Race Engine Forum UK

Hello Guy,

I just finished my very ambitious 1608 BC racer head project. The case is as such:

44IDFs
Abarth 068 cams
Waffle manifold opened to 45 inlet and 35 horizontal and vertical outlet.
Head with 43.5in valve with 36 inlet port and 35 venturi, deshrouded combustion chamber around bigger valve. 36out valve with 34 parallel outlet port.
4-2-1 manifold single silencer.

What do you suggest on initial jetting? I am thinking of:
idle 55
emulsion F9
main 150
air 180

Please advice. Thanks in advance once again,
Vassilis.

I am sorry for not replying sooner, been pretty 'tied up' at work.


You wrote:
1608 8V TC Fiat with Weber 44IDFs, Abarth 068 cams OE Fiat 'waffle' manifold opened to 45 inlet and 35 horizontal and vertical outlet, head with 43.5in valve with 36 inlet port and 35 venturi, deshrouded combustion chamber around bigger valve. 36 ex valve with 34 parallel ex port; 4-2-1 manifold single silencer.

You asked if this jetting was right:
idle 55
emulsion F9
main 150
air 180


For a start - in case you did not refer to it above - I would be on 36mm chokes (secondary venturi). 34mm chokes will do but 36 will definitely give more top-end power.
Idle jet for the 1608, I suggest 55 is too big and 45 would be OK.
I would use the F11 emulsion tube, I don't think you'll need the richer F9 on that small engine.
The main jet again is too big for those small cylinders, I reckon 140 will be big enough.
The air corrector is probably too small and thus too rich at the top end, I think 185 or bigger (say 190 or even 200) will do.

That, I think, is a good starting point.

Once again, sorry for taking so long to answer this important thread.

GC