44 IDF's

Gaz64 · #1 (**permalink**) 03-22-2009, 03:48 AM

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 · #2 (**permalink**) 03-22-2009, 11:00 AM

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 · #3 (**permalink**) 04-06-2009, 07:12 AM

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.

Jac Mac · #4 (**permalink**) 05-11-2009, 12:38 PM

Quote:

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 · #5 (**permalink**) 05-15-2009, 06:14 PM

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 · #6 (**permalink**) 05-15-2009, 09:31 PM

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.

Gaz64 · #7 (**permalink**) 05-16-2009, 01:48 AM

race-it, listen to Eljaro, he is THE Weber guru, check out his posts.

A/F ratio with carbs has a lot to do with cam profile etc.

Valve overlap has exhaust AND fresh air/fuel mix going down the pipes, the more overlap, the more this happens.
The air/fuel going out at overlap doesn't combust very well being mixed with exhaust gas.
Leads to high hydrocarbon and high CO emission levels.

Unavoidable with carbs and big cams, more easily controlled with sequential EFI.

My V8 runs 14.2 at idle yet smells of fuel at idle and burns your eyes if you're behind it up close.

race-it · #8 (**permalink**) 05-11-2009, 09:51 AM

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