One of the most frequently asked
questions at our shop is how big of carburetor do I need for my
application. Some of our customers have made the decision and some need
our advice. Its surprising that with all the "flow" talk that's been
published over the years that its not the main topic at our shop over
the phone or e-mail. We get our share of guys that want us to tell them
that our BIGS Stage 5 750 will flow 965CFM or that when were done
setting their carb up it will flow 200+CFM more but were not about that.
When you read absurd flow numbers that a 750 is flowing 985CFM you can
rest assured its pure bullshit! Without enlarging the venturis or
butterfly's there is just not that much room for pick-up. Any time spent
on the dyno will show that real flow numbers are much lower. Its like
Grandpa used to say, " son, its the engines ability to EXCITE the
carburetor " We firmly believe that our customers are much better served
with clear, concise and accurate information, rather then trying to
dazzle the folks with the smoke and mirrors approach.
When we start to decide on a carb choice for our customers we ask some
basic questions that our customers can answer. Some of the large factors
are what are we going to use the vehicle for. If its a street car only
but has a hardcore race engine we have to run a completely different
carburetor then if it were a drag car with the same engine. Because on
the street, idle/part throttle/and cruise is very important. So we would
generally try and keep with a carb that might be 5-7 horsepower short at
peak but much more manageable for the street. Most of our street/strip
customers are willing to sacrifice some horsepower up top for a better
running carb down low. In an all out drag car/mud bogger/truck
puller/ application were after every horsepower we can get and down low
is out the window. But with loose convertors ,lencos and clutches down
low don't exist anyway.
For many years we were 850 freaks at our shop. The old reliable 4781 is
a great carb. One of the problems that we saw was that with a larger
cube type engine (440 for example)that is made to run below 6500 and
rely on torque, the 850 was lazy down low in a street car if we had a
3000 type stall convertor or lower. This was because of the large 1 9/16
venturi at the top of the 4781. we liked the 1 3/4 base but that 1 9/16
venturi had to go. So its either add annular boosters which cut the flow
back and improve the bottom end or we did allot of the body swaps. Take
a 750 body, add a 850 base and now she comes alive. With no loss on the
top end! Now that's a great combination!
We now have the 950 to work with and its truly a great carb that's been
a long time in the making. Our BIGS Stage 5 950 comes in several
different venturi sizes depending on what we feel your engine will
handle. Still staying as close as we can to the 750/850 combo we spoke
above above but just tweaking it some more. Some applications need more
flowing capabilities then the 750 type venturi will allow so we do
enlarge the venturi at the top depending on the specs. These carbs make
for excellent bottom end response. 60' times and stop light to stop
light cant beat!
With the trend seeming to be going towards stroker motors, Horsepower
and Torque levels are up from where they were 10 years ago. The cylinder
heads, intakes, cams, ect. have came along and made building power allot
of fun. Its cool to here some of our customers building their very first
engine with parts that the older generation would have killed for or
never thought would exist. But that's progress, and where its going to
go from here will be fun to see!
So if your shopping for a new carburetor and need some help determining
the correct size and not just the biggest flow numbers, drop us an
e-mail or give us a call. We can talk with you about how your going to
use the vehicle and what we feel will work the best! We have some of the
best customers and would like to extend a special thanks to all of you
that make our job FUN! Your friends at BIGS!!
