb for a Fiat since about 1938 when they did a conversion for the little Topolino (strangely---also a "500").
You say that there is a lack of FZD carbs---have you contacted "Toshi" (David Porthouse)?---he often has a FZD or 2 for sale. Alternatively, look on the Italian-e-bay web-sites---there are often a number for sale there What size engine are you going to be fitting it onto? I have fitted both 24/30 and 28/32 to a 650 engine and have arrived at sensible jetting for both of these size carbs. I also have a sensible jetting for fitting a 24/30 onto a 500. If you need help on this, feel free to contact me ( [email protected] ). Some parts are becoming almost impossible to find---I can give you the details of a Company in Italy that can supply all the jets (and they are a good quality), and I have also come up with way of getting around the "lack of throttle-spindle levers" problems (some carbs at arriving, even from Italy without these operating arms). A word of warning---there are a number of suppliers who are offering the28/32 at a VERY sensible price---if the carb does not have "Dellorto" and "Made in Italy" cast onto the side of the float-chamber, walk away from it---they are NOT genuine Dellorto. As far as I and all my "Dellorto" colleagues are aware, the 24/30 and 26/30 are ALL genuine. Lastly, connecting up the choke mechanism is a pain in the bum with the FZD---I have done away with it and just use the accelerator-pump as my "choke"---the engine will take a few minutes to run properly (until warm), but I have used this system for about 10 years now, with no problem. As I said, feel free to contact me if you think that I can be of help; or even better----have you got any friends, or relatives, who live in Italy?

 

[Toshi 975]

Did somebody call my name ?

 

[the hobbler]

View attachment 465541
Did somebody call my name ?

If "Toshi" has that Dellorto for sale, I would suggest that you contact him and "discuss a price". They are not cheap, but having used a FZD for about 11 years now, I reckon that they are about the best carb for performance for a "road-use only" car. They do not ( as the Weber carbs do) need a support and they stay in tune. Also, looking at the picture "Toshi" has put up, that carb has a 'gauzed' inlet trumpet---very rare nowadays. "Toshi" is a 'pucka' guy, and if that carb IS for sale---go for it as it is a complete set.

 

[jonny427]

View attachment 465541
Did somebody call my name ?

That would work on a standard 499cc Toshi?

 

[the hobbler]

That would work on a standard 499cc Toshi?

A 24/30 CAN be made to work on a standard 500---my colleague has done just this. I have a copy of the jets that he has fitted (and the engine runs well), although you MAY have to 'tweek' the jetting to suit your engine.

 

[dragonwagon]

If "Toshi" has that Dellorto for sale, I would suggest that you contact him and "discuss a price". They are not cheap, but having used a FZD for about 11 years now, I reckon that they are about the best carb for performance for a "road-use only" car. They do not ( as the Weber carbs do) need a support and they stay in tune. Also, looking at the picture "Toshi" has put up, that carb has a 'gauzed' inlet trumpet---very rare nowadays. "Toshi" is a 'pucka' guy, and if that carb IS for sale---go for it as it is a complete set.

A little bit out of my price range, which is why I was interested in the SU to go on a mildly tuned 652 lump.