For all the people with IDA carbs who want to add a 3rd progression hole to fix the stumble problem, do so with caution. I think I ruined my carb. I added the 3rd hole with a 1/16th bit and I think it's just too big. the only other changes made to the carb was int inlet mod and the float bowl extetion wacky does and all new gaskets. Now the car will only run on the pump jet spray and the main circuit. I read for a few months before I decided on weather to do it and now I wish I didn't. most the threads here don't list the size but they say to use the same size as the holes that are already there. I couldn't find any bits smaller than 1/16th not even at the hobby shop by my house so I went with it since it was only a tiny bit bigger than the existing progression holes. now the car will barely drive and my af gauge shows it all the way lean. I tried swaping up to a 75 idle and it starts and runs now but barely. I took an old jet and drilled it out to 125 and it was too rich to drive. one thing is different though, the float bown drain plug broke off when it was comming out so I got it out and put a normal bolt in. I noticed that the ida bolt was hallow like a banjo bolt. Does this bolt control fuel to the idle circuit, could this be my problem?

 

Break out the JB Weld

EDIT: Also, tell me more about the stumble with the stock IDA carb. My OER had the 3rd hole already cast.

 

so I just drove it and funny thing is that the freeway stumble the additional progression hole is supposed to fix is 99% gone I just can't get it to run below 2.5k rpm. does jb weld breakdown in gasoline and oil?

 

I got holes in my carb plugged with JB Weld.

 

no JB weld wont break down. Just be sure to mix your parts equal no more no less. I wouldnt suggest the fast curing stuff either.

 

I'm still waiting for wacky, 680, and drivefast to chime in. I have 2 weber books and neither of them mention anything about the drain plug and why it's a bango style bolt.

 

There's one specifically used for sealing alluminum, like for the pport water jackets etc. As for the progression hole, it sounds like something else is wrong unless you drilled the hole in the wrong spot or crooked. When you did the float bowl mod did you make sure you got all the shavings and metal out of the carb? Make sure all your jets are clear and your float is set correctly. It doesn't take much when taking the carb apart to mess up the float level-those floats are delicate. If all that checks out then I would plug the hole that you made with an alluminum sealer and see if that fixes the problem and go from there.

 

Have you added a progression hole before? Was 1/16" too big?

 

No, I have never done it but I heard that if you don't do it right you can mess it up. Most shops only charge 20 bucks to do the mod. 1/16 sounds too big. Those holes are tiny. How does your car idle? Those holes should not effect idle.

 

that's what I've read but there isn't one shop in my area that even touches weber carbs. it won't idle at all normally... I have the idle screws turned out 5 turns and it will only idle at 2k plus it's so lean it's completely off of my af guage. I think its sucking air through the progression hole leaning out theidle circut mixture too much. once im past those wholes and the main circuit comes on it runs great. im going to take the carb apart again tomorrow and try and clea it out more. I need to figure out if using a regular screw in the float bowl drain plug is an issue or not. the float is set right so I know that's not the issue. when you think ablout it no matter how big the progresson hole is it shouldn't mess up the idle at all. but for some reason its just not getting fuel to the idle circuit.

 

if it wont idle below 2500 rpm, progression hole has nothing to do with it. before anything, find out why the butterflies are open. binding in the linkage particularly the cam (including pump rod inside) under the carb

sorry I have been around

 

Adding the third prog hole , at its correct position , usally results in a richer idle mixture , so when u now experience a leaner idle mixture and exessive high idle rpm , somethings either blocking the fuel on its way , or you got false air entering somewhere . 5 turns out on the screws ? Mabye thats where the air gets in and destroys the "fuel vacume signal " from sucking fuel out the prog holes/ idle circut.


The idle mix screws only got a short " work range " before the sharp metering edge of the screw is turned to far out , leaving only the threads left .

So the idea is to use a large enough idle jet , so that you still have some adjusting left on the mixture screw edge to do the fine tuning . Not having yo use only the 0.5 increase/decrease in jet size .

