Evaporating Fuel in Carter 4-Barrel Carb?

-
robodhran

robodhran

Well-Known Member
Joined
Dec 24, 2014
Messages
123
Reaction score
133
Location
Wettingen
Hi

I face the following issue on my 4-barrel carb 4120s on my 1966 Barracuda (4-speed manual):

Leaving the car standing for several days, I always have to turn the starter for a long time until there is enough gas to fire the engine. I do have enough fuel coming into the carb at first pedal already. Once started it runs perfectly.

Question: Is there a possibility, that these carter carbs have a small hole or channel somewhere, that favors evaporating the fuel in the float chamber?

I am soon going to switch the carb for the right no. 4119s

Thanks, Robert
 
I would try a 0.5" phenolic spacer between the carb and manifold. I really cuts the heat transfer down and prevents percolation of fuel in the bowls.
 
The newer fuels evaporate really quick, and especially after a hot engine shutdown.
This is one of the reasons some of us run electric pumps.
I added the phenolic spacer on my car and it made almost no notable difference on evaporation, though it did help a little with the fuel in the carb being hot.
The rotary vane electric with a return helped a TON, but that doesn't do a thing for evaporation but just gets fuel there right away on startup, and eliminates vapor locking.

Oh, and don't fall for the "Siphoning back out" theory, as it's just not possible for the fuel to get sucked back out of the carb once it's in the bowls.
 
Last edited:
I have exactly the same issue in my Valiant and Barracuda. Carter 1 bbl and Carter 625 AFB respectively. I understand today's gas formulation makes it evaporate quicker than before. Seems to me 24 hrs is the limit. If I drive either car on consecutive days, it's not really a problem. I don't mind the extra cranking because maybe the oil starts moving and gets where it needs to be before it fires.
 
KosmicKuda said:
I have exactly the same issue in my Valiant and Barracuda. Carter 1 bbl and Carter 625 AFB respectively. I understand today's gas formulation makes it evaporate quicker than before. Seems to me 24 hrs is the limit. If I drive either car on consecutive days, it's not really a problem. I don't mind the extra cranking because maybe the oil starts moving and gets where it needs to be before it fires.
Click to expand...

I wonder about that sometimes, because my motor fires right off as soon as I turn the key.
Probably a little better for the motor if oil gets there before it fires up, but if it worried me that much I would either get an oil accumulator or just a switch to kill the ignition till pressure came up.

Then again, they pretty much all fire right up without pressure first. :D
It just relies on residual oil from last time it was running until it does.
 
I know with both of my Holleys the longer they sit the longer it takes to get them started. Like Trailbeast said a prime pump helps a lot.....or EFI.
 
In my experience, Carters/Edelbrocks seem to suffer from this more than Holleys... Not that that makes me a Holley fan, by any means.....
 
Due to our great politicians trying to stuff their pockets with money they require the use of ethanol in our gas, refiners use the ethanol for octane, carbs have vents and the ethanol evaporates out quit quickly leaving gas with no octane, you have to crank new gas in carb with octane to start, if you don't use a lot of gas you can add royal purple octane boost and your troubles will disappear
 
the eddy/carter accelerator pump is located above the bottom of the fuel bowl...the bowl could still have gas in it but the pump is dry....hence car will not start ....

holley accelerator pump is fed at the bottom of the fuel bowl..it will provide a squirt of gas until the bowl is dry.....so the holley will last longer....

but as said...the gas today is lousy for a carb...

we use e85 for racing....on another web site people state that the gas will evaporate faster then the ethanol and raise the ethanol percentage...I have tested E85 that has sat for 6 month with an open vent in the plastic jug....the percentage was still at 85%.....
 
