Lets talk Emulsion tubes

[priobe]

Rick,
I agree with the elevation issue. Here in FL. our land is flat and at sea level. This is something I was never able to experience. However, during my readings on carbs, for what it is worth, they say you can get away with not jetting a carb up to 5000 ft above sea level. Now I have not idea if that is true.

If anyone can add to this it would sure be helpful.

[DMXF]

Priobe - You should be able to model the etubes to establish a good matrix as to exactly what each would accomplish. It would no doubt be quite involved and should ideally include correlations to various testing, as available (this aspect may be very important). You can calculate hole areas, passage areas, correct for some holes being at an angle, etc. You may end up with something that can be used to determine the tube number direction to go, or even maybe how to modify an existing tube by drilling more holes, etc.

[priobe]

Caprimaniac,

If you are running good on your idle to 3000 I would not change the emulsion tube.

What I would change depending on where you are experiencing the 12.5 A/F.

If it is higher RPM like 4000 then I would lower the air corrector.

What is mains and aircorrector jets?

At what RPM is you A/F mixture experiencing 12.5

[Caprimaniac]

Hi, Priobe/ all.

The 11-12 AF was above 4000.
In the 10's from 2000 when flooring the pedal.

Engine is running fine (but a litle rich) up to 3000.

40 chokes, 165 mains 200 (190) air corr.

Tried 140 mains today: A/F 16 at 5000 rpm.

Changing back to 165 mains, getting larger air corr. later on.
220?
Think moving up more will make A/F too low, since changing 165- 140 made such a difference.

Have to go'n change the mains. Track- day on sunday, mother in law's 50'th anniversary tomorrow....

[priobe]

145 to 165 is a huge change.

I would change to 160

[priobe]

DCMgt,

I dont understand your graph with the formula ( I must be doing something wrong)

By your chart what choke is recommended for a Ford FE 427 motor for HP and Torque.

[DMXF]

Originally Posted by priobe

DCMgt,

I dont understand your graph with the formula ( I must be doing something wrong)

By your chart what choke is recommended for a Ford FE 427 motor for HP and Torque.

Do you have a dyno plot showing what rpm your engine makes peak power? If not, what is your guesstimate of that rpm or where would you like it to occur? Please also confirm whether you have 427 ci and not running a stroker crank.

[priobe]

Scratch my last post

I would change the exhaust valve.

What value is it?

[Caprimaniac]

Originally Posted by priobe

Scratch my last post

I would change the exhaust valve.

What value is it?

Priobe, your question goes to me, right?

Exhaust are blank. 000.

I've been thinking about this; would it work better with an exhaust valve?
I think no; the extra fuel is needed when flooring. Above around 4- 5000 they probably don't make any difference.

Books say and other members say: size 00 exhaust for performance use...
(These ar IDF's, not IDA's....)

[priobe]

caprimaniac,

1 thing I noticed is that by changing the exhaust while driving normal makes a difference. I know many might say this circuit is only for when the pedal is being pressed. Well, I agree with that , however you will be surprised how much you foot will move on the accellerator when you think you are holding the throttle at a certain rate. Dont take my word for it, do this. Go get your self a throttle position sensor. Mount it to the carb body, and use a volt meter to test how still you foot is on the throttle. I am willing to bet that you foot moves creating extra fuel when you think it is completely still.

Then, you can see if you really need different exhaust valves.

If you have a LM1 A/R meter then you are half way there. If not, it will be very difficult to fine your carbs.

With the IDF, they make a mounting bracket for your setup already. So this should be 1,2,3.

If you need help with the wiring let me know.

[priobe]

Dcmgt,

Peak power was made 5800 rpm ( If memory is correct).

It is a 427 Ci

[DMXF]

Originally Posted by priobe

Dcmgt,

Peak power was made 5800 rpm ( If memory is correct).

It is a 427 Ci

Ok, for peak power at 5800, the choke/displ parameter would be about 32. Rearranging the equation and plugging in yields 2*(32*427/25.128)^1/2 = 46.6mm choke diameter if you don't want power to be limited by choke size.

There is a rule of thumb of how much greater the carb bore size should be than the choke and I recall it's around 20% by memory (can't remember whether that was based on diameter or area). So a 46.6mm choke ratio'd up by 1.2 is about 55.9mm carb bore. Now imagine if you wanted peak power more in the 6500+rpm range, you can see how the ideal choke size would approach 50mm and the bore size to go along with that is 58mm........we just went through a similar exercise to what Shelby American/Ken Miles went through to determine carb size when they were developing the big block Cobra race cars.

For you're planned usage, it would probably be ideal to have 48mm IDA carbs bored out to 52mm (a common procedure done by shops I believe like Berg) and run something like 45mm chokes.

