Dear friends, my weber engine needs more power.
I have a standart 351c block
with a flat tappet cam with about .06 lift
on a ported closed 4v heads.
Heads use crane roller rockers .
So first of all , the mixture is much to rich.
It runs now at about 11:1 at 3500rpm @ about 100miles per hour ( le mans gear ratio)
F11 emulsion tube
and only 38 Venturis.
So my plane is to switch the venturis to 42 or 44 mm to increase top end power.
Car runs only 250 km/h Gps locked. When it is a cold day maybe 260 km/h
The engine only spin 7000rpm
from 6000 to 7000 rpm there is no more power aviable.
In this range the air to fuel ratio is about 10 :1 at full throttle.
Is there someone, wich have any experience in change the venturis ?
The 4V head have verry big intakes so i think a small ventury make no sense.
I can not understand, why we restrickt the 48 mm to 38 mm only to reach more air velocity. I guess this high air speed is only in the carbs. When the air arrives at the intake valve , it will be slow again , because of the big ports from the heads.
What is your opinion ?
Should I try to use 42 mm Venturis ?
I found a old race setup from a porsche :
it use 48 idas on 42 Venturis with a F7 tube , 165 main and 170 air correction and a 5 inlet "valve"