carburator need more performance

[TyrolMopar]

I rebuit my Holley 4150 4777-3 650cfm double pump carburator
and want that he become more performance so I want ask
how i could get more performance ?
Which Main Jet for Prim and Sec are better to become more performance ,
higher or lower size ?

[sassygreen]

We will need a little more information.  Big block? Small block? Headers? Dual exhaust? Single Exhaust? Cam? Heads? Auto? 4 Speed? Rear end ratio?

[cudabob496]

 best performance will be when your spark plugs are a nice tan color.  Not black,
and not white.  Look at the porcelein part right below the positive electrode.

https://www.youtube.com/watch?v=saCDmyiBmb0

[Chryco Psycho]

Tuning is everything , I have a basic guide in the archives you can follow

[TyrolMopar]

The carb be on a 360 engine from the year 1972 an have a Weiland 7505 intake manifold,
also a mit Comp Cam,  no name headers,  msd super conductor 8,5 mm stark plug wires, 
msd blaster 2 coil,  msd 6200 ignition box. 
That's what i know

[cudabob496]

looks like it came with 67 and 73s, so start there.
Then, if plugs look good, you will get no more performance from the carb,
even if you try a new carb.

Cheap power comes from these www.ramairbox.com.

http://www.carburetion.com/CarbNumber.asp?Number=4777-3

[TyrolMopar]

Yes the carb have 67 prim and 73 sec main jets but some people sag
to me That's i should but in 65 prim and 72 sec main jets and i don't
unterstand why.
Mm 74' barracuda have a dual exhaust,  a 3:55 rear end ratio,  a 727
autom.,  new ngk v-line spark plugs.

So the only Performance i could get from the carb is when i clean them and
change the gaskets? 

[cudabob496]

If your plugs are a good color, and the rest of the carb is tuned right, then
there is no more power available from your carb.  Higher jet numbers just
make the charge going into your cylinder heads more rich with fuel, and you will
loose power.

A well tuned engine is a good way to get maximum power. 

If you want to be quicker on the street, go to a higher stall converter in your
auto tranny. 

But to make the engine even more powerful, you would need new heads and a cam, or
you could have your heads ported.

Regarding cold air induction, you get about 1.5% increase in power for every 10 degrees
you lower carb inlet temp.  So, if you lower inlet temp by 50 degrees, thats 7.5% power,
or an increase of 30 hp on a 400 hp engine.

[cudabob496]

The carb be on a 360 engine from the year 1972 an have a Weiland 7505 intake manifold,
also a mit Comp Cam,  no name headers,  msd super conductor 8,5 mm stark plug wires, 
msd blaster 2 coil,  msd 6200 ignition box. 
That's what i know

A dual exhaust with X-pipe is a good performance addition.

[TyrolMopar]

Higher jet numbers just
make the charge going into your cylinder heads more rich with fuel, and you will
loose power.


If you want to be quicker on the street, go to a higher stall converter in your
auto tranny. 

And what is with lower main jets ? If the original main jets set are to high , lower one will be better or not ?

Will be a stall converter with 2400 better or one with 2800 or 3200 ?

I don`t know which one will be the right one for me , the ideal one for my engine with this components my 360 engine have .

sorry for my bad grammar .

[Street_Challenged73]

The jetting will be dependent on the condition of the engine (hp, designed power range from cam, heads, etc), so it doesn't necessarily mean that a smaller/bigger jet set will be one way to go. Ideally, you would want to have it tuned on a dynometer so you're able to see which jets the make the most power for the engine while still maintaining good characteristics.

As for a stall converter, I believe that shock is somewhere around 1200-1500 RPMs, so unless you intend to run it down a track I'd keep it around low-mid 2000s; 3000+ tends to be used mainly for bracket racing or people who have a very potent, higher HP engine.

[cudabob496]

an AFR meter can save a trip to the dyno

[Street_Challenged73]

^good call!

[cudabob496]

if an air fuel ratio meter is reading around 12.5 to 13.5, your jets are probably the correct ones,
and you would not want to change them.  That's what my AFR meter normally reads, so I have
my jets at 77/86 right now.  I don't bother looking at the plugs anymore. In the summer, when the air
is hotter, my AFR meter starts to stay below 13 all the time (less oxygen due to hotter air) so I have been
changing the primary jet to 76.

when I first installed the AFR meter, my AFR was around 10!  turns out my primary jet was #84,
so I quickly changed that to 76, and the car ran a lot quicker, and the exhaust did not smell
so rich and irritating.

When cruising, 13.5 is good. If you want to floor it and go fast, you want to see around 12.5, when
the secondaries kick in.

[TyrolMopar]

I thank you all alot for this infomations , helps alot.

@ cudabob496 which AFR Meter Kit are you installed ? Was the installation of this kit difficult ?
Did you self made the hole for the sensor in the exhaust or did you have a header with a connection for this ?

Do install a AFR meter are a great idea which i want know mor about it .

So the Holley carburator will get cleaned and rebuilt without change the jets in the next few days, i will
look at first what the AFR meter say befor i change the jets .

I search also for headers , so i must take a look for one with connection place for the AFR .

Is it ok when the one sensor where be in a kit is installed in one header or need 2 sensors for right and left ?