48 IDA´s - progression holes offset - help wanted

[Rasser]

I have a new set of new 48 IDA´s, but I just noticed that the carbs are not a matched set.....

The problem with my carbs is that when i open the throttle plates on one carb, the 1st progression hole shows immideately (0.5-1.0mm open), but on the other carb the 1st progression hole shows after 1.5-2.0mm. You can clearly see the diffenrence from carb to carb.


I intend to make my engine very streetable and driveable, and I think that the problem with the two carbs not beeing a matched pair will cause some problems when just off idle, and coming into the progression circuit (not going smooth from idle to progression circuit).
Am I right, or does it have no effect at all ?

One guy told me that it has no effect at all, since once the throttle plate is opened, then the vacuum sucks from all 2 (or 3) progression holes at the same time.
I don´t know what to believe right now - so every input is much appreciated....

Rasmus

[John Rayburn]

Just curious if you backed the idle speed screws all the way out on both carbs before you measured?

[Rasser]

Just curious if you backed the idle speed screws all the way out on both carbs before you measured?

Yes, and i made sure that the throttle plates were NOT stuck in the bores.

[Tom G.]

I have same situation on my spanish IDAs with the progression holes fitting....But i hadn´t noticed any problem in driveability...For me driveabiltiy is also very important, because i use the car very often in the city...I use the IDAs (!!34 vents!!) on a 2 litre Type 1 with 35,5x32 valves...
Wunderful driving with such a big monster of carb and such a small valve...
With a wideband (Zeitronix) it has now a wonderful tourque from low rpm to a higher rpm range...

Regards
Tom

[Rasser]

I have same situation on my spanish IDAs with the progression holes fitting....But i hadn´t noticed any problem in driveability...For me driveabiltiy is also very important, because i use the car very often in the city...I use the IDAs (!!34 vents!!) on a 2 litre Type 1 with 35,5x32 valves...
Wunderful driving with such a big monster of carb and such a small valve...
With a wideband (Zeitronix) it has now a wonderful tourque from low rpm to a higher rpm range...

Regards
Tom

Now that´s funny, my carbs are going on my 2 litre Type 4, and also using 34mm vents!

Anyway - I appreciate your input. I will try to put them on the way they are now. If I end up having problems, I might have to plug the old progr. holes and drill new ones - It should be possible....

[Bruce]

One guy told me that it has no effect at all, since once the throttle plate is opened, then the vacuum sucks from all 2 (or 3) progression holes at the same time.

If that were true, the progression holes wouldn't be stacked vertically.  There would be just one big one.  Look at a DRLA, not only are they stacked vertically, they get progressively smaller as you go up.

I wouldn't even try them.  Take them back to where you bought them for an exchange.  Maybe they have another "pair" like yours.

[Rasser]

One guy told me that it has no effect at all, since once the throttle plate is opened, then the vacuum sucks from all 2 (or 3) progression holes at the same time.

If that were true, the progression holes wouldn't be stacked vertically.  There would be just one big one.  Look at a DRLA, not only are they stacked vertically, they get progressively smaller as you go up.

I wouldn't even try them.  Take them back to where you bought them for an exchange.  Maybe they have another "pair" like yours.

I won´t even tell you the guy´s name, but he is VERY well known within the Volkswagen scene.

But I get your point with the progression holes, off course they didn´t make them like that just for fun. I will see if I can modify the bad carb, and drill new progression holes. There are not a lot of space inside the progrssion channel, but I will see if it can be done.
Otherwise I will have to spend 150$ on shipping + 1 month of waiting for the new carb. (those of you living in California are so lucky, you can just drive down to your local shop and exchang the bad parts.) 

[Bruce]

....... once the throttle plate is opened, then the vacuum sucks from all 2 (or 3) progression holes at the same time.

This is simply wrong.

If your throttle plate is in a position such that the lower progression hole is below it, emulsified FUEL will be drawn OUT of it by manifold vacuum.  At that same time, AIR is being drawn IN the progression holes that are ABOVE the throttle plate.  Raise the throttle plate a bit more, the holes formerly allowing AIR into them will allow fuel to flow out, if they are then below the throttle plate.

I predict you will spend $600+ for a new carburator once you ruin the one you have.

[Rasser]

I predict you will spend $600+ for a new carburator once you ruin the one you have.

Thanks for believing in me and my 1m drill.

[Petter Carlberg]

Check that the plates are fixed correct on the axels, this can cause problems like yours. And yes, this is absolutly critical for driveability!
Are they Spanish?

[Rasser]

Check that the plates are fixed correct on the axels, this can cause problems like yours. And yes, this is absolutly critical for driveability!
Are they Spanish?

I have checked that the plates on both carbs were at the exact same position, and the plates are exactly like they should be on both carbs, and close similar etc. etc.  problem is simply that the position/distance of the throttle shaft and progression holes are not the same o both carbs.

Thanks for your input, and yes they are spanish. They actually look to come from two different molds, also have different production numbers, and one is stamped with REDLINE, other carb is not. This one carb is completely junk.
I was just out in the garage again testing and measuring, and it turns out that there are also problems with the idle mixture screws as well.... as if the problems with the progression holes weren´t enough.
The idlemixture-screws wouldn´t seat properly in this one carb. I then found out that the threads for the screw, and the seat that the screw sits in, is offset. This caused the tips on the idlemixture screws to bend  because the screws didn´t go straight on/into the seat. On the other carb everything was fine, and they went straight in, and you could easliy feel with your fingers when they hit the seat.
Man did I get one crappy carb!!!!!!

I miss my old Dellorto´s, they were old - but everything worked flawless. These crappy IDA carbs are killing me!!!!

This junk carb is beeing sent back to California this monday.

[Bruce]

It might be a good idea to send both back, marking the good one.  Then give instructions on how to identify a match.  Otherwise, you might get another dud.