About 1973, the factory put in a thicker carb spacer, plus they reworked the fuel line repositioning the fuel filter to vertical behind the alternator. The filter stays completely full of fuel and cooler. I did both to my 67. Solved all the fuel delivery issues. Even after it has sat covered for a couple months, I turn it for 5 seconds, then 1 pedal to the floor to set the choke. Turn another 3 to 5 seconds and verooom :)
 
I had to do a couple things to stop fuel from boiling/evaporating in my carb. Starting has gone much easier.
First I had to block the heat crossover in the intake.
Second is I added the CoolCarb spacer and heat shield
www.coolcarb.com
 
gas today is designed for the new fuel injection and elec. fuel pumps that is what most cars to day have it has a lower evaporation temp it is problem for our older cars with carbs if we do not run them on a daily bases that why I put an EFI system on my DEMON and that ended the problem
 
Right next to the caps that hold the barrel, spring and step up rods there is an opening where you can use an oil can to pump gas in on both sides of the carb. Hence Prime the carb first
 
Area to area and season to season gas composition will change. Gas will evaporate, agitation, heat, and other methods will accelerate the rate. Typically what is left behind when massive evaporation is induced is a low octane liquid (we got it to 78, Lab verified) and some chemicals. When you break down what makes gasoline you'll find there are components that "light off" fast/easier than others through the process. Gasoline composition these days are designed for evaporative emissions and exhaust emissions.

The issue with Ethanol is it draws moisture, absorbs more heat and it stoichiometry ratio is higher than gasoline, meaning you need to run a higher air to fuel ratio than gasoline to get the same pop. That's why you see flex fuel vehicles have worse economy on E85 than Gasoline. The second issue is all pump sell "up too X%" of Ethanol, meaning you might get 85, or 70.
 
I have had the same hard starting issue with my 1966 Barracuda with the 273 HP engine and Carter AFB carb. If it sits for 4 days I need to prime the engine to get it to start. I just replaced the fuel pump again because of a small seep after shut down. I have not taken it for a drive yet to see if it will help. I could run the starter for a very long time and no gas before the new fuel pump --Hope the new one will help with that. The accelerator pump above the bottom of the bowel maybe another issue because there is no fuel when it sits for the 4 days. It does start right up when you prime it.
 
All of what I read above helps but the only thing we can't control is the fuel nowdays. That's the root of the problem.. A inline electric pump with a momentary push button switch can solve your problem.
 
Just a ironic note.. A few months after I fought and conquered all of the issues related to todays grocery store fuels, I found where the real 92 octane gasoline is sold. Since that day, I go that distance and pay that price. Curb idle rpm went up a little but I refuse to change a thing. It'll run on either or, so I could leave town and fill up anywhere ( short of E85. I haven't tried that ).
 
I am able to get 92 octane with out ethanol here in Minnesota and is available at many stations. I still have the carb problems when I run the 92 octane only.
 
retractable said:
I am able to get 92 octane with out ethanol here in Minnesota and is available at many stations. I still have the carb problems when I run the 92 octane only.
Click to expand...
OK, Mines a 67 273 2brl. I had a see through filter at OEM horizontal location, atop the intake. Always a air bubble in there, plus after the engine was hot I could watch the filter fill and empty repeatedly. That's why the idle wasn't consistent too. It took me a little while to finger out that empty wasn't empty. What I was seeing was fuel vapor flowing backward from the carb bowl. Confirmed the bowl vent was open. How the heck there could be more vapor pressure than would escape through that vent is still a mystery. Anyway...
The thicker base gasket and relocating the filter ( changed it to a metal type also ) cured it.
I did need to alter the choke rod height to compensate for the changed carb height .
 
Here is another idea to try, I had a holley 600 carb that did the same thing. To finally solve the problem I removed the carb filled it with fuel and set it up on the bench to see what was happening. Turns out I had a slight leak that was dripping into the venturi area. It was a while ago but i think i replaced the base gasket or the throttle plate assembly was warped. but cured my problem for sure. I think with the carter type carbs are less likely to have that problem but you never know.
 
65Val said:
In my experience, Carters/Edelbrocks seem to suffer from this more than Holleys... Not that that makes me a Holley fan, by any means.....
Click to expand...

Yep, and it's the design of the bowls that make the difference.
Holley bowls hang out in open air and the Carters and Eddies are totally enclosed in the body of the carbs.
 
toolmanmike said:
All of what I read above helps but the only thing we can't control is the fuel nowdays. That's the root of the problem.. A inline electric pump with a momentary push button switch can solve your problem.
Click to expand...

I wonder what would be the best spot to place the pump. Is there a specific brand/type you would recommend?

Robert
WP_20161030_12_01_01_Pro.jpg
 
You must log in or register to reply here.
-

Back
Top