[Tom Vaught]

When you put the Holley carb in a box you also give the incoming air an equal chance with feeding each Booster the same amount of air.

When you install a Bonnet on the Carb you now can drastically change where the airflow is going to the Boosters.

I am going to post up pictures of 4 different bonnet styles and then discuss each one a bit.

The first Picture of of a CSU Bonnet. Basically the bonnet inlet is aligned with the centerline of the crankshaft, the air enters the bonnet and smashes off the back wall of the bonnet and enters the carb boosters. The rear boosters get a bit more air vs the front ones but you can jet for that air "in-balance" under boost conditions.

Picture #2 is of a old style Extreme Bonnet with a Divider Wall horizontal in the flow path.
The idea here is to split the air flow into a upper air path and a lower air path and have the boosters all
get about the same airflow. Problem is if you can't mount it on the centerline of the crankshaft and have
to put the inlet facing the passenger fender than the split is left bank/right bank (not front or rear separation)
More difficult tuning for sure.

Picture #3 is our HO Racing Bonnet again. The air basically expands outward after the exit from the feed pipe and slows
down quickly and expands over the whole carb top. There might be a slight bias due to the inlet not being exactly on the centerline of the crank but not a big deal. The Bonnet also has a air flow vane in the roof of the bonnet to help direct air
to the Q-Jet Carb properly.

Picture #4 is a Procharger Bonnet and is low profile and the inlet faced slightly downward from the carb airhorn.
A nice piece if you have limited hood clearance and you can locate the inlet on the centerline of the crank and get
even flow to the carb boosters.

Most of these bonnets (except for the HO Racing unit can be pointed other places but the engine needs to be tuned
for that booster Air in-balance.

Equal Air Distribution is everything on a boosted bonnet set-up.

Tom V.