so after much reading about the 48 IDA I plan to put in the 3rd progression hole soon, my problem here is that I cannot find a recommendation or even better first hand experience on what size of a drill bit i need to find so i can add in the 3rd progression hole to my 48 IDA.

 

I have set of drill bits from harbor freight. I just use whatever is the closest or the most similar in size to the orig progression hole. When your drilling, be sure to either remove the butterflies or keep it at WOT. Again be sure not to damage the butterflies.

 

I removed the brass plug on the opposite side of the holes...or was it the mixture screws? Its been a while.

 

well, you have to remove the mixture screw and then the plug below it.

 

all the drill bits i have are way too big, the smallest i currently have is probably twice the size of the orig progression holes,
Wacky, whats the size range of the kit you have from harbor freight? so i can get a similar set.

 

you have to use either an "index" or "number" drill set.

 

YO!

I meassured the original progression holes to be 0.8 mm , i love metrics . -

Be certian that your drill accepts that small of a bit , a quality bit usually have a larger diametre in the end , remember to place the 3d hole where you actually want it , follow the " HOW TO " on this link ,

http://www.vwtrendsweb.com/tech/0308...ce_weber_carb/

Also , the idle jet size needed when 3d hole is done , usually will drop in size , along with some adjustment to the idle mix screws .


IDA power , the rotary loves it ,

Currently running my 12a full bridge , carbons , 48 ida , strong allready from low rpms , kicks at wot .

 

Rotary Alx


that is what i have been looking for thank you!

I used a very similar walk through at http://aircooled.net/gnrlsite/resour...idarebuild.htm
looks to be very similar if not the same, i used to have the link you posted but lost it due to computer issues, and couldn't remember where it was


I am off to order/find some 0.8 mm bits thank you again as now I can finish the IDA with out guess work, this is the only detail they leave out of the walk through.

again thank you for this info as it saves time and money by eliminating trial & error when ordering the bits:icon_ tup:

 

Most reputable shops only charge 20 bucks to do this mod and if you have never done it before you can get yourself in trouble and those little drill bits are f-ing expensive. Good luck.

 

They are cheap $15 for a whole set.
http://www1.mscdirect.com/CGI/NNSRIT...MT4NO=45290364

I did mine by self no problems very easy mod. I also bough a little small drill bit holder that I chucked up in the drill press again very cheap.

 

Yup, they're not expensive. you should get the index and number drills sets (#40's - 80's). I use them a lot for drilling out jets. Makes tuning easier. Besides, you cant use them VW specs so at least use it for a good cause.

 

I'll try this mod too.

 

Does some know where exactly to put this hole.

 

Remove the 2 plug including the venturies and the needle screws. grab the bell crank and turn it to WOT. this is to ensure that you dont damage the venturies and butterflies. Hand free drilling is ok but drill press is better.

 

Thanks Wacky,
Till there everything was clear for me. (Sorry for that imprecise question.)

Where exactly should I drill that damn hole compared to the 2 existing
Closer to the top or the bottom one?
Is the location important?

By the way, what do think about removing that wall inside the carburettor body to enlarge the fuel chamber?
http://www.vwtrendsweb.com/tech/0308...r_carb_part_3/

 

its doesnt matter where the 3rd progression hole goes provided the 2 new holes are in similar spot.

I've done the fuel bowl mod. An extra 1 or 2 ounces of extra gas helps and its is less costly than extending the fuel bowl. Be sure to have a 300 needle/seat (or glass ball) and a good regulator. Jack of Jay-Cee enterprises recommends a "moroso fuel log" (not as expensive as the mallory but works as good) over the typical regulator such as a holley or mallory. He had good experience with it in his race VWs. I still need to install mine so I dont have any hands-on experience but Jack knows his ****.

 

I have a 300 needle/seat (or glass ball).

I never used a fuel regulator.
I have 2 low pressure fuel pumps in parallel, that can be switched on an off manually.
One is the main pump and it’s always running.
If the fuel level gets low in the fuel tank or if the main pump should fail, I can switch to the reserve pump. (Remember that I run 4 hour endurance races. All the important parts are doubled on my car.)
These fuel pumps are specially designed for Weber carburettors; they provide a maximal pressure of 0.35 bar (5.076psi) and stop running if the maximum pressure is reached.

I’ll do the carb conversation today (wall and 3rd hole).
I’ll keep you informed.

 

I just finished the modification.
The third progression hole.

 

nice...I like the fuel pump idea also ala old school racing beat's dual facet system. but I cant remember if RB used a facet's 6psi or the low-pressure.

 

The fuel bowl mod.

 

Some more pictures.

 

Forgot to ask.

Which idle jets should I use with this setup, for a full bridge ported engine?

 

around 80 since there's so much more overlap and the motor sucks more gas.

 

Thanks for the info.
I have to rebuild the engine first, than I can start playing with the jets.

Here how a broken (low compression) bridge ported engine sounds like. http://www.youtube.com/watch?v=0DdYcZWZur0

 

looking good Tomasoft, i wish i had a drill press & thanks for the pics

I had to go free hand when drilling the 3rd progression holes, all went very well for me, and the IDA has become a rotary friendly carb, simply amazing how much of a difference this makes.

I found with this mod and some super sized pump jets that i can now run much larger choke tubes, prior to the new progression holes, and new pump jets i was playing with 37 mm chokes and still had all sorts of problems, now i have it very streetable with 42's only a flat spot if you get too excited and open them up too quick,my tunning is for a 12a large street port, and I now realize what people mean when they say this carb rules