44 IDF's

[albanycobra]

Hey Guys I just fitted a brand new set of 44IDF's to my FFR Coupe
I am having some trouble which I'm hoping someone can help me with.

Ok I balanced carbs, so are all good. Set ignition timing to 14 deg.

Now the problems......

1st My front passenger carb does not seem to working like the others.
The other 3 carbs only need 1 3/4 turns out of the mixture screw to run happy but the front carb needs 3 or so turns out before it will do anything. I checked the idle jets and they all the same in the carbs. I have also blown through the idle circuit and all is clear.

2nd the front drivers carb, one of the barrels does not seem to be doing anything. You can turn the mixture screw as many times as you like and nothing changes but on the same carb the other mixture screw works fine.

I'm suspecting vacuum leaks but not sure. Driving the car it seems to go great it revs fine but only after about 1800rpm or so. Up to 1800rpm it sneezes back through the intake. While driving if you rev the engine then let the engine wind down as you slow down it pops and crackles out the exhaust.

Idle jets 50
mains 135
F11
bleeds 200
Stock standard 5.0 converted from EFI to Webers with twin side pipes.

Hoping for some guidence...

[Rick Parker]

After checking for air leaks at the mounting base and assuming the carbs are all syncronized and drawing the same amount of air. Be certain the float level is correct in that carb. Totally investigate the idle circuit. Remove the carb, empty the fuel, remove the idle mixture screw and jets. Check for foreign material at the bottom of the idle jet bore and all passages leading to the idle discharge hole in the Throttle Bore and in all fuel jets. View through the jets while looking at a light source to be sure they are open, look at the air correctors too. Blow compressed air gently through all passages. Reassemble and give it a try.

[Gaz64]

Originally Posted by Rick Parker

After checking for air leaks at the mounting base and assuming the carbs are all syncronized and drawing the same amount of air. Be certain the float level is correct in that carb. Totally investigate the idle circuit. Remove the carb, empty the fuel, remove the idle mixture screw and jets. Check for foreign material at the bottom of the idle jet bore and all passages leading to the idle discharge hole in the Throttle Bore and in all fuel jets. View through the jets while looking at a light source to be sure they are open, look at the air correctors too. Blow compressed air gently through all passages. Reassemble and give it a try.

And while you're doing all of the above, swap two carbs around, if the fault moves with the carb, it's a carb issue, if it stays where it was it's a manifold/cylinder issue.

These days, even brand new Webers out of the box, need cleaning out before use. I have never used a carb out of the box, have done as mentioned above, don't trust anybody, especially a machine.

[More Power]

I am curious what type of throttle linkage you are using. I dealt with one set-up that used the throttle shaft of the left rear carburetor to pull open the other three carburetors. The result was that the engine could rev up to about 3000 rpm on the left two carburetors before it ever opened the right side carburetors. This created a terrible stumble / running condition.

Troy Patterson

[albanycobra]

I swapped carbs around and the problem is following the carb...so at least I know were to look. These are bloody brand new carbs.....wish I could send them back.

I pulled the offending carb off ,throughly cleaned it out with compressed air
and refitted with no change. I don't know what to do now. I thought I was dealing with a vac leak but now I think I have a dodgy carb.

I have a centre pull linkage, works well.

[Gaz64]

That's good in way that you have proved it is a carb problem.
Better than a manifold or cylinder problem.

It does seem odd if you have blown the passages clear and can't see the reason, I'd strip two carbs and do the same compressed air test on both, I'd also blast some fuel through the passages so you can see the flow discharge.

Swap the idle jets between carbs as well.

Don't get fuel in your eyes, it hurts like hell.

If none of the above helps, take the offending carb back to your supplier and see if they can help you.

[albanycobra]

Cheers for the help.
I bought these carbs a year or so ago and just left them in my closet at home.

The carb behaves like it has a vac leak but nothing I do changes it's behavior.
I have 2 good carbs ,one half working carb and one dead carb.

I have swapped jets, swapped floats, you name it. EFI was so much easier.
.

[Jac Mac]

Take the whole four carbs off, turn em upside down, remove all the throttle blade ( Idle speed ) adjuster screws and close each pair of throttle blades-- note the closed position in relation to the port with the idle mixture screws. They should all be a similar distance & the thottle blade/s of your problem carb may need to be repositioned in the shaft to obtain the correct idle mixture port/blade relationship. Shouldnt happen, but it does. There is a cure--- its called H****Y.

[albanycobra]

Also something else I noticed was that some of the carbs you can put your hand on the ram tube and the engine will stall, others you can leave your hand on them and all that happens is loud popping noise in exhaust.....anyone want some cheap webers????

[68gt500]

Originally Posted by albanycobra

Also something else I noticed was that some of the carbs you can put your hand on the ram tube and the engine will stall, others you can leave your hand on them and all that happens is loud popping noise in exhaust.....anyone want some cheap webers????

Ahhh, you are not about to give up - are you?

Restricting the flow by hand is like doing the "manual synchrometer" test ...

Can you tell if the amount of air flowing thru the live & dead is the same?

When you put your hand over the intake, you are actually richening up that cylinder. This over rich mixturte will not burn in the cylinder, but will in the exhaust. That is the popping you are hearing.

It would seem to me that the "dead" ones are not flowing enough air. You need to open those throttle plates a little further.

