Carb for 402
Thread Starter
Instructor
Joined: Mar 2009
Posts: 246
Likes: 0
From: Cameron Tx
Carb for 402
it had a proform 750 racing and I feel i sould p[ut the same back on it as performance seemed good. My question is what is the difference between the street series and racing series to justify the $100
thanks
thanks
Race Director
Joined: Apr 2000
Posts: 17,676
Likes: 201
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
A racing carb usually has no choke or choke tower and usually is more tuneable ( ie screw in air bleeds etc ) A true race carb will not have any vacuum ports either for brakes PCV vacuum advance etc. 
Burning Brakes
Joined: Dec 2003
Posts: 1,004
Likes: 7
From: Adelaide South Australia
street carby....
It has a choke assembly for easy cold weather starting... this does cause some flow restriction at higher rpm.
Also has vacuum ports for PCV valve, and vacuum accessories... You know, things like power brakes, popup headlights and wiper door, air-conditioning control valves etc...
vacuum port is also used to provide vacuum advance for the distributor timing... assists in better cruising fuel economy, and better/smoother power on the street, where partial throttle situations are used.
racing carby...
NO Choke, but has contoured shape venturi's to improve air flow at max rpm (flow velocity)... They do provide more tuning flexibility for extracting maximum power in custom modified engines... adjustable air bleeds allow very good fuel control, as well as 4 corner idle jets and other goodies such as annular boosters on some models...
Everything is designed to provide maximum performance.
No vacuum ports, so if you want vacuum, you need to source it from the manifold.....
Then there's something in between....
4150 HP Street series
Has most of the performance benefits of racing carb, whilst still providing some good design aspects for street use.
I have one of these, but if you drive your vette in winter... you'll need a choke.
**************************************** ******************************
added:
forgot to mention..... most street carbs have vacuum operated secondaries... provides a smoother transition to the secondary throttle ports as throttle is opened. Considerred to be better on automatic trans vehicles, and also provides better fuel economy.
Racing carbs tend to run mechanical actuated secondaries... when the foot goes down, all 4 barrels open immediately. Jetting and overall tuning needs to be very good to minimise coughs/splutters, and they tend to drink more fuel. They do provide better performance when set up right.
It has a choke assembly for easy cold weather starting... this does cause some flow restriction at higher rpm.
Also has vacuum ports for PCV valve, and vacuum accessories... You know, things like power brakes, popup headlights and wiper door, air-conditioning control valves etc...
vacuum port is also used to provide vacuum advance for the distributor timing... assists in better cruising fuel economy, and better/smoother power on the street, where partial throttle situations are used.
racing carby...
NO Choke, but has contoured shape venturi's to improve air flow at max rpm (flow velocity)... They do provide more tuning flexibility for extracting maximum power in custom modified engines... adjustable air bleeds allow very good fuel control, as well as 4 corner idle jets and other goodies such as annular boosters on some models...
Everything is designed to provide maximum performance.
No vacuum ports, so if you want vacuum, you need to source it from the manifold.....
Then there's something in between....
4150 HP Street series
Has most of the performance benefits of racing carb, whilst still providing some good design aspects for street use.
I have one of these, but if you drive your vette in winter... you'll need a choke.
**************************************** ******************************
added:
forgot to mention..... most street carbs have vacuum operated secondaries... provides a smoother transition to the secondary throttle ports as throttle is opened. Considerred to be better on automatic trans vehicles, and also provides better fuel economy.
Racing carbs tend to run mechanical actuated secondaries... when the foot goes down, all 4 barrels open immediately. Jetting and overall tuning needs to be very good to minimise coughs/splutters, and they tend to drink more fuel. They do provide better performance when set up right.
Last edited by OzzyTom; Mar 6, 2009 at 12:12 AM.
