I just bought an autometer A/F ratio gauge and what I see is that I run a little bit rich most of the time but when I floor it, the higher the RPM the leanest I am.
When I reach 6000rpm, I am very lean (last red light and sometimes nothing).
I can feel that the car is stumbling a little bit.
What should I do to run richer in high rpm at WOT?
My carb is the Holley 600cfm 4160.

Thanks for your help,

Jacques.

 

What's your cars main purpose in life, street driving Mon.-Fri. strip on the weekends? If so that will be the case with your mixture. What will be the ideal set-up on the street will be lean at the track otherwise you'll be fouling plugs all the time in stop and go traffic. You might be able to fatten it up a little and still be all right just have to change the plugs a little sooner than your used to, but that's just a little easier than a short block rebuild cause you've got a hole in your piston. I got a 355 in mine with a Holley 750 VS ended up putting #76 up front cause I had the same thing happen. When I play on the street during the week, by Fri. they're black as coal, the humidity is'nt helping right now either, but by Sat. night they get cleaned out and I get the hint of tan which I like to see.

 

So you are saying that I should change my jets on the primaries (I just swapped from TBI so I don't really know a lot about carb).
If I bumped the fuel pressure a little or close the choke a little (it is open all the time right now) would it change something?

Thanks for your answers,

Jacques.

 

No you don;t need to mess with the choke or probably even the primaries.

Jet up the secondaries 2 steps at a time till it reads where you want it. If that doesn't help, then look into a better pump.

 

I think that the 4160 carbs don't have jets for the secondaries but a metring plate.
I may be wrong but if it is the case, what should I do.
BTW if it helps, I am thinking about changing my intake to a dual plane, the single that I have was because I had TBI.
Would a dual plane reduce this problem?

Jacques.

 

The single plane intake is a mistake on a street 305.
Get a dual plane. The stock jetting on a #1850 should not cause the *severe* lean condition at wot that you are seeing.
First check that your exhaust system is not leaking. It will suck in oxygen and give a false lean reading on the guage.
Barring this, your severe lean condition at WOT is probaily being caused by bad fuel flow, causing the float bowls to empty,
starving it for fuel. Could be a bad or too small pump, a restriction in the fuel line any where even in the tank.
Could be a rubber hose section is soft when hot and is being sucked shut. You 'll want to install a fuel pressure guage inline
between the pump and carb and read the fuel pressure while at WOT and high rpm. If it is less than 3 psi, you have a problem some where along the fuel line or the pump itself is bad or too small. Some cars have a sock filter in the tank that can get plugged.

At any rate your stock jetting should be 64/66 primary jetting
with a #9 or #39 secondary metering plate.
If this jetting was too lean it would not be severly lean like you discribe so I'd suspect fuel flow capacity as the culprit first
before you start jetting. When you get this sorted out you might get/buy a #21 metering plate. This is as rich as you'll ever need.
But will not correct a lean condition caused by bad fuel flow.
At WOT your A/F R guage should read full rich or close to it
at all times. 12:1 to 13.5:1 When you fuel system is sorted out, you will not need big jetting and your car will not use up plugs
or load up or surge. If you need a jet that is more than 5 jet sizes
from stock, there is something else wrong.

 

I just converted it from TBI so I still have my stock in-tank electric pump. I have the Mallory fuel pressure regulator between the pum and the carb. I never had a problem with my pump when I was using injection.
I was thinking that it may be my gauge that reads wrong at WOT because of the heat of the exhausts on the sensor. I just posted it as another topic.

I will check my fuel pressure.
Can an electric fuel pump no be enough?

Jacques.

 

Yes your intank pump may not be enough.
You'll have to determine that with a fuel pressure check @WOT

A O2 sensor needs the hot exhaust to work, but
any exhaust leaks will throw it off.

Your mallory regulator was never designed to work against such high pressure as a fuel injection pump has.
It may be so cranked down tight to control pressure
that it is restricting.

You'll have to go throught the whole thing and find the flow problem Good Luck

 

Thank You all