You should have or borrow a synchrometer, it will let you set the airflow of each carb, so you have equal flow thru all of them.

[albanycobra]

Got the meter and it reads #6 at about 800rpm.

I think I may have blocked or restricted idle circuits ( you might be right Rick), even though I have blown the hell out of the carby ports. I pulled the idle jet and mixture screw out one of the good carbies and one that was not responding, then I sprayed WD40 into the ports and watched the flow out of the mixture screws. There was a notable difference idea came from good friend Cobber (Andy).

I want to tune these webers not repair them. Will try high pressure air again tomorrow and see how it goes.

[albanycobra]

Ok Here's the latest on my Weber saga.....

We cleaned out carbies found one blocked idle jet, Refitted everything
and still a major difference in carby response......anyway we decided to ignore setting idle screws to the same amount of turns and set each cylinder untill it picked up. Some cylinders needed only a turn and a half others needed nearly 3 turns but all cylinders where finally firing and the engine is idling as smooth as stocker should. We decided to drive the car and see what would happen.

Out on the road under light load we could here the carbs coughing back or sneezing through the intake. The car drove really well, if you put your foot down the engine will rev all the way to 5500rpm smoothly and with out hesitation or back firing / sneezing, Stamping on and off the throttle was awesome with no flat spots. What a great noise.

So all I need to do is sort the low speed/light load sneezing and the engine tune is sorted.

I think I need to go richer with the idle jets but when you hold the throttle open and the engine free revs at approx 1200rpm the exhaust makes a popping noise which indicates rich.

[ceslaw]

Dave:

Any update to report? I have been following your progress and we are right now in the same position as you. Idles fine, accellerates nicely, but pops and backfires under light load, more so in the 'transition zone' between 2500 - 3000. I am convinced it is an adjustment problem / jetting problem, but have not gotten around to experimenting with it yet. We were just glad to get it idling well. Curious as to your outcome.

Chuck

[Gaz64]

Dave,

What idle jet are you running?

Example 60F8, 60 is fuel, F8 is idle air bleed, you may only need to change the "F" number if you're happy with idle, the F number affects the transition circuit.
This of course means a new idle jet since they are one part unlike an IDA which is two separate parts.

[zimmy]

Sounds to me that your idle jets are too small. Definitely try the 60s or even 65. The sneezing under light load is an indication of small jets as is the poping in the pipes.

[albanycobra]

I was not having any noticable changes with small jet changes so I got some jet drills and drilled out a set of idles so I would have like a 90 size idle jet.
Put them in the car and it drives great with good low throttle response and the sneezing has just about disappeared only a slight random sneez that you cant feel but you just hear. The mixture screws are still different.

When my car was getting painted I removed my webers and I noticed that when you turned them upside down to check the throttle plate to signal hole
gap there was a big difference bewteen carbs. A good carb had the throttle closed and you could not see the signal (progression holes) and the bad carbs you could see the hole, I have just refitted my carbs and later this week will try another tuning session.

[race-it]

Let me know how you make out. I have similar issues with my 44's. Some sneezing and backfire at low throtle and decilleration. I changed from 55 to 60 idle jet. My mixture screw was 1/2 out instead of the recommended 1 full turn out. Thought I would check out plugs for heat range. I am using Champion 3025's. Waiting to hear if another plug is better?

Jim

[Jac Mac]

Originally Posted by albanycobra

I was not having any noticable changes with small jet changes so I got some jet drills and drilled out a set of idles so I would have like a 90 size idle jet.
Put them in the car and it drives great with good low throttle response and the sneezing has just about disappeared only a slight random sneez that you cant feel but you just hear. The mixture screws are still different.

When my car was getting painted I removed my webers and I noticed that when you turned them upside down to check the throttle plate to signal hole
gap there was a big difference bewteen carbs. A good carb had the throttle closed and you could not see the signal (progression holes) and the bad carbs you could see the hole, I have just refitted my carbs and later this week will try another tuning session.

Dave & Race it.
Your problems with progression/transition hole position variations is not a new one, this article from a 1960's manual shows how to correct the issues. Not for the faint hearted or unsteady hand. Nothing different to what most carb 'experts' have been doing for the last four or five decades really. Many people simply bolt on a replacement carb & if they are lucky the problem disappears, but they never really work out why. With the webers & due to their cost & 'name' people seem to think they should be better-- Sorry, not so!! Read up on it, understand it, & get to work!!

[race-it]

What is the relationship between Air/Fuel ratio and rich or lean. For example: My air /fuel ratio at idle (900 RPM) reads 13 to 14, Yet my car bleeds fuel into my exhaust and backfires in pipes? I understand 14 AFR is a good number? AT the carb shop they said to go from a 50 to a 40 in the accelirator pump discharge. Does this make sense to minimise fuel going to exhaust. I am trying to set carbs for stop light to stoplight performance. Since most of my driving is under 70MPH I do not care about going 100 or more.

[Eljaro]

I do not know if the IDF's are much different than the IDA's, but I had on one body one side drawing more vacuum than the other. It had a twisted throttle plate shaft. I twisted the shaft back to to get both throttle plates in the same position both sides.
You also have to remove all the idle set screws except one. You may have some carb resting on the idle screw without you noticing and the throttle plates not closing completely on that one.
The float level is also important to check. The Webers out of the box are often misadjusted and need some attention.