room for improvement there usually when
you're looking at a carburetor sizing
like this the more manifold vacuum that
you've got at wide open throttle the
more the carburetor tends to be under
sized right it's representing the
restriction exactly if there's no
carburetor at all it would be zero
pressure drop across the plenum right so
our first data point is gonna be
manifold vacuum at peak with a 650 CFM
carburetor was 1.8 inches of mercury and
then CFM through that special carburetor
hat fixture on the dyno claims 600 at
peak well and it's indicating that there
is some restriction air so this is gonna
be kind of fun to see where it goes and
then the next thing that we wanted to
know is power there we go so nice curve
that is pretty good for this little
thing I think that's the best torque
it's made you know what I like is how
flat this is in here you know sometimes
we'll see that drop this thing really
maintains the torque down low here I
mean that's all over 400 pound-feet yeah
and that's pulling it all the way down
to 2500 rpm yeah that torques often just
horrible down 2500 that would make this
thing a great driver yeah it's the
ultimate average three to three it's
actually a really good 383 yeah it is so
let's recap the data that we just saw
with that 650 CFM carb intake manifold
vacuum at wide-open 1.8 inches of
mercury 600 CFM at peak air flow through
the car Pat it made 479 pound feet of
torque and 470 horsepower so I'm happy
me too
yeah those sorted right baseline great
engine I'll be happier when we just a
bigger carburetor on okay great well
Steven I'll sit in here and like have a
beer while you're handling nice you guys
how fast can dulcet change this
carburetor aren't you guys gonna come
out and help no we're changing the
carburetor we're telling you okay I
better go help this last
[Music]
how long is going to take us to change
carburetors hiris Eva
less than five minutes of fuel per week
that's their move this oh wow what do
you think we've made a plastic no but
it's got a nice tone to it it's not the
Liberty Bell Steve it's an air half got
it we clear
yep
[Music]
let me snug this real quick I don't like
to leave anything loose that I've
started that's a good way to make a
mistake diva's if you're halfway through
a job
don't walk away with your own this is
the air hat we were talking about
earlier there's actually a fan blade in
there basically there's a sensor that's
connected to that fan and as it spins
it's actually measuring airflow so we
get to see the airflow through the
carburetor or through the engine
the thing is carburetors are rated in
CFM cubic feet per minute of air flow
and that's what we measure right here
but how much CFM you're pulling through
just depends on how much pressure there
is pulling the air through it and that
has to do with engine size and
volumetric efficiency they have to have
a standard four rating so the standard
is one and a half inches of mercury
right but is that what the carburetor is
gonna see on the running engine no not
necessarily but again the engine is
nothing more than an air pump it's only
going to pump so much no matter what
size carburetors on it right you could
put the most gigantic 1,250 CFM
carburetor and that's not gonna show
that air into the engine by itself so
the idea here is to find the right size
carburetor the one that runs drives and
makes good power and you're like a
carburetor boffin bro yeah chest bump -
no I got to draw a line somewhere our
next test is gonna be the 750 CFM
carburetor and this is the one that if
somebody told me what engine combo this
was I'd go yeah just go to 750 on it
yeah 750 it's probably gonna be the best
one wait a minute what I thought you
said that 950 was gonna be the best one
well it's just going to work so nicely
okay yeah why I get the feeling in that
it's a bedtime story it's not like the
porridge is too hot it's not too cold
it's just yeah it's just right it's the
baby bear or whatever the porridge I
can't remember the story he's Goldilocks
and the three bears if the Goldilocks no
three Hollies yeah it will be the
Goldilocks carburetor so once again
Steve's got this thing all tuned up and
we've got it warmed up we got some heat
in the oil so we should be able to make
a whack here and look at our data
Wow I don't think this thing's ever made
that power yeah this is