Carb recommendation

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MZimmerman

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Hello, Trying to pick a new carb for my 360 build. The Carter AVS is leaving me stranded all the time when I let the motor sit 20 minutes. It is a new rebuild out of a Lil' Red Express truck. Certainly makes my 71 Valiant fly. I have a spread bore intake on it off of a 340. So I need to stick with the spread bore. Any help is greatly appreciated. The car is not necessarily for the strip but it is no Sunday driver either.
 
Well, no. I was told by the guys around here that those carbs have a problem with the gas boiling out since the bowls are on the bottom. I do have a thermo adapter that seems to help a little but the car definitely seems like it is flooded from the gas boiling into the intake every time it is shut off for more than 5-10 minutes. I have been told my several people that the carb I have will work fine but I will end up having to get a new one. Really looking for a new carb recommendation.
 
Any model number on that Holley?
Love a 4779 double pumper if it’s got a good converter and gear.
The 3310 is a great vacuum secondary version, for milder applications.
Both start nice, idle great, and will get the most out of a small block.
 
Love a 4779 double pumper if it’s got a good converter and gear.
The 3310 is a great vacuum secondary version, for milder applications.
Both start nice, idle great, and will get the most out of a small block.
I love the 4779 also, but he wants a spreadbore….
 
I love the 4779 also, but he wants a spreadbore….
It wouldn’t Bother me to run a Holley square flange on a spread bore intake. Did it on a Strip Dominator for years ran great.
You could always run a spacer which most engines react well to.
 
Hello, Trying to pick a new carb for my 360 build. The Carter AVS is leaving me stranded all the time when I let the motor sit 20 minutes. It is a new rebuild out of a Lil' Red Express truck. Certainly makes my 71 Valiant fly. I have a spread bore intake on it off of a 340. So I need to stick with the spread bore. Any help is greatly appreciated. The car is not necessarily for the strip but it is no Sunday driver either.
I’ve got a 74 360 Thermo-Quad if you’re looking for one. PM me if interested.
Jake
 
Carter AVS Carburetor H8 4611S. Thats the tag, and it is a spread bore??? Would like a modern replacement for that carb.
 
So let's get some things clear.

You have an AVS on a ThermoQuad intake? Is this correct?

You have an adapter to run said square bore carb on a spread bore intake?

That's almost always a bad thing, and I've done enough testing to know that a spacer isn't always a good thing. In fact, most of the time it's a loser.

The number ONE issue with the problem you have is easily corrected.

You need to pull the intake, and buy a gasket that blocks the exhaust crossover that goes from one head to the other right under the intake manifold.

There is no reason to leave all that heat going across there. Unless you think you need a choke. I haven't used a choke since 1982. Of course, you could still use an electric choke if you feel the need for it.

That said, you can't run all that heat under the carb like that and expect any carb to be happy about it.

Block the heat crossover and it will help everything.
 
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This is the 4611s I have. Isn't this a spread bore? Also I have this on a OEM 68 340 Cast Iron Intake, Bores match. The plate (adapter) i have is just a heat sync plate, not spread to square.
 
View attachment 1715412331This is the 4611s I have. Isn't this a spread bore? Also I have this on a OEM 68 340 Cast Iron Intake, Bores match. The plate (adapter) i have is just a heat sync plate, not spread to square.
technically, the bores are spread. It's called and referred to as a square bore, like the edelbrock carbs. '68 340 intake is a square bore - 4 hole.
 
Ok. Thanks, Learned something new :) Always considered smaller primaries being a spread bore. So, now that we have that straight. Recommendation??? I will check on the cross over gasket, not sure which set I put in when I rebuilt it. Either way, still looking for a new carb.
 
Ok. Thanks, Learned something new :) Always considered smaller primaries being a spread bore. So, now that we have that straight. Recommendation??? I will check on the cross over gasket, not sure which set I put in when I rebuilt it. Either way, still looking for a new carb.
4779 Holley 750 double pumper is what I'd run on it.
 
Ok. Thanks, Learned something new :) Always considered smaller primaries being a spread bore. So, now that we have that straight. Recommendation??? I will check on the cross over gasket, not sure which set I put in when I rebuilt it. Either way, still looking for a new carb.
When you mentioned you had an Avs told me enough that it’s the same as a Holley flange.
A Holley will bolt up with a minimal of fuss.
 
No! That is the square ore carb even though your measuring a bigger secondary side. It is the big offset for a spreadbore.

It also doesn’t need an adapter on the ‘68-340 intake unless the butterfly’s won’t open fully. Or your also missing the thick gasket.

If your carb is boiling off fuel after a few minutes you have a serious issue and start with YellowRoses heat block off plates between the head and intake.

Secondly, use the OE type THICK gasket. They are about.333 thick, give or take. There that thick stock because of the problem your having.

Next is to double check float levels, lean/rich conditions.
And sorry Holley lovers, even the fuel bowls can have fuel boiled away on the Holley’s. That’s also why the aftermarket sells heat shields for them.

View attachment 1715412331This is the 4611s I have. Isn't this a spread bore? Also I have this on a OEM 68 340 Cast Iron Intake, Bores match. The plate (adapter) i have is just a heat sync plate, not spread to square.
 
So let's get some things clear.

You have an AVS on a ThermoQuad intake? Is this correct?

You have an adapter to run said square bore carb on a spread bore intake?

That's almost always a bad thing, and I've done enough testing to know that a spacer isn't always a good thing. In fact, most of the time it's a loser.

The number ONE issue with the problem you have is easily corrected.

You need to pull the intake, and buy a gasket that blocks the exhaust crossover that goes from one head to the other right under the intake manifold.

There is no reason to leave all that heat going across there. Unless you think you need a choke. I haven't used a choke since 1982. Of course, you could still use an electric choke if you feel the need for it.

That said, you can't run all that heat under the carb like that and expect any carb to be happy about it.

Block the heat crossover and it will help everything.
I even gave you a like today... it should now be obvious to everyone I'm at home and very sick with a cold...
 
It's not the carb, the issues is today's fuel. As stated you need an insulator, and possibly an electric pump to prime the bowls or an electric pump with a regulator and return line to your tank. I'd replace the carb only if its holding your combo back or has other drive-ability issues that a rebuild won't fix.
 
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