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Discussion Starter #1 (Edited)
I have got the impression that the engine differences between the 4 types (excepting the Corsa)are limited to piston changes (to alter CR) and the number of carbs fitted.
Fusi gives these figures:
6C2500 Turismo CV [email protected] CR 7.0:1 Carbs 1
6C2500 Sport CV [email protected] CR 7.5:1 Carbs 1
6C2500 Supersport CV [email protected] CR 8.0:1 Carbs 3
6C2500 SS Corsa CV [email protected] CR 8.0:1 Carbs 3
and slightly anomalous:
6C2500 Coloniale CV [email protected] CR 7.0:1 Carbs 1 (con correttore di quota) - maybe a better carb?
Does anyone know of further changes? Pistons and carb variations would seem to account for the quoted power differences again excepting the Corsa. These probably had different cams but according to Fusi kept the same valve sizes as all the other types.

I have engine no S923911 which fits into Fusi's range of engines grouped together as Sport or Super Sport. I am interested to note that in John's list (see his post in the Ala Spessa thread) some engines prefixed by S rather than SS were fitted in cars with the SS conversion. I would like to know if mine was one of them and it has occurred to me that I can check the CR when I get the engine back from the machine shop. I obtained it dismantled and it came with a single piston (maybe not original to the engine?). This is marked 'R7-6,75. 12/45 G 275'.
12/45 could be piston manufacture date I suppose, although the engine is listed as 1940 by Fusi.
Of course if it wasn't original to the engine this won't prove anything either...
 

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I think the horsepower figures quoted are for post-war cars. The pre-war cars may have had less horsepower model for model. If I remember correctly, didn't the pre-war 6c2500 engines still have babbit (poured) main bearings (meaning less revs available; and therefore less horsepower)?
 

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Discussion Starter #5
I think the horsepower figures quoted are for post-war cars. The pre-war cars may have had less horsepower model for model. If I remember correctly, didn't the pre-war 6c2500 engines still have babbit (poured) main bearings (meaning less revs available; and therefore less horsepower)?
Fusi puts dates against them as follows:
Turismo 5 seat 1939-43 & 6-7 seat 1939-50: [email protected]
Sport 1939-52: [email protected] 1939-46 7.5:1, 90CV 1947-52 7:1
Super Sport 1939-51 [email protected]
Corsa 1939-40 [email protected]
Colonial 1939-42 [email protected]
Freccia d'oro 1947-52 [email protected]
 
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