 

last i checked jbweld will slowly dissolve in gasoline. the package says it's not impervious to gas.

devcon aluminum putty is gasoline resistant and i've used it on carbs before.

the float bowl drain plug is just a plug. it's hollow so it'll hold some more gas. and crud on the bottom of the float bowl tends to accumulate in that plug.

if it's running lean after this attempted modification then more air is getting in there somehow (or less fuel). are the plugs for the progression holes not sealed? throttle blades off?

http://www.mcmaster.com/ has tiny metric drill bits. i've bought them sized .55mm up to .80mm in increments of .05mm to enlarge the accelerator pump jets on my ida.

cbperformance.com sells jet measuring kits which could have been used to determine the progression hole size. a must for any carb owner doing their own tuning.

good luck, hope it works out.

 

k so I took it apart and im taking it in for a bath abd getting it blown out at a local shop. I guess ill just boost prep it and make sure everything is all sealed up and tight before I put it back together. I can turn down the idle below 2500 but its too lean to run there so it dies below 2000. i m thinking that somewhere there might be some metal shavings stuck from taking out the bowl wall. and they're not letting fuel get through the idle circuit. I just blew it all out with carb cleaner and they seemed to flow fine. I still think that the added hole is leaking air into the idle circuit when the carb is under vacuum. im going to see if they can soder the holes shut then redrill them at 1mm, or 1/24". I checked cb and they only have the big feelers left and they're out of the reamers...

 

I brought my carb to my guy and he said the bigger hole is only going to cause a fat spot on the transition and it isn't the issue. He's going to dip the carb then blow out the passages clean and then fix my chokes. Some idiot put 38 mm chokes in my carb. So I couldn't decide between 42mm and 44mm chokes so were doing a custom grind of 43. lol. hope those are too big! peak tq at 7k FTW!

 

Well I got the carb back all shiny and clean and threy it on the car and the peolem was still there. So I ripped it off and spent 4 hours trying to soder the 3rd progression holes shut!! That was hell the soder just wouldn't stuck to the carb body... I finally managed to make it work, and now it drives fine, so the problem was 100% the added holes. If you're going to do it use a 1mm drill bit and make sure it is 100% straight and that both are in the correct position. On a happier note, I put the 43mm chokes in and what a damn difference. I need to rejet it now because I went from getting 13:1 at WOT to 18:1. lol Big chokes FTW!
I was using 205 mains and 175 a/c
I'm going to try some 220's with 140's

 

I was going to suggest solder since it can be redrilled. Works good for resizing jets instead of buying an assortment of over priced ones. Owning a set of jet sizing probes and bits are a must.

 

Wow. So I put in my Wacky 43mm chokes(pun intended) and my God it woke my engine up. With 220mains and 120 ac it still wants more fuel above 6k RPM! I need to get back on the dyno and see what the TQ curve looks like now. I better get 160 WHP out of this thing before I trash this engine...

 

Main jets effect the entire range, but mainly mid range. Air jets mainly effect top end, so if you are running lean on the top end try going down a couple on the airjets till you get around 13.2-13.5afr at WOT on the top end. You must have drilled the third progression hole incorrectly because that should have not effected idle.

PS. Wacky has been telling you guys to use the bigger chokes from day one and no one listens to him, excpet the few guys that are now making power. It pays to listen to the old farts. LOL

 

lol. the hole was too big and it was causing a vacuum leak at idle...

 

what motor are you running?

 

13B small streetport

 

Update:
I rebuilt the carb and sealed up the 3rd progression holes. After letting them cure I added them again but this time with a 1mm drill bit instead of the 1.58 I used before. Great results the car drives better than before. It's leaner through the idle circut, but the transition is much better. I recomend it to any IDA user but I suggest you use a 0.8mm drill bit aka 0.031496 inchs. Take your time to make sure the drill bit is straight and that both holes are positioned in the exact same spots or you will have troubles. For those who are following my emulsion tube thread. These changes were made before I started playing with the new tubes.