[priobe]

Dcmgt,

I see what you are saying and understand,however I dont see this yeilding a significate advantage for the cost of boring the carbs.

Also this sinario would be for max HP not torque. Is this correct?

If so, then in reducing the choke size from 45 to say 42 - 43 may be better for better throttle response coming out of a corner or stop and go driving.

Another thing that I am not clear about is if the camshaft is designed to carry you to a particular RPM range you can actually decrease power by increasing the size of the choke trying to carry the motro to a highr RPM range.

Is this correct?

[DMXF]

That cost-benefit issue rears it's head quite often. I think you can find 45mm chokes to drop right in your 48IDA's. I've heard of guys running stright tubes for chokes at the 48mm bore size, although anything approaching that is not be design and may have side effects.

From numerous dyno plots I've seen comparing carbs (in general) of different sizes, going larger in choke/bore size to a point increases power at all rpm's from at least 3000 on up (so mid range torque and HP increase). Dyno results don't tell you, however, about driveability off idle up through 2000rpm, which suffers as you go larger. So, yes, in most cases smaller carbs will "feel" better in traffic use. If you're up to the challenge, getting the larger carbs to run smoothly at lower engine speeds will give you a stout ride. You would probably have to go real big, beyond practical, to start decreasing power across a wide spectrum of engine speed. But you can try different things for yourself and let us know how well all this fits with your configuration.

[priobe]

Thanks for the post.

I think I will try the 42 which I have on hand then might purchased 45 / 46 mm for giggles.

Finally if that work out for me then I will try no chokes.

I have been playing with these carb for a few years and aquired a very wide range of jets and Etubes so another $100 or so, for extra chokes cant hurt the pockets anymore

[DMXF]

Keep in mind choke size effect probably has limited benefit analogous to other parameters, like cam specs. For example, if you have a bone stock 390 and try putting bigger cams in, the performance increase will likely be marginal. In contrast, if you do the same thing with a Keith Craft built 500+ ci 650hp FE monster, the power difference between a stock 390 cam and a high lift & duration roller will be tremendous. It's more an issue of allowing the engine to make the power and rpm it was designed for rather than it forcing the engine to turn more rpm than it should.

[Caprimaniac]

Ok, Priobe- this have been into my mind as well; so: I will change air jets first and then see. If A/F is OK at wide open, and still around 10- 11 lower in the RPM scale,the exhaust has to be changed. Definitive.

I visited a racetrack last weekend and did alot of testing: In 4., the engine completely stalls at 4000 rpm, no matter what- if you gon on and off then on again; still the same. If you flloor the pedal; no answer either.
But; If revved to 7- 7500 rpm in 3., it hits 5000 or so in 4. and then it goes on (although not too far, the longest straight lets you go like 190 KMH (110- MPH), so I guess maximum 6200 in 4.?).
To be honest, the engine runs like crap, (is it weather- sick? it rained...) and I'm onto trying different things:
- Going to colder plugs
- Reducing the cold air scoop
- Removing closed "pressure box" around the carb air horns
- Using "boxed" K&N filters
(- Larger air jets and mesh filters for the air horns will go in next week)

Thanks for all the feedback

[Caprimaniac]

After alot of testing, this is what has come up;

I've done all of the above, even run NGK 7 plugs now.

The engine run really well above 4000 (up to somewhere... How long can it be stretched?).

It is still hesitating/ grumbling between 2000 and 4000 after braking through a corner and then accelerating. This is because of excess fuel.

Although shifting into 2. gives the punch, I'm convinced that a leaner bottom end will make the car faster as the time used for downshift + upshift will be larger than the time used for accelerate in 3. from 3000 and up...

What will be tried first is:
Use a smaller main fuel jet (from 165 to 145) and a smaller air jet (from 220 to 200). In theory, according to Mr. John Passini (if I read his words correct...?), this will make a leaner low end while keeping the upper end as is. Sounds smart, or?

The 2. choice is to follow Eljaro,Interesting Weber jetting, and use the F15 emultion tubes ("Tubes with bigger diameter for engines with strong vibration or high compression" and "Leaner low end and throttle response")

Runes

[Tomjohnsen]

Hello everyone.

Does any one have any f-19 and/or f-57 tube`s for sale? My carburator is DCOE weber.
If so, please send me a PM or e-mail me at christoffer_johnsen@hotmail.com

In advance, thanks

Tom Johnsen, Norway

[Gaz64]

Rune,

Your two next trial procedures both have merit and both are worth trying even if you are happy with the first outcome.

Back-to-back testing with a stopwatch and/or dragstrip acceleration test with a wideband O2 sensor fitted is also worth the effort.