Technical Mopar long ram intake and carburetor questions

I think there's actually two driveability issues at hand here, though it's easy to understand how they both get rolled into one.

The carb icing results from the high velocity air flow thru the venturis and the atomization of fuel which results in a temperature drop in the throttle bores. It also depends on the presence of humidity in the air passing thru the carb. Icing can and does occur at relatively high ambient air temperatures if enough humidity is also present.

A different, separate driveability issue can occur when the intake manifold and its runners are cold. A well atomized fuel and air mixture produces the most complete combustion. But when the air/fuel mix enters a cold intake manifold the atomized fuel will attempt to drop out of suspension and condense into larger fuel droplets that don't ignite as easily or completely. And combustion efficiency and power output suffers as a result. This is mainly a problem at lower engine speeds when the velocity of the air/flow mixture thru the manifold is slower.

 

@Rickybop,
Another cool thing about the Mopar drag cars from the early 60s is that most had 'nest of snakes' headers. I hope you can incorporate that look on your '53.

An added benefit would be that you could put a removable stove on one of the header tubes and heat the intake. (both the incoming air and the base of the intake under the carb)

Can you get it installed before Autorama? If you being it, I'll by you a coney!

 

Have it together for Autorama?
Um... no. LOL
I want a Coney anyway.

Pipes? Heck yeah. Pipes.

 

Why couldn't you mount small electric coil heater elements to the bottom of the carb wells to heat things up until the engine is up to temperature? A switch on the dash to turn it on and you flip it back off when you get running.

I SO want to buy the cross ram on FB Marketplace for the 413 in my '55 Ford, but the guy won't ship it.

 

@nitrobrother,
Where is it located? Maybe a fellow HAMBer would pick it up and ship it to you.

 

I think you guys may be overthinking the warming up the Carburetors, though I'm sure it would help. On my friend's hot rod with no heat up and just hanging in the air It was driven year round with no problems , though it did have The Holleys if that would make a difference. It had manual chokes and he would manually turn one on so that both of them had a high idle and probably let it sit a minute and then shut them off. Get in the car and go.

 

Roanoke VA.

 

Pretty big differences between the "cold" in CA (for most of the state anyway) and the "cold" in Michigan. Also a pretty big difference between a daily driver and a weekend cruiser.

In the mid west, a winter day could have 60 degrees at lunch time, but have 0 degrees and blowing snow for the drive home at 5 pm.

 

Buncha Hot Hands stuck to the air cleaners maybe?

I used to drive a rumpity old Chevy short bed stepside. 350 4spd posi Holley headers.
No hood.
No air cleaner.
No choke.
Spring, summer, fall, winter.
Sometimes 6" of snow on the engine.
No big deal.
Most I ever had to do a couple of times was maybe brush off some of the snow and pour a little hot water around the carburetor.

I don't think a finicky long-ram is gonna bother me too much.


It's still good to have the conversation about how to deal with it.

 

It'll add to the fun.
A little extra warm up time.
More stuff on the dash...
Couple of extra temperature gauges maybe...
Two choke knobs instead of one...

 

Thanks very much, everybody... for sharing what you know.
And for the good links, too... so I can learn even more and do a good job.

 

Pics of a 2903S I have showing the bores.

 

Thank, @mineseats9

The primaries and the secondaries are definitely not always exactly the same size on the AFB carburetors. But they're considered to be square bore.
@carbking suggested that maybe they should be called "almost square bore".

Having the original carburetors isn't as critical as I feared. There are other models we can make work. And in fact, I found out that there's at least one minor shortcoming with the original AFB 2903S carburetors. Apparently, the idle adjustment screw is actually an air bleed needle valve located in a spot that's difficult to reach. But that port can easily be closed off and a standard type idle adjustment screw added to the more common location, contacting the actual throttle.

 

[QUOTE="Rickybop, post: 15069783, member: 56729"

The primaries and the secondaries are definitely not always exactly the same size on the AFB carburetors. But they're considered to be square bore.
@carbking suggested that maybe they should be called "Almost Square Bore".
[/QUOTE]

Sounds like a good excuse here to initiate some new official terminology.

Introducing: The new Carter ASB Series carburetor!

As if things aren't complicated enough already . . .

 

@ClayMart
Your avatar looks ASB-able.

 

Anti Social Behavior?

Might give you a good ass-kickin'! She keeps her left leg in shape doing tire changes on monster trucks.

 

The majority of factory AFBs have a .25 inch difference between the primary and secondary throttle plates (1.44 vs. 1.69). A lot of the late '50s/early '60s Mopar AFBs had the same size front and rear.

 

No no no...
I was complimenting the young lady. Using our carburetor terminology.
"Almost Square Bore"... able.
You know... cuddly.

 

Saw this ad on FB Marketplace, I'll delete if it's not ok to post?

https://www.facebook.com/marketplac...wse_serp:15763244-e734-4454-89bc-3729080f046c

 

Guess that was just me over-thinking things again. Typical . . .

 

S'alright, Queekdraw!

 

When we did the 'Bounty Hunters' clone I had the original Carters that Tom Sneeden removed and replaced with Holleys per Mopar specs. I took them to AED and tested them on their airflow bench, at high RPM/AirFlow the fuel would form a little inverse fountain an inch or so above the carburetors, as the molecules bumped into each other they'd form a droplet too heavy to sustain in this cloud, it'd go into the engine to make that high speed stumble that drove the original Superstockers nuts, thats was why Mopar switched to the Holley on the MaxWedge, maybe mid-64? anyway that solved the problem.
Maybe Jon knows more about this?
I just know from the testing and what Tom told me, but its funny how stories and memories can change over 50-60 years.

 

Interesting, @oj

 

I seem to remember a hot rod magazine maybe that the cover picture was a cross ram carbureted engine on a dyno running and it had the fuel dancing above the carburetors. A big balance tube would help this problem.

 

I'm curious, @oj
You said the Carter carburetors were tested at high RPM/Airflow.
I wonder at what level CFM the condition appears. RPM equivalent?
Can we be confident it was above 5,000 RPM?

 

It depends on your engine size, I'd say the cloud was forming at 300ish cfm, I was told that Mopar was aware of this condition and that they developed air cleaners with a tallish neck and that mitigated the cloud. Except that the very first thing a drag racer gets rid of is the stock air cleaner. It made no sense to me at all and I felt that I never did hear the real story behind it.

 

Thanks, @oj
If I'm cipherin' correctly, 300 CFM would be pretty low RPM.

440ci x 2600rpm x 3456 / 90%VE
Would get you about 300 CFM.
That's right about where the long ram intake is supposed to excel.

More research for me to do.
And some experiments later.

 

I have a set but would love to find the exhaust manifolds to go with them. If a can’t find a set I may go with twin sniper efi on them

 

What motor are you putting the intake on?

 

440