Chokes and jetting for 2Ltr Fiat TC on 45DCOE's

[Fiat CC]

I have started to build a mild 2litre twin cam for my Fiat 124 coupe, with specs as follows:
* Regatta 100s pistons
* Brand new Fiat 132 2 litre block
* Regatta 100s head match ported to inlet manifold
* Cams with following specs:
Advance Ground on Cam: Lobe separation: 108
.050 VALVE TIMING
Inlet opens: 16 BTDC Closes: 52 ABDC .050 Duration: 248
Exhaust Opens: 52 BBDC Closes: 16 ATDC .050 Duration: 248
ADVERTISED VALVE TIMING
Inlet opens: 34 BTDC Closes: 70 ABDC ADV Duration: 285
Exhaust Opens: 70 BBDC Closes: 34 ATDC ADV Duration: 285
Inlet lobe lift at TDC on the over lap:

Valve lift Inlet: .4431 Inlet Rocker Ratio: 1.00
Valve lift Exhaust: .4431 Exhaust Rocker Ratio: 1.00
Valve Lash Inlet:.005 Valve Lash Exhaust: .007
* 4-1 Exhaust
* Twin 45DCOE carbs
I will post photos as soon as I get hold of a digital camera.

Anyway, I am after some ideas for choke and jet starting points. I have a mechanic who has a reasonable amount of Weber jets to play with...
Thanks,
Reuben

[Guy Croft]

I must know the maker of the cams, and whether they are billet or regrind. Cam data per-se means nothing to me. If you don't know I can't help.

GC

[Fiat CC]

Hi Guy.
The cams are made by Crow Cams, and they are billets not regrinds. I am running a pair of these cams, not just inlet. This is their #307 grind I believe.
Thanks,
Reuben

[Guy Croft]

OK:

38 ch
F16 emul
145 main
185 a/c
50 or 55 F9 idle
45 pump


Hope that helps,

GC

[Fiat CC]

Great, much appreciated Guy! You are a champion!!!
Reuben

[Guy Croft]

Always nice to have my advice acknowledged, Reuben, thanks.

Also worth reading the adjacent thread concerning headers etc:

http://guy-croft.com/viewtopic.php?t=1011


GC

[Fiat CC]

Thanks Guy. Another useful and informative thread there. It's inspired me to replace the rather simple 4-1 manifold with something following those specs. How easy would it be to make up a manifold with those header lengths and make it fit in a RHD 124 coupe? I know it is quite tight in there, even with the setup I am currently running. What sort of gain can headers like these offer?
Thanks as always,
Reuben