Forum for competition engine enthusiasts. RIP Guy Croft 09/11/2020 - This forum will continue both as a source of information and as a memorial to Guy.
One could not suggest jetting based simply on the engine size and type.
The engine setup determines the jetting:
1. Valve size
2. Gasflowed including manifold
3. Exhaust manifold type (4-2-1 or 4-1) and lengths and diameters of pipes
4. Tail pipe bore to silencer
5. Silencer type (straight thru big bore?) and how many
6. Engine CR (compression ratio)
7. Camshaft type (make, lift - hopefully a billet/blank grind not a regrind).
And certainly the air intake has a major bearing: if you are inducting direct from the engine bay you are losing power and will need weaker jetting. If you duct the air via a sealed system and remote filter and have an airbox to seal off the carbs you will get more power, less risk of detonation and need richer jetting due to the higher air density.
Anyone who builds a competition engine and inducts direct from the (very) hot engine bay needs their head examined (their head, not the one on the engine..). Temperatures at the carbs can be 80 deg C or more.
Hi Philippe, Great looking car.
Tuning a car requires specific tools that most people don't know how to use effectively. Required tools include a lighted magnifying scope to inspect the spark plugs, vacuum gauge, compression gauge, carb synchronizing tool, timing light, and a Weber carb tuning book.
If you have these tools then you have already spent more than the cost of a good dyno tune. It is up to you to decide if you want to be a driver or a mechanic. Some of us want to be both.
I don't know how much experience you have with tuning engines but finding a professional to tune your car might be the less expensive way to go.
Tim
My experience is based on historical races but with Alfa Romeo Giulia 1600 and 2000 ( you can have a look on my website if you are curious :))
It's because I have no reference on Fiat engine, I search primary informations
I have suffisant tools to improve and to work on my cars.To start improvements, I like to share informations between Fiat users.
A modification will be done on my exhaust in order to fit a lambda.
Few informations:
Exhaust 4-2-1 inside diameter 42 mm
I have not diameter of the pipes at the moment (Alquati manifold)
Adm valve: 40 mm
Exh valve: 35 mm
compr. ratio: 10.6
Silencer Ø 50 mm
Camshaft Catcams 1900203
299 / 299°
258 / 258°
10.45 / 10.45
I repeat my question is only to begin with a base of settings.
Of course, I will improve by testing
The main jet controls the fuelling thru the entire range under load from 1/8 throttle (approx) to full power, the air corrector just adjusts the top end (upper 2000 rpm). Make sure the fuel pressure does not exceed about 4psi at the